OMAP4: PRM: add module hard reset support

Most processor modules (e.g., DSP, IVA, IPU) on OMAPs can be reset
under the control of the PRM.  This patch adds an API for this purpose
for OMAP4 devices:

int omap4_prm_is_hardreset_asserted(void __iomem *rstctrl_reg, u8 shift);
int omap4_prm_assert_hardreset(void __iomem *rstctrl_reg, u8 shift);
int omap4_prm_deassert_hardreset(void __iomem *rstctrl_reg, u8 shift);

This API is intended to be used only by the hwmod code - a subsequent
patch will add that support to hwmod.

This patch is a collaboration between Benoît Cousson <b-cousson@ti.com>
and Paul Walmsley <paul@pwsan.com>.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Benoît Cousson <b-cousson@ti.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/arch/arm/mach-omap2/prm44xx.c b/arch/arm/mach-omap2/prm44xx.c
new file mode 100644
index 0000000..a1ff918
--- /dev/null
+++ b/arch/arm/mach-omap2/prm44xx.c
@@ -0,0 +1,116 @@
+/*
+ * OMAP4 PRM module functions
+ *
+ * Copyright (C) 2010 Texas Instruments, Inc.
+ * Copyright (C) 2010 Nokia Corporation
+ * Benoît Cousson
+ * Paul Walmsley
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+
+#include <plat/common.h>
+#include <plat/cpu.h>
+#include <plat/prcm.h>
+
+#include "prm.h"
+#include "prm-regbits-44xx.h"
+
+/*
+ * Address offset (in bytes) between the reset control and the reset
+ * status registers: 4 bytes on OMAP4
+ */
+#define OMAP4_RST_CTRL_ST_OFFSET		4
+
+/**
+ * omap4_prm_is_hardreset_asserted - read the HW reset line state of
+ * submodules contained in the hwmod module
+ * @rstctrl_reg: RM_RSTCTRL register address for this module
+ * @shift: register bit shift corresponding to the reset line to check
+ *
+ * Returns 1 if the (sub)module hardreset line is currently asserted,
+ * 0 if the (sub)module hardreset line is not currently asserted, or
+ * -EINVAL upon parameter error.
+ */
+int omap4_prm_is_hardreset_asserted(void __iomem *rstctrl_reg, u8 shift)
+{
+	if (!cpu_is_omap44xx() || !rstctrl_reg)
+		return -EINVAL;
+
+	return omap4_prm_read_bits_shift(rstctrl_reg, (1 << shift));
+}
+
+/**
+ * omap4_prm_assert_hardreset - assert the HW reset line of a submodule
+ * @rstctrl_reg: RM_RSTCTRL register address for this module
+ * @shift: register bit shift corresponding to the reset line to assert
+ *
+ * Some IPs like dsp, ipu or iva contain processors that require an HW
+ * reset line to be asserted / deasserted in order to fully enable the
+ * IP.  These modules may have multiple hard-reset lines that reset
+ * different 'submodules' inside the IP block.  This function will
+ * place the submodule into reset.  Returns 0 upon success or -EINVAL
+ * upon an argument error.
+ */
+int omap4_prm_assert_hardreset(void __iomem *rstctrl_reg, u8 shift)
+{
+	u32 mask;
+
+	if (!cpu_is_omap44xx() || !rstctrl_reg)
+		return -EINVAL;
+
+	mask = 1 << shift;
+	omap4_prm_rmw_reg_bits(mask, mask, rstctrl_reg);
+
+	return 0;
+}
+
+/**
+ * omap4_prm_deassert_hardreset - deassert a submodule hardreset line and wait
+ * @rstctrl_reg: RM_RSTCTRL register address for this module
+ * @shift: register bit shift corresponding to the reset line to deassert
+ *
+ * Some IPs like dsp, ipu or iva contain processors that require an HW
+ * reset line to be asserted / deasserted in order to fully enable the
+ * IP.  These modules may have multiple hard-reset lines that reset
+ * different 'submodules' inside the IP block.  This function will
+ * take the submodule out of reset and wait until the PRCM indicates
+ * that the reset has completed before returning.  Returns 0 upon success or
+ * -EINVAL upon an argument error, -EEXIST if the submodule was already out
+ * of reset, or -EBUSY if the submodule did not exit reset promptly.
+ */
+int omap4_prm_deassert_hardreset(void __iomem *rstctrl_reg, u8 shift)
+{
+	u32 mask;
+	void __iomem *rstst_reg;
+	int c;
+
+	if (!cpu_is_omap44xx() || !rstctrl_reg)
+		return -EINVAL;
+
+	rstst_reg = rstctrl_reg + OMAP4_RST_CTRL_ST_OFFSET;
+
+	mask = 1 << shift;
+
+	/* Check the current status to avoid de-asserting the line twice */
+	if (omap4_prm_read_bits_shift(rstctrl_reg, mask) == 0)
+		return -EEXIST;
+
+	/* Clear the reset status by writing 1 to the status bit */
+	omap4_prm_rmw_reg_bits(0xffffffff, mask, rstst_reg);
+	/* de-assert the reset control line */
+	omap4_prm_rmw_reg_bits(mask, 0, rstctrl_reg);
+	/* wait the status to be set */
+	omap_test_timeout(omap4_prm_read_bits_shift(rstst_reg, mask),
+			  MAX_MODULE_HARDRESET_WAIT, c);
+
+	return (c == MAX_MODULE_HARDRESET_WAIT) ? -EBUSY : 0;
+}
+