summaryrefslogtreecommitdiff
path: root/Documentation/spi
diff options
context:
space:
mode:
authorIngo Molnar <mingo@elte.hu>2008-10-28 16:26:12 +0100
committerIngo Molnar <mingo@elte.hu>2008-10-28 16:26:12 +0100
commit7a9787e1eba95a166265e6a260cf30af04ef0a99 (patch)
treee730a4565e0318140d2fbd2f0415d18a339d7336 /Documentation/spi
parent41b9eb264c8407655db57b60b4457fe1b2ec9977 (diff)
parent0173a3265b228da319ceb9c1ec6a5682fd1b2d92 (diff)
Merge commit 'v2.6.28-rc2' into x86/pci-ioapic-boot-irq-quirks
Diffstat (limited to 'Documentation/spi')
-rw-r--r--Documentation/spi/Makefile11
-rw-r--r--Documentation/spi/pxa2xx38
-rw-r--r--Documentation/spi/spi-summary4
3 files changed, 38 insertions, 15 deletions
diff --git a/Documentation/spi/Makefile b/Documentation/spi/Makefile
new file mode 100644
index 000000000000..a5b03c88beae
--- /dev/null
+++ b/Documentation/spi/Makefile
@@ -0,0 +1,11 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+# List of programs to build
+hostprogs-y := spidev_test spidev_fdx
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_spidev_test.o += -I$(objtree)/usr/include
+HOSTCFLAGS_spidev_fdx.o += -I$(objtree)/usr/include
diff --git a/Documentation/spi/pxa2xx b/Documentation/spi/pxa2xx
index f3853cc37bde..6bb916d57c95 100644
--- a/Documentation/spi/pxa2xx
+++ b/Documentation/spi/pxa2xx
@@ -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;
@@ -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
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary
index 6d5f18143c50..8bae2f018d34 100644
--- a/Documentation/spi/spi-summary
+++ b/Documentation/spi/spi-summary
@@ -210,7 +210,7 @@ board should normally be set up and registered.
So for example arch/.../mach-*/board-*.c files might have code like:
- #include <asm/arch/spi.h> /* for mysoc_spi_data */
+ #include <mach/spi.h> /* for mysoc_spi_data */
/* if your mach-* infrastructure doesn't support kernels that can
* run on multiple boards, pdata wouldn't benefit from "__init".
@@ -227,7 +227,7 @@ So for example arch/.../mach-*/board-*.c files might have code like:
And SOC-specific utility code might look something like:
- #include <asm/arch/spi.h>
+ #include <mach/spi.h>
static struct platform_device spi2 = { ... };