spi-gpio: Implement spidelay for busses that need it.

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@14525 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/linux/generic-2.6/patches-2.6.28/920-04-spi-gpio-implement-spi-delay.patch

@@ -0,0 +1,60 @@
+Implement the SPI-GPIO delay function for busses that need speed limitation.
+
+--mb
+
+
+
+Index: linux-2.6.28.5/drivers/spi/spi_gpio.c
+===================================================================
+--- linux-2.6.28.5.orig/drivers/spi/spi_gpio.c	2009-02-15 18:53:47.000000000 +0100
++++ linux-2.6.28.5/drivers/spi/spi_gpio.c	2009-02-15 19:08:58.000000000 +0100
+@@ -21,6 +21,7 @@
+ #include <linux/init.h>
+ #include <linux/platform_device.h>
+ #include <linux/gpio.h>
++#include <linux/delay.h>
+ 
+ #include <linux/spi/spi.h>
+ #include <linux/spi/spi_bitbang.h>
+@@ -69,6 +70,7 @@ struct spi_gpio {
+  *		#define	SPI_MOSI_GPIO	120
+  *		#define	SPI_SCK_GPIO	121
+  *		#define	SPI_N_CHIPSEL	4
++ *		#undef NEED_SPIDELAY
+  *		#include "spi_gpio.c"
+  */
+ 
+@@ -76,6 +78,7 @@ struct spi_gpio {
+ #define DRIVER_NAME	"spi_gpio"
+ 
+ #define GENERIC_BITBANG	/* vs tight inlines */
++#define NEED_SPIDELAY	1
+ 
+ /* all functions referencing these symbols must define pdata */
+ #define SPI_MISO_GPIO	((pdata)->miso)
+@@ -120,12 +123,20 @@ static inline int getmiso(const struct s
+ #undef pdata
+ 
+ /*
+- * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
+- * requested device clock.  Software overhead means we usually have trouble
+- * reaching even one Mbit/sec (except when we can inline bitops), so for now
+- * we'll just assume we never need additional per-bit slowdowns.
++ * NOTE:  to clock "as fast as we can", set spi_device.max_speed_hz
++ * and spi_transfer.speed_hz to 0.
++ * Otherwise this is a function of the requested device clock.
++ * Software overhead means we usually have trouble
++ * reaching even one Mbit/sec (except when we can inline bitops). So on small
++ * embedded devices with fast SPI slaves you usually don't need a delay.
+  */
+-#define spidelay(nsecs)	do {} while (0)
++static inline void spidelay(unsigned nsecs)
++{
++#ifdef NEED_SPIDELAY
++	if (unlikely(nsecs))
++		ndelay(nsecs);
++#endif /* NEED_SPIDELAY */
++}
+ 
+ #define	EXPAND_BITBANG_TXRX
+ #include <linux/spi/spi_bitbang.h>