X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=Documentation%2Fspi%2Fpxa2xx;h=6bb916d57c957754fd9b4915c4d1a42e3a4cc8ac;hb=44a504c405ae5c3a80e71acf71d6b1cb0db70715;hp=f9717fe9bd85296c8ae892003f70f013262a5fb1;hpb=741441ab7800f1eb031e74fd720f4f8f361678ed;p=linux-2.6-omap-h63xx.git

diff --git a/Documentation/spi/pxa2xx b/Documentation/spi/pxa2xx
index f9717fe9bd8..6bb916d57c9 100644
--- a/Documentation/spi/pxa2xx
+++ b/Documentation/spi/pxa2xx
@@ -1,4 +1,4 @@
-PXA2xx SPI on SSP driver HOWTO
+PXA2xx SPI on SSP driver HOWTO
 ===================================================
 This a mini howto on the pxa2xx_spi driver.  The driver turns a PXA2xx
 synchronous serial port into a SPI master controller
@@ -19,7 +19,7 @@ Declaring PXA2xx Master Controllers
 -----------------------------------
 Typically a SPI master is defined in the arch/.../mach-*/board-*.c as a
 "platform device".  The master configuration is passed to the driver via a table
-found in include/asm-arm/arch-pxa/pxa2xx_spi.h:
+found in arch/arm/mach-pxa/include/mach/pxa2xx_spi.h:
 
 struct pxa2xx_spi_master {
 	enum pxa_ssp_type ssp_type;
@@ -62,7 +62,7 @@ static struct resource pxa_spi_nssp_resources[] = {
 
 static struct pxa2xx_spi_master pxa_nssp_master_info = {
 	.ssp_type = PXA25x_NSSP, /* Type of SSP */
-	.clock_enable = CKEN9_NSSP, /* NSSP Peripheral clock */
+	.clock_enable = CKEN_NSSP, /* NSSP Peripheral clock */
 	.num_chipselect = 1, /* Matches the number of chips attached to NSSP */
 	.enable_dma = 1, /* Enables NSSP DMA */
 };
@@ -94,9 +94,9 @@ using the "spi_board_info" structure found in "linux/spi/spi.h". See
 
 Each slave device attached to the PXA must provide slave specific configuration
 information via the structure "pxa2xx_spi_chip" found in
-"include/asm-arm/arch-pxa/pxa2xx_spi.h".  The pxa2xx_spi master controller driver
+"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