memory: emif: handle frequency and voltage change events

Change SDRAM timings and other settings as necessary
on voltage and frequency changes. We calculate these
register settings based on data from the device data
sheet and inputs such a frequency, voltage state(stable
or ramping), temperature level etc.

TODO: frequency and voltage change handling needs to
be integrated with clock framework and regulator
framework respectively. This is not done today
due to missing pieces in the kernel.

Signed-off-by: Aneesh V <aneesh@ti.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Benoit Cousson <b-cousson@ti.com>
[santosh.shilimkar@ti.com: Moved to drivers/memory from drivers/misc]
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 891 insertions, 3 deletions

diff --git a/drivers/memory/emif.c b/drivers/memory/emif.c
index 7486d7e..bd116eb 100644
--- a/drivers/memory/emif.c
+++ b/drivers/memory/emif.c
@@ -21,6 +21,7 @@
 #include <linux/seq_file.h>
 #include <linux/module.h>
 #include <linux/list.h>
+#include <linux/spinlock.h>
 #include <memory/jedec_ddr.h>
 #include "emif.h"
 
@@ -37,20 +38,595 @@
  * @node:			node in the device list
  * @base:			base address of memory-mapped IO registers.
  * @dev:			device pointer.
+ * @addressing			table with addressing information from the spec
+ * @regs_cache:			An array of 'struct emif_regs' that stores
+ *				calculated register values for different
+ *				frequencies, to avoid re-calculating them on
+ *				each DVFS transition.
+ * @curr_regs:			The set of register values used in the last
+ *				frequency change (i.e. corresponding to the
+ *				frequency in effect at the moment)
  * @plat_data:			Pointer to saved platform data.
  */
 struct emif_data {
 	u8				duplicate;
 	u8				temperature_level;
+	u8				lpmode;
 	struct list_head		node;
+	unsigned long			irq_state;
 	void __iomem			*base;
 	struct device			*dev;
+	const struct lpddr2_addressing	*addressing;
+	struct emif_regs		*regs_cache[EMIF_MAX_NUM_FREQUENCIES];
+	struct emif_regs		*curr_regs;
 	struct emif_platform_data	*plat_data;
 };
 
 static struct emif_data *emif1;
+static spinlock_t	emif_lock;
+static unsigned long	irq_state;
+static u32		t_ck; /* DDR clock period in ps */
 static LIST_HEAD(device_list);
 
+/*
+ * Calculate the period of DDR clock from frequency value
+ */
+static void set_ddr_clk_period(u32 freq)
+{
+	/* Divide 10^12 by frequency to get period in ps */
+	t_ck = (u32)DIV_ROUND_UP_ULL(1000000000000ull, freq);
+}
+
+/*
+ * Get the CL from SDRAM_CONFIG register
+ */
+static u32 get_cl(struct emif_data *emif)
+{
+	u32		cl;
+	void __iomem	*base = emif->base;
+
+	cl = (readl(base + EMIF_SDRAM_CONFIG) & CL_MASK) >> CL_SHIFT;
+
+	return cl;
+}
+
+static void set_lpmode(struct emif_data *emif, u8 lpmode)
+{
+	u32 temp;
+	void __iomem *base = emif->base;
+
+	temp = readl(base + EMIF_POWER_MANAGEMENT_CONTROL);
+	temp &= ~LP_MODE_MASK;
+	temp |= (lpmode << LP_MODE_SHIFT);
+	writel(temp, base + EMIF_POWER_MANAGEMENT_CONTROL);
+}
+
+static void do_freq_update(void)
+{
+	struct emif_data *emif;
+
+	/*
+	 * Workaround for errata i728: Disable LPMODE during FREQ_UPDATE
+	 *
+	 * i728 DESCRIPTION:
+	 * The EMIF automatically puts the SDRAM into self-refresh mode
+	 * after the EMIF has not performed accesses during
+	 * EMIF_PWR_MGMT_CTRL[7:4] REG_SR_TIM number of DDR clock cycles
+	 * and the EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field is set
+	 * to 0x2. If during a small window the following three events
+	 * occur:
+	 * - The SR_TIMING counter expires
+	 * - And frequency change is requested
+	 * - And OCP access is requested
+	 * Then it causes instable clock on the DDR interface.
+	 *
+	 * WORKAROUND
+	 * To avoid the occurrence of the three events, the workaround
+	 * is to disable the self-refresh when requesting a frequency
+	 * change. Before requesting a frequency change the software must
+	 * program EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE to 0x0. When the
+	 * frequency change has been done, the software can reprogram
+	 * EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE to 0x2
+	 */
+	list_for_each_entry(emif, &device_list, node) {
+		if (emif->lpmode == EMIF_LP_MODE_SELF_REFRESH)
+			set_lpmode(emif, EMIF_LP_MODE_DISABLE);
+	}
+
+	/*
+	 * TODO: Do FREQ_UPDATE here when an API
+	 * is available for this as part of the new
+	 * clock framework
+	 */
+
+	list_for_each_entry(emif, &device_list, node) {
+		if (emif->lpmode == EMIF_LP_MODE_SELF_REFRESH)
+			set_lpmode(emif, EMIF_LP_MODE_SELF_REFRESH);
+	}
+}
+
+/* Find addressing table entry based on the device's type and density */
+static const struct lpddr2_addressing *get_addressing_table(
+	const struct ddr_device_info *device_info)
+{
+	u32		index, type, density;
+
+	type = device_info->type;
+	density = device_info->density;
+
+	switch (type) {
+	case DDR_TYPE_LPDDR2_S4:
+		index = density - 1;
+		break;
+	case DDR_TYPE_LPDDR2_S2:
+		switch (density) {
+		case DDR_DENSITY_1Gb:
+		case DDR_DENSITY_2Gb:
+			index = density + 3;
+			break;
+		default:
+			index = density - 1;
+		}
+		break;
+	default:
+		return NULL;
+	}
+
+	return &lpddr2_jedec_addressing_table[index];
+}
+
+/*
+ * Find the the right timing table from the array of timing
+ * tables of the device using DDR clock frequency
+ */
+static const struct lpddr2_timings *get_timings_table(struct emif_data *emif,
+		u32 freq)
+{
+	u32				i, min, max, freq_nearest;
+	const struct lpddr2_timings	*timings = NULL;
+	const struct lpddr2_timings	*timings_arr = emif->plat_data->timings;
+	struct				device *dev = emif->dev;
+
+	/* Start with a very high frequency - 1GHz */
+	freq_nearest = 1000000000;
+
+	/*
+	 * Find the timings table such that:
+	 *  1. the frequency range covers the required frequency(safe) AND
+	 *  2. the max_freq is closest to the required frequency(optimal)
+	 */
+	for (i = 0; i < emif->plat_data->timings_arr_size; i++) {
+		max = timings_arr[i].max_freq;
+		min = timings_arr[i].min_freq;
+		if ((freq >= min) && (freq <= max) && (max < freq_nearest)) {
+			freq_nearest = max;
+			timings = &timings_arr[i];
+		}
+	}
+
+	if (!timings)
+		dev_err(dev, "%s: couldn't find timings for - %dHz\n",
+			__func__, freq);
+
+	dev_dbg(dev, "%s: timings table: freq %d, speed bin freq %d\n",
+		__func__, freq, freq_nearest);
+
+	return timings;
+}
+
+static u32 get_sdram_ref_ctrl_shdw(u32 freq,
+		const struct lpddr2_addressing *addressing)
+{
+	u32 ref_ctrl_shdw = 0, val = 0, freq_khz, t_refi;
+
+	/* Scale down frequency and t_refi to avoid overflow */
+	freq_khz = freq / 1000;
+	t_refi = addressing->tREFI_ns / 100;
+
+	/*
+	 * refresh rate to be set is 'tREFI(in us) * freq in MHz
+	 * division by 10000 to account for change in units
+	 */
+	val = t_refi * freq_khz / 10000;
+	ref_ctrl_shdw |= val << REFRESH_RATE_SHIFT;
+
+	return ref_ctrl_shdw;
+}
+
+static u32 get_sdram_tim_1_shdw(const struct lpddr2_timings *timings,
+		const struct lpddr2_min_tck *min_tck,
+		const struct lpddr2_addressing *addressing)
+{
+	u32 tim1 = 0, val = 0;
+
+	val = max(min_tck->tWTR, DIV_ROUND_UP(timings->tWTR, t_ck)) - 1;
+	tim1 |= val << T_WTR_SHIFT;
+
+	if (addressing->num_banks == B8)
+		val = DIV_ROUND_UP(timings->tFAW, t_ck*4);
+	else
+		val = max(min_tck->tRRD, DIV_ROUND_UP(timings->tRRD, t_ck));
+	tim1 |= (val - 1) << T_RRD_SHIFT;
+
+	val = DIV_ROUND_UP(timings->tRAS_min + timings->tRPab, t_ck) - 1;
+	tim1 |= val << T_RC_SHIFT;
+
+	val = max(min_tck->tRASmin, DIV_ROUND_UP(timings->tRAS_min, t_ck));
+	tim1 |= (val - 1) << T_RAS_SHIFT;
+
+	val = max(min_tck->tWR, DIV_ROUND_UP(timings->tWR, t_ck)) - 1;
+	tim1 |= val << T_WR_SHIFT;
+
+	val = max(min_tck->tRCD, DIV_ROUND_UP(timings->tRCD, t_ck)) - 1;
+	tim1 |= val << T_RCD_SHIFT;
+
+	val = max(min_tck->tRPab, DIV_ROUND_UP(timings->tRPab, t_ck)) - 1;
+	tim1 |= val << T_RP_SHIFT;
+
+	return tim1;
+}
+
+static u32 get_sdram_tim_1_shdw_derated(const struct lpddr2_timings *timings,
+		const struct lpddr2_min_tck *min_tck,
+		const struct lpddr2_addressing *addressing)
+{
+	u32 tim1 = 0, val = 0;
+
+	val = max(min_tck->tWTR, DIV_ROUND_UP(timings->tWTR, t_ck)) - 1;
+	tim1 = val << T_WTR_SHIFT;
+
+	/*
+	 * tFAW is approximately 4 times tRRD. So add 1875*4 = 7500ps
+	 * to tFAW for de-rating
+	 */
+	if (addressing->num_banks == B8) {
+		val = DIV_ROUND_UP(timings->tFAW + 7500, 4 * t_ck) - 1;
+	} else {
+		val = DIV_ROUND_UP(timings->tRRD + 1875, t_ck);
+		val = max(min_tck->tRRD, val) - 1;
+	}
+	tim1 |= val << T_RRD_SHIFT;
+
+	val = DIV_ROUND_UP(timings->tRAS_min + timings->tRPab + 1875, t_ck);
+	tim1 |= (val - 1) << T_RC_SHIFT;
+
+	val = DIV_ROUND_UP(timings->tRAS_min + 1875, t_ck);
+	val = max(min_tck->tRASmin, val) - 1;
+	tim1 |= val << T_RAS_SHIFT;
+
+	val = max(min_tck->tWR, DIV_ROUND_UP(timings->tWR, t_ck)) - 1;
+	tim1 |= val << T_WR_SHIFT;
+
+	val = max(min_tck->tRCD, DIV_ROUND_UP(timings->tRCD + 1875, t_ck));
+	tim1 |= (val - 1) << T_RCD_SHIFT;
+
+	val = max(min_tck->tRPab, DIV_ROUND_UP(timings->tRPab + 1875, t_ck));
+	tim1 |= (val - 1) << T_RP_SHIFT;
+
+	return tim1;
+}
+
+static u32 get_sdram_tim_2_shdw(const struct lpddr2_timings *timings,
+		const struct lpddr2_min_tck *min_tck,
+		const struct lpddr2_addressing *addressing,
+		u32 type)
+{
+	u32 tim2 = 0, val = 0;
+
+	val = min_tck->tCKE - 1;
+	tim2 |= val << T_CKE_SHIFT;
+
+	val = max(min_tck->tRTP, DIV_ROUND_UP(timings->tRTP, t_ck)) - 1;
+	tim2 |= val << T_RTP_SHIFT;
+
+	/* tXSNR = tRFCab_ps + 10 ns(tRFCab_ps for LPDDR2). */
+	val = DIV_ROUND_UP(addressing->tRFCab_ps + 10000, t_ck) - 1;
+	tim2 |= val << T_XSNR_SHIFT;
+
+	/* XSRD same as XSNR for LPDDR2 */
+	tim2 |= val << T_XSRD_SHIFT;
+
+	val = max(min_tck->tXP, DIV_ROUND_UP(timings->tXP, t_ck)) - 1;
+	tim2 |= val << T_XP_SHIFT;
+
+	return tim2;
+}
+
+static u32 get_sdram_tim_3_shdw(const struct lpddr2_timings *timings,
+		const struct lpddr2_min_tck *min_tck,
+		const struct lpddr2_addressing *addressing,
+		u32 type, u32 ip_rev, u32 derated)
+{
+	u32 tim3 = 0, val = 0, t_dqsck;
+
+	val = timings->tRAS_max_ns / addressing->tREFI_ns - 1;
+	val = val > 0xF ? 0xF : val;
+	tim3 |= val << T_RAS_MAX_SHIFT;
+
+	val = DIV_ROUND_UP(addressing->tRFCab_ps, t_ck) - 1;
+	tim3 |= val << T_RFC_SHIFT;
+
+	t_dqsck = (derated == EMIF_DERATED_TIMINGS) ?
+		timings->tDQSCK_max_derated : timings->tDQSCK_max;
+	if (ip_rev == EMIF_4D5)
+		val = DIV_ROUND_UP(t_dqsck + 1000, t_ck) - 1;
+	else
+		val = DIV_ROUND_UP(t_dqsck, t_ck) - 1;
+
+	tim3 |= val << T_TDQSCKMAX_SHIFT;
+
+	val = DIV_ROUND_UP(timings->tZQCS, t_ck) - 1;
+	tim3 |= val << ZQ_ZQCS_SHIFT;
+
+	val = DIV_ROUND_UP(timings->tCKESR, t_ck);
+	val = max(min_tck->tCKESR, val) - 1;
+	tim3 |= val << T_CKESR_SHIFT;
+
+	if (ip_rev == EMIF_4D5) {
+		tim3 |= (EMIF_T_CSTA - 1) << T_CSTA_SHIFT;
+
+		val = DIV_ROUND_UP(EMIF_T_PDLL_UL, 128) - 1;
+		tim3 |= val << T_PDLL_UL_SHIFT;
+	}
+
+	return tim3;
+}
+
+static u32 get_read_idle_ctrl_shdw(u8 volt_ramp)
+{
+	u32 idle = 0, val = 0;
+
+	/*
+	 * Maximum value in normal conditions and increased frequency
+	 * when voltage is ramping
+	 */
+	if (volt_ramp)
+		val = READ_IDLE_INTERVAL_DVFS / t_ck / 64 - 1;
+	else
+		val = 0x1FF;
+
+	/*
+	 * READ_IDLE_CTRL register in EMIF4D has same offset and fields
+	 * as DLL_CALIB_CTRL in EMIF4D5, so use the same shifts
+	 */
+	idle |= val << DLL_CALIB_INTERVAL_SHIFT;
+	idle |= EMIF_READ_IDLE_LEN_VAL << ACK_WAIT_SHIFT;
+
+	return idle;
+}
+
+static u32 get_dll_calib_ctrl_shdw(u8 volt_ramp)
+{
+	u32 calib = 0, val = 0;
+
+	if (volt_ramp == DDR_VOLTAGE_RAMPING)
+		val = DLL_CALIB_INTERVAL_DVFS / t_ck / 16 - 1;
+	else
+		val = 0; /* Disabled when voltage is stable */
+
+	calib |= val << DLL_CALIB_INTERVAL_SHIFT;
+	calib |= DLL_CALIB_ACK_WAIT_VAL << ACK_WAIT_SHIFT;
+
+	return calib;
+}
+
+static u32 get_ddr_phy_ctrl_1_attilaphy_4d(const struct lpddr2_timings *timings,
+	u32 freq, u8 RL)
+{
+	u32 phy = EMIF_DDR_PHY_CTRL_1_BASE_VAL_ATTILAPHY, val = 0;
+
+	val = RL + DIV_ROUND_UP(timings->tDQSCK_max, t_ck) - 1;
+	phy |= val << READ_LATENCY_SHIFT_4D;
+
+	if (freq <= 100000000)
+		val = EMIF_DLL_SLAVE_DLY_CTRL_100_MHZ_AND_LESS_ATTILAPHY;
+	else if (freq <= 200000000)
+		val = EMIF_DLL_SLAVE_DLY_CTRL_200_MHZ_ATTILAPHY;
+	else
+		val = EMIF_DLL_SLAVE_DLY_CTRL_400_MHZ_ATTILAPHY;
+
+	phy |= val << DLL_SLAVE_DLY_CTRL_SHIFT_4D;
+
+	return phy;
+}
+
+static u32 get_phy_ctrl_1_intelliphy_4d5(u32 freq, u8 cl)
+{
+	u32 phy = EMIF_DDR_PHY_CTRL_1_BASE_VAL_INTELLIPHY, half_delay;
+
+	/*
+	 * DLL operates at 266 MHz. If DDR frequency is near 266 MHz,
+	 * half-delay is not needed else set half-delay
+	 */
+	if (freq >= 265000000 && freq < 267000000)
+		half_delay = 0;
+	else
+		half_delay = 1;
+
+	phy |= half_delay << DLL_HALF_DELAY_SHIFT_4D5;
+	phy |= ((cl + DIV_ROUND_UP(EMIF_PHY_TOTAL_READ_LATENCY_INTELLIPHY_PS,
+			t_ck) - 1) << READ_LATENCY_SHIFT_4D5);
+
+	return phy;
+}
+
+static u32 get_ext_phy_ctrl_2_intelliphy_4d5(void)
+{
+	u32 fifo_we_slave_ratio;
+
+	fifo_we_slave_ratio =  DIV_ROUND_CLOSEST(
+		EMIF_INTELLI_PHY_DQS_GATE_OPENING_DELAY_PS * 256 , t_ck);
+
+	return fifo_we_slave_ratio | fifo_we_slave_ratio << 11 |
+		fifo_we_slave_ratio << 22;
+}
+
+static u32 get_ext_phy_ctrl_3_intelliphy_4d5(void)
+{
+	u32 fifo_we_slave_ratio;
+
+	fifo_we_slave_ratio =  DIV_ROUND_CLOSEST(
+		EMIF_INTELLI_PHY_DQS_GATE_OPENING_DELAY_PS * 256 , t_ck);
+
+	return fifo_we_slave_ratio >> 10 | fifo_we_slave_ratio << 1 |
+		fifo_we_slave_ratio << 12 | fifo_we_slave_ratio << 23;
+}
+
+static u32 get_ext_phy_ctrl_4_intelliphy_4d5(void)
+{
+	u32 fifo_we_slave_ratio;
+
+	fifo_we_slave_ratio =  DIV_ROUND_CLOSEST(
+		EMIF_INTELLI_PHY_DQS_GATE_OPENING_DELAY_PS * 256 , t_ck);
+
+	return fifo_we_slave_ratio >> 9 | fifo_we_slave_ratio << 2 |
+		fifo_we_slave_ratio << 13;
+}
+
+static u32 get_pwr_mgmt_ctrl(u32 freq, struct emif_data *emif, u32 ip_rev)
+{
+	u32 pwr_mgmt_ctrl	= 0, timeout;
+	u32 lpmode		= EMIF_LP_MODE_SELF_REFRESH;
+	u32 timeout_perf	= EMIF_LP_MODE_TIMEOUT_PERFORMANCE;
+	u32 timeout_pwr		= EMIF_LP_MODE_TIMEOUT_POWER;
+	u32 freq_threshold	= EMIF_LP_MODE_FREQ_THRESHOLD;
+
+	struct emif_custom_configs *cust_cfgs = emif->plat_data->custom_configs;
+
+	if (cust_cfgs && (cust_cfgs->mask & EMIF_CUSTOM_CONFIG_LPMODE)) {
+		lpmode		= cust_cfgs->lpmode;
+		timeout_perf	= cust_cfgs->lpmode_timeout_performance;
+		timeout_pwr	= cust_cfgs->lpmode_timeout_power;
+		freq_threshold  = cust_cfgs->lpmode_freq_threshold;
+	}
+
+	/* Timeout based on DDR frequency */
+	timeout = freq >= freq_threshold ? timeout_perf : timeout_pwr;
+
+	/* The value to be set in register is "log2(timeout) - 3" */
+	if (timeout < 16) {
+		timeout = 0;
+	} else {
+		timeout = __fls(timeout) - 3;
+		if (timeout & (timeout - 1))
+			timeout++;
+	}
+
+	switch (lpmode) {
+	case EMIF_LP_MODE_CLOCK_STOP:
+		pwr_mgmt_ctrl = (timeout << CS_TIM_SHIFT) |
+					SR_TIM_MASK | PD_TIM_MASK;
+		break;
+	case EMIF_LP_MODE_SELF_REFRESH:
+		/* Workaround for errata i735 */
+		if (timeout < 6)
+			timeout = 6;
+
+		pwr_mgmt_ctrl = (timeout << SR_TIM_SHIFT) |
+					CS_TIM_MASK | PD_TIM_MASK;
+		break;
+	case EMIF_LP_MODE_PWR_DN:
+		pwr_mgmt_ctrl = (timeout << PD_TIM_SHIFT) |
+					CS_TIM_MASK | SR_TIM_MASK;
+		break;
+	case EMIF_LP_MODE_DISABLE:
+	default:
+		pwr_mgmt_ctrl = CS_TIM_MASK |
+					PD_TIM_MASK | SR_TIM_MASK;
+	}
+
+	/* No CS_TIM in EMIF_4D5 */
+	if (ip_rev == EMIF_4D5)
+		pwr_mgmt_ctrl &= ~CS_TIM_MASK;
+
+	pwr_mgmt_ctrl |= lpmode << LP_MODE_SHIFT;
+
+	return pwr_mgmt_ctrl;
+}
+
+/*
+ * Program EMIF shadow registers that are not dependent on temperature
+ * or voltage
+ */
+static void setup_registers(struct emif_data *emif, struct emif_regs *regs)
+{
+	void __iomem	*base = emif->base;
+
+	writel(regs->sdram_tim2_shdw, base + EMIF_SDRAM_TIMING_2_SHDW);
+	writel(regs->phy_ctrl_1_shdw, base + EMIF_DDR_PHY_CTRL_1_SHDW);
+
+	/* Settings specific for EMIF4D5 */
+	if (emif->plat_data->ip_rev != EMIF_4D5)
+		return;
+	writel(regs->ext_phy_ctrl_2_shdw, base + EMIF_EXT_PHY_CTRL_2_SHDW);
+	writel(regs->ext_phy_ctrl_3_shdw, base + EMIF_EXT_PHY_CTRL_3_SHDW);
+	writel(regs->ext_phy_ctrl_4_shdw, base + EMIF_EXT_PHY_CTRL_4_SHDW);
+}
+
+/*
+ * When voltage ramps dll calibration and forced read idle should
+ * happen more often
+ */
+static void setup_volt_sensitive_regs(struct emif_data *emif,
+		struct emif_regs *regs, u32 volt_state)
+{
+	u32		calib_ctrl;
+	void __iomem	*base = emif->base;
+
+	/*
+	 * EMIF_READ_IDLE_CTRL in EMIF4D refers to the same register as
+	 * EMIF_DLL_CALIB_CTRL in EMIF4D5 and dll_calib_ctrl_shadow_*
+	 * is an alias of the respective read_idle_ctrl_shdw_* (members of
+	 * a union). So, the below code takes care of both cases
+	 */
+	if (volt_state == DDR_VOLTAGE_RAMPING)
+		calib_ctrl = regs->dll_calib_ctrl_shdw_volt_ramp;
+	else
+		calib_ctrl = regs->dll_calib_ctrl_shdw_normal;
+
+	writel(calib_ctrl, base + EMIF_DLL_CALIB_CTRL_SHDW);
+}
+
+/*
+ * setup_temperature_sensitive_regs() - set the timings for temperature
+ * sensitive registers. This happens once at initialisation time based
+ * on the temperature at boot time and subsequently based on the temperature
+ * alert interrupt. Temperature alert can happen when the temperature
+ * increases or drops. So this function can have the effect of either
+ * derating the timings or going back to nominal values.
+ */
+static void setup_temperature_sensitive_regs(struct emif_data *emif,
+		struct emif_regs *regs)
+{
+	u32		tim1, tim3, ref_ctrl, type;
+	void __iomem	*base = emif->base;
+	u32		temperature;
+
+	type = emif->plat_data->device_info->type;
+
+	tim1 = regs->sdram_tim1_shdw;
+	tim3 = regs->sdram_tim3_shdw;
+	ref_ctrl = regs->ref_ctrl_shdw;
+
+	/* No de-rating for non-lpddr2 devices */
+	if (type != DDR_TYPE_LPDDR2_S2 && type != DDR_TYPE_LPDDR2_S4)
+		goto out;
+
+	temperature = emif->temperature_level;
+	if (temperature == SDRAM_TEMP_HIGH_DERATE_REFRESH) {
+		ref_ctrl = regs->ref_ctrl_shdw_derated;
+	} else if (temperature == SDRAM_TEMP_HIGH_DERATE_REFRESH_AND_TIMINGS) {
+		tim1 = regs->sdram_tim1_shdw_derated;
+		tim3 = regs->sdram_tim3_shdw_derated;
+		ref_ctrl = regs->ref_ctrl_shdw_derated;
+	}
+
+out:
+	writel(tim1, base + EMIF_SDRAM_TIMING_1_SHDW);
+	writel(tim3, base + EMIF_SDRAM_TIMING_3_SHDW);
+	writel(ref_ctrl, base + EMIF_SDRAM_REFRESH_CTRL_SHDW);
+}
+
 static void get_default_timings(struct emif_data *emif)
 {
 	struct emif_platform_data *pd = emif->plat_data;
@@ -234,10 +810,8 @@ static int __init_or_module emif_probe(struct platform_device *pdev)
 		goto error;
 	}
 
-	if (!emif1)
-		emif1 = emif;
-
 	list_add(&emif->node, &device_list);
+	emif->addressing = get_addressing_table(emif->plat_data->device_info);
 
 	/* Save pointers to each other in emif and device structures */
 	emif->dev = &pdev->dev;
@@ -257,6 +831,18 @@ static int __init_or_module emif_probe(struct platform_device *pdev)
 		goto error;
 	}
 
+	/* One-time actions taken on probing the first device */
+	if (!emif1) {
+		emif1 = emif;
+		spin_lock_init(&emif_lock);
+
+		/*
+		 * TODO: register notifiers for frequency and voltage
+		 * change here once the respective frameworks are
+		 * available
+		 */
+	}
+
 	dev_info(&pdev->dev, "%s: device configured with addr = %p\n",
 		__func__, emif->base);
 
@@ -265,6 +851,308 @@ error:
 	return -ENODEV;
 }
 
+static int get_emif_reg_values(struct emif_data *emif, u32 freq,
+		struct emif_regs *regs)
+{
+	u32				cs1_used, ip_rev, phy_type;
+	u32				cl, type;
+	const struct lpddr2_timings	*timings;
+	const struct lpddr2_min_tck	*min_tck;
+	const struct ddr_device_info	*device_info;
+	const struct lpddr2_addressing	*addressing;
+	struct emif_data		*emif_for_calc;
+	struct device			*dev;
+	const struct emif_custom_configs *custom_configs;
+
+	dev = emif->dev;
+	/*
+	 * If the devices on this EMIF instance is duplicate of EMIF1,
+	 * use EMIF1 details for the calculation
+	 */
+	emif_for_calc	= emif->duplicate ? emif1 : emif;
+	timings		= get_timings_table(emif_for_calc, freq);
+	addressing	= emif_for_calc->addressing;
+	if (!timings || !addressing) {
+		dev_err(dev, "%s: not enough data available for %dHz",
+			__func__, freq);
+		return -1;
+	}
+
+	device_info	= emif_for_calc->plat_data->device_info;
+	type		= device_info->type;
+	cs1_used	= device_info->cs1_used;
+	ip_rev		= emif_for_calc->plat_data->ip_rev;
+	phy_type	= emif_for_calc->plat_data->phy_type;
+
+	min_tck		= emif_for_calc->plat_data->min_tck;
+	custom_configs	= emif_for_calc->plat_data->custom_configs;
+
+	set_ddr_clk_period(freq);
+
+	regs->ref_ctrl_shdw = get_sdram_ref_ctrl_shdw(freq, addressing);
+	regs->sdram_tim1_shdw = get_sdram_tim_1_shdw(timings, min_tck,
+			addressing);
+	regs->sdram_tim2_shdw = get_sdram_tim_2_shdw(timings, min_tck,
+			addressing, type);
+	regs->sdram_tim3_shdw = get_sdram_tim_3_shdw(timings, min_tck,
+		addressing, type, ip_rev, EMIF_NORMAL_TIMINGS);
+
+	cl = get_cl(emif);
+
+	if (phy_type == EMIF_PHY_TYPE_ATTILAPHY && ip_rev == EMIF_4D) {
+		regs->phy_ctrl_1_shdw = get_ddr_phy_ctrl_1_attilaphy_4d(
+			timings, freq, cl);
+	} else if (phy_type == EMIF_PHY_TYPE_INTELLIPHY && ip_rev == EMIF_4D5) {
+		regs->phy_ctrl_1_shdw = get_phy_ctrl_1_intelliphy_4d5(freq, cl);
+		regs->ext_phy_ctrl_2_shdw = get_ext_phy_ctrl_2_intelliphy_4d5();
+		regs->ext_phy_ctrl_3_shdw = get_ext_phy_ctrl_3_intelliphy_4d5();
+		regs->ext_phy_ctrl_4_shdw = get_ext_phy_ctrl_4_intelliphy_4d5();
+	} else {
+		return -1;
+	}
+
+	/* Only timeout values in pwr_mgmt_ctrl_shdw register */
+	regs->pwr_mgmt_ctrl_shdw =
+		get_pwr_mgmt_ctrl(freq, emif_for_calc, ip_rev) &
+		(CS_TIM_MASK | SR_TIM_MASK | PD_TIM_MASK);
+
+	if (ip_rev & EMIF_4D) {
+		regs->read_idle_ctrl_shdw_normal =
+			get_read_idle_ctrl_shdw(DDR_VOLTAGE_STABLE);
+
+		regs->read_idle_ctrl_shdw_volt_ramp =
+			get_read_idle_ctrl_shdw(DDR_VOLTAGE_RAMPING);
+	} else if (ip_rev & EMIF_4D5) {
+		regs->dll_calib_ctrl_shdw_normal =
+			get_dll_calib_ctrl_shdw(DDR_VOLTAGE_STABLE);
+
+		regs->dll_calib_ctrl_shdw_volt_ramp =
+			get_dll_calib_ctrl_shdw(DDR_VOLTAGE_RAMPING);
+	}
+
+	if (type == DDR_TYPE_LPDDR2_S2 || type == DDR_TYPE_LPDDR2_S4) {
+		regs->ref_ctrl_shdw_derated = get_sdram_ref_ctrl_shdw(freq / 4,
+			addressing);
+
+		regs->sdram_tim1_shdw_derated =
+			get_sdram_tim_1_shdw_derated(timings, min_tck,
+				addressing);
+
+		regs->sdram_tim3_shdw_derated = get_sdram_tim_3_shdw(timings,
+			min_tck, addressing, type, ip_rev,
+			EMIF_DERATED_TIMINGS);
+	}
+
+	regs->freq = freq;
+
+	return 0;
+}
+
+/*
+ * get_regs() - gets the cached emif_regs structure for a given EMIF instance
+ * given frequency(freq):
+ *
+ * As an optimisation, every EMIF instance other than EMIF1 shares the
+ * register cache with EMIF1 if the devices connected on this instance
+ * are same as that on EMIF1(indicated by the duplicate flag)
+ *
+ * If we do not have an entry corresponding to the frequency given, we
+ * allocate a new entry and calculate the values
+ *
+ * Upon finding the right reg dump, save it in curr_regs. It can be
+ * directly used for thermal de-rating and voltage ramping changes.
+ */
+static struct emif_regs *get_regs(struct emif_data *emif, u32 freq)
+{
+	int			i;
+	struct emif_regs	**regs_cache;
+	struct emif_regs	*regs = NULL;
+	struct device		*dev;
+
+	dev = emif->dev;
+	if (emif->curr_regs && emif->curr_regs->freq == freq) {
+		dev_dbg(dev, "%s: using curr_regs - %u Hz", __func__, freq);
+		return emif->curr_regs;
+	}
+
+	if (emif->duplicate)
+		regs_cache = emif1->regs_cache;
+	else
+		regs_cache = emif->regs_cache;
+
+	for (i = 0; i < EMIF_MAX_NUM_FREQUENCIES && regs_cache[i]; i++) {
+		if (regs_cache[i]->freq == freq) {
+			regs = regs_cache[i];
+			dev_dbg(dev,
+				"%s: reg dump found in reg cache for %u Hz\n",
+				__func__, freq);
+			break;
+		}
+	}
+
+	/*
+	 * If we don't have an entry for this frequency in the cache create one
+	 * and calculate the values
+	 */
+	if (!regs) {
+		regs = devm_kzalloc(emif->dev, sizeof(*regs), GFP_ATOMIC);
+		if (!regs)
+			return NULL;
+
+		if (get_emif_reg_values(emif, freq, regs)) {
+			devm_kfree(emif->dev, regs);
+			return NULL;
+		}
+
+		/*
+		 * Now look for an un-used entry in the cache and save the
+		 * newly created struct. If there are no free entries
+		 * over-write the last entry
+		 */
+		for (i = 0; i < EMIF_MAX_NUM_FREQUENCIES && regs_cache[i]; i++)
+			;
+
+		if (i >= EMIF_MAX_NUM_FREQUENCIES) {
+			dev_warn(dev, "%s: regs_cache full - reusing a slot!!\n",
+				__func__);
+			i = EMIF_MAX_NUM_FREQUENCIES - 1;
+			devm_kfree(emif->dev, regs_cache[i]);
+		}
+		regs_cache[i] = regs;
+	}
+
+	return regs;
+}
+
+static void do_volt_notify_handling(struct emif_data *emif, u32 volt_state)
+{
+	dev_dbg(emif->dev, "%s: voltage notification : %d", __func__,
+		volt_state);
+
+	if (!emif->curr_regs) {
+		dev_err(emif->dev,
+			"%s: volt-notify before registers are ready: %d\n",
+			__func__, volt_state);
+		return;
+	}
+
+	setup_volt_sensitive_regs(emif, emif->curr_regs, volt_state);
+}
+
+/*
+ * TODO: voltage notify handling should be hooked up to
+ * regulator framework as soon as the necessary support
+ * is available in mainline kernel. This function is un-used
+ * right now.
+ */
+static void __attribute__((unused)) volt_notify_handling(u32 volt_state)
+{
+	struct emif_data *emif;
+
+	spin_lock_irqsave(&emif_lock, irq_state);
+
+	list_for_each_entry(emif, &device_list, node)
+		do_volt_notify_handling(emif, volt_state);
+	do_freq_update();
+
+	spin_unlock_irqrestore(&emif_lock, irq_state);
+}
+
+static void do_freq_pre_notify_handling(struct emif_data *emif, u32 new_freq)
+{
+	struct emif_regs *regs;
+
+	regs = get_regs(emif, new_freq);
+	if (!regs)
+		return;
+
+	emif->curr_regs = regs;
+
+	/*
+	 * Update the shadow registers:
+	 * Temperature and voltage-ramp sensitive settings are also configured
+	 * in terms of DDR cycles. So, we need to update them too when there
+	 * is a freq change
+	 */
+	dev_dbg(emif->dev, "%s: setting up shadow registers for %uHz",
+		__func__, new_freq);
+	setup_registers(emif, regs);
+	setup_temperature_sensitive_regs(emif, regs);
+	setup_volt_sensitive_regs(emif, regs, DDR_VOLTAGE_STABLE);
+
+	/*
+	 * Part of workaround for errata i728. See do_freq_update()
+	 * for more details
+	 */
+	if (emif->lpmode == EMIF_LP_MODE_SELF_REFRESH)
+		set_lpmode(emif, EMIF_LP_MODE_DISABLE);
+}
+
+/*
+ * TODO: frequency notify handling should be hooked up to
+ * clock framework as soon as the necessary support is
+ * available in mainline kernel. This function is un-used
+ * right now.
+ */
+static void __attribute__((unused)) freq_pre_notify_handling(u32 new_freq)
+{
+	struct emif_data *emif;
+
+	/*
+	 * NOTE: we are taking the spin-lock here and releases it
+	 * only in post-notifier. This doesn't look good and
+	 * Sparse complains about it, but this seems to be
+	 * un-avoidable. We need to lock a sequence of events
+	 * that is split between EMIF and clock framework.
+	 *
+	 * 1. EMIF driver updates EMIF timings in shadow registers in the
+	 *    frequency pre-notify callback from clock framework
+	 * 2. clock framework sets up the registers for the new frequency
+	 * 3. clock framework initiates a hw-sequence that updates
+	 *    the frequency EMIF timings synchronously.
+	 *
+	 * All these 3 steps should be performed as an atomic operation
+	 * vis-a-vis similar sequence in the EMIF interrupt handler
+	 * for temperature events. Otherwise, there could be race
+	 * conditions that could result in incorrect EMIF timings for
+	 * a given frequency
+	 */
+	spin_lock_irqsave(&emif_lock, irq_state);
+
+	list_for_each_entry(emif, &device_list, node)
+		do_freq_pre_notify_handling(emif, new_freq);
+}
+
+static void do_freq_post_notify_handling(struct emif_data *emif)
+{
+	/*
+	 * Part of workaround for errata i728. See do_freq_update()
+	 * for more details
+	 */
+	if (emif->lpmode == EMIF_LP_MODE_SELF_REFRESH)
+		set_lpmode(emif, EMIF_LP_MODE_SELF_REFRESH);
+}
+
+/*
+ * TODO: frequency notify handling should be hooked up to
+ * clock framework as soon as the necessary support is
+ * available in mainline kernel. This function is un-used
+ * right now.
+ */
+static void __attribute__((unused)) freq_post_notify_handling(void)
+{
+	struct emif_data *emif;
+
+	list_for_each_entry(emif, &device_list, node)
+		do_freq_post_notify_handling(emif);
+
+	/*
+	 * Lock is done in pre-notify handler. See freq_pre_notify_handling()
+	 * for more details
+	 */
+	spin_unlock_irqrestore(&emif_lock, irq_state);
+}
+
 static struct platform_driver emif_driver = {
 	.driver = {
 		.name = "emif",