59 lines
1.7 KiB
Diff
59 lines
1.7 KiB
Diff
Implement the SPI-GPIO delay function for busses that need speed limitation.
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--mb
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--- a/drivers/spi/spi-gpio.c
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+++ b/drivers/spi/spi-gpio.c
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@@ -22,6 +22,7 @@
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#include <linux/init.h>
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#include <linux/platform_device.h>
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#include <linux/gpio.h>
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+#include <linux/delay.h>
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#include <linux/of_device.h>
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#include <linux/of_gpio.h>
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@@ -73,6 +74,7 @@ struct spi_gpio {
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* #define SPI_MOSI_GPIO 120
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* #define SPI_SCK_GPIO 121
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* #define SPI_N_CHIPSEL 4
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+ * #undef NEED_SPIDELAY
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* #include "spi-gpio.c"
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*/
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@@ -80,6 +82,7 @@ struct spi_gpio {
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#define DRIVER_NAME "spi_gpio"
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#define GENERIC_BITBANG /* vs tight inlines */
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+#define NEED_SPIDELAY 1
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/* all functions referencing these symbols must define pdata */
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#define SPI_MISO_GPIO ((pdata)->miso)
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@@ -130,12 +133,20 @@ static inline int getmiso(const struct s
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#undef pdata
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/*
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- * NOTE: this clocks "as fast as we can". It "should" be a function of the
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- * requested device clock. Software overhead means we usually have trouble
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- * reaching even one Mbit/sec (except when we can inline bitops), so for now
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- * we'll just assume we never need additional per-bit slowdowns.
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+ * NOTE: to clock "as fast as we can", set spi_device.max_speed_hz
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+ * and spi_transfer.speed_hz to 0.
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+ * Otherwise this is a function of the requested device clock.
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+ * Software overhead means we usually have trouble
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+ * reaching even one Mbit/sec (except when we can inline bitops). So on small
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+ * embedded devices with fast SPI slaves you usually don't need a delay.
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*/
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-#define spidelay(nsecs) do {} while (0)
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+static inline void spidelay(unsigned nsecs)
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+{
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+#ifdef NEED_SPIDELAY
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+ if (unlikely(nsecs))
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+ ndelay(nsecs);
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+#endif /* NEED_SPIDELAY */
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+}
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#include "spi-bitbang-txrx.h"
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