diff options
| -rw-r--r-- | Documentation/spi/pxa2xx | 34 | ||||
| -rw-r--r-- | drivers/spi/pxa2xx_spi.c | 46 |
2 files changed, 50 insertions, 30 deletions
diff --git a/Documentation/spi/pxa2xx b/Documentation/spi/pxa2xx index bbe8dee..6bb916d 100644 --- a/Documentation/spi/pxa2xx +++ b/Documentation/spi/pxa2xx @@ -96,7 +96,7 @@ Each slave device attached to the PXA must provide slave specific configuration information via the structure "pxa2xx_spi_chip" found in "arch/arm/mach-pxa/include/mach/pxa2xx_spi.h". The pxa2xx_spi master controller driver will uses the configuration whenever the driver communicates with the slave -device. +device. All fields are optional. struct pxa2xx_spi_chip { u8 tx_threshold; @@ -112,14 +112,17 @@ used to configure the SSP hardware fifo. These fields are critical to the performance of pxa2xx_spi driver and misconfiguration will result in rx fifo overruns (especially in PIO mode transfers). Good default values are - .tx_threshold = 12, - .rx_threshold = 4, + .tx_threshold = 8, + .rx_threshold = 8, + +The range is 1 to 16 where zero indicates "use default". The "pxa2xx_spi_chip.dma_burst_size" field is used to configure PXA2xx DMA engine and is related the "spi_device.bits_per_word" field. Read and understand the PXA2xx "Developer Manual" sections on the DMA controller and SSP Controllers to determine the correct value. An SSP configured for byte-wide transfers would -use a value of 8. +use a value of 8. The driver will determine a reasonable default if +dma_burst_size == 0. The "pxa2xx_spi_chip.timeout" fields is used to efficiently handle trailing bytes in the SSP receiver fifo. The correct value for this field is @@ -137,7 +140,13 @@ function for asserting/deasserting a slave device chip select. If the field is NULL, the pxa2xx_spi master controller driver assumes that the SSP port is configured to use SSPFRM instead. -NSSP SALVE SAMPLE +NOTE: the SPI driver cannot control the chip select if SSPFRM is used, so the +chipselect is dropped after each spi_transfer. Most devices need chip select +asserted around the complete message. Use SSPFRM as a GPIO (through cs_control) +to accomodate these chips. + + +NSSP SLAVE SAMPLE ----------------- The pxa2xx_spi_chip structure is passed to the pxa2xx_spi driver in the "spi_board_info.controller_data" field. Below is a sample configuration using @@ -206,18 +215,21 @@ static void __init streetracer_init(void) DMA and PIO I/O Support ----------------------- -The pxa2xx_spi driver support both DMA and interrupt driven PIO message -transfers. The driver defaults to PIO mode and DMA transfers must enabled by -setting the "enable_dma" flag in the "pxa2xx_spi_master" structure and -ensuring that the "pxa2xx_spi_chip.dma_burst_size" field is non-zero. The DMA -mode support both coherent and stream based DMA mappings. +The pxa2xx_spi driver supports both DMA and interrupt driven PIO message +transfers. The driver defaults to PIO mode and DMA transfers must be enabled +by setting the "enable_dma" flag in the "pxa2xx_spi_master" structure. The DMA +mode supports both coherent and stream based DMA mappings. The following logic is used to determine the type of I/O to be used on a per "spi_transfer" basis: -if !enable_dma or dma_burst_size == 0 then +if !enable_dma then always use PIO transfers +if spi_message.len > 8191 then + print "rate limited" warning + use PIO transfers + if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then use coherent DMA mode diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c index 59ae3ed..dae87b1 100644 --- a/drivers/spi/pxa2xx_spi.c +++ b/drivers/spi/pxa2xx_spi.c @@ -47,6 +47,10 @@ MODULE_ALIAS("platform:pxa2xx-spi"); #define MAX_BUSES 3 +#define RX_THRESH_DFLT 8 +#define TX_THRESH_DFLT 8 +#define TIMOUT_DFLT 1000 + #define DMA_INT_MASK (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR) #define RESET_DMA_CHANNEL (DCSR_NODESC | DMA_INT_MASK) #define IS_DMA_ALIGNED(x) ((((u32)(x)) & 0x07) == 0) @@ -1171,6 +1175,8 @@ static int setup(struct spi_device *spi) struct driver_data *drv_data = spi_master_get_devdata(spi->master); struct ssp_device *ssp = drv_data->ssp; unsigned int clk_div; + uint tx_thres = TX_THRESH_DFLT; + uint rx_thres = RX_THRESH_DFLT; if (!spi->bits_per_word) spi->bits_per_word = 8; @@ -1209,8 +1215,7 @@ static int setup(struct spi_device *spi) chip->cs_control = null_cs_control; chip->enable_dma = 0; - chip->timeout = 1000; - chip->threshold = SSCR1_RxTresh(1) | SSCR1_TxTresh(1); + chip->timeout = TIMOUT_DFLT; chip->dma_burst_size = drv_data->master_info->enable_dma ? DCMD_BURST8 : 0; } @@ -1224,22 +1229,21 @@ static int setup(struct spi_device *spi) if (chip_info) { if (chip_info->cs_control) chip->cs_control = chip_info->cs_control; - - chip->timeout = chip_info->timeout; - - chip->threshold = (SSCR1_RxTresh(chip_info->rx_threshold) & - SSCR1_RFT) | - (SSCR1_TxTresh(chip_info->tx_threshold) & - SSCR1_TFT); - - chip->enable_dma = chip_info->dma_burst_size != 0 - && drv_data->master_info->enable_dma; + if (chip_info->timeout) + chip->timeout = chip_info->timeout; + if (chip_info->tx_threshold) + tx_thres = chip_info->tx_threshold; + if (chip_info->rx_threshold) + rx_thres = chip_info->rx_threshold; + chip->enable_dma = drv_data->master_info->enable_dma; chip->dma_threshold = 0; - if (chip_info->enable_loopback) chip->cr1 = SSCR1_LBM; } + chip->threshold = (SSCR1_RxTresh(rx_thres) & SSCR1_RFT) | + (SSCR1_TxTresh(tx_thres) & SSCR1_TFT); + /* set dma burst and threshold outside of chip_info path so that if * chip_info goes away after setting chip->enable_dma, the * burst and threshold can still respond to changes in bits_per_word */ @@ -1268,17 +1272,19 @@ static int setup(struct spi_device *spi) /* NOTE: PXA25x_SSP _could_ use external clocking ... */ if (drv_data->ssp_type != PXA25x_SSP) - dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d\n", + dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d, %s\n", spi->bits_per_word, clk_get_rate(ssp->clk) / (1 + ((chip->cr0 & SSCR0_SCR) >> 8)), - spi->mode & 0x3); + spi->mode & 0x3, + chip->enable_dma ? "DMA" : "PIO"); else - dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d\n", + dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d, %s\n", spi->bits_per_word, - clk_get_rate(ssp->clk) + clk_get_rate(ssp->clk) / 2 / (1 + ((chip->cr0 & SSCR0_SCR) >> 8)), - spi->mode & 0x3); + spi->mode & 0x3, + chip->enable_dma ? "DMA" : "PIO"); if (spi->bits_per_word <= 8) { chip->n_bytes = 1; @@ -1498,7 +1504,9 @@ static int __init pxa2xx_spi_probe(struct platform_device *pdev) /* Load default SSP configuration */ write_SSCR0(0, drv_data->ioaddr); - write_SSCR1(SSCR1_RxTresh(4) | SSCR1_TxTresh(12), drv_data->ioaddr); + write_SSCR1(SSCR1_RxTresh(RX_THRESH_DFLT) | + SSCR1_TxTresh(TX_THRESH_DFLT), + drv_data->ioaddr); write_SSCR0(SSCR0_SerClkDiv(2) | SSCR0_Motorola | SSCR0_DataSize(8), |
