[PATCH 4/5] Blackfin SPI Driver: Add GPIO controlled SPI Slave Select support

Bryan Wu
2009-02-05T10:07:21Z

From: Michael Hennerich <michael.hennerich@analog.com>

This patch adds support for GPIO controlled SPI Chip Selects.
To make use of this feature, set chip_select = 0 and add a proper
cs_gpio to your controller_data.

struct spi_board_info
.chip_select = 0

struct bfin5xx_spi_chip
.cs_gpio = GPIO_P###

There are various SPI devices that require SPI MODE_0,
and need to have the Chip Selects asserted during the entire transfer.
Consider using SPI_MODE_3 (SPI_CPHA | SPI_CPOL) if your device allows
it.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
---
arch/blackfin/include/asm/bfin5xx_spi.h | 1 +
drivers/spi/spi_bfin5xx.c | 40 ++++++++++++++++++++++++------
2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/arch/blackfin/include/asm/bfin5xx_spi.h b/arch/blackfin/include/asm/bfin5xx_spi.h
index e1bb164..da8b9ca 100644
--- a/arch/blackfin/include/asm/bfin5xx_spi.h
+++ b/arch/blackfin/include/asm/bfin5xx_spi.h
@@ -124,6 +124,7 @@ struct bfin5xx_spi_chip {
u8 bits_per_word;
u8 cs_change_per_word;
u16 cs_chg_udelay; /* Some devices require 16-bit delays */
+ u32 cs_gpio;
};

#endif /* _SPI_CHANNEL_H_ */
diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
index b6098b5..5089afe 100644
--- a/drivers/spi/spi_bfin5xx.c
+++ b/drivers/spi/spi_bfin5xx.c
@@ -114,6 +114,7 @@ struct chip_data {
u8 bits_per_word; /* 8 or 16 */
u8 cs_change_per_word;
u16 cs_chg_udelay; /* Some devices require > 255usec delay */
+ u32 cs_gpio;
void (*write) (struct driver_data *);
void (*read) (struct driver_data *);
void (*duplex) (struct driver_data *);
@@ -180,22 +181,30 @@ static int bfin_spi_flush(struct driver_data *drv_data)
/* Chip select operation functions for cs_change flag */
static void bfin_spi_cs_active(struct driver_data *drv_data, struct chip_data *chip)
{
- u16 flag = read_FLAG(drv_data);
+ if (likely(chip->chip_select_num)) {
+ u16 flag = read_FLAG(drv_data);

- flag |= chip->flag;
- flag &= ~(chip->flag << 8);
+ flag |= chip->flag;
+ flag &= ~(chip->flag << 8);

- write_FLAG(drv_data, flag);
+ write_FLAG(drv_data, flag);
+ } else {
+ gpio_set_value(chip->cs_gpio, 0);
+ }
}

static void bfin_spi_cs_deactive(struct driver_data *drv_data, struct chip_data *chip)
{
- u16 flag = read_FLAG(drv_data);
+ if (likely(chip->chip_select_num)) {
+ u16 flag = read_FLAG(drv_data);

- flag &= ~chip->flag;
- flag |= (chip->flag << 8);
+ flag &= ~chip->flag;
+ flag |= (chip->flag << 8);

- write_FLAG(drv_data, flag);
+ write_FLAG(drv_data, flag);
+ } else {
+ gpio_set_value(chip->cs_gpio, 1);
+ }

/* Move delay here for consistency */
if (chip->cs_chg_udelay)
@@ -1098,6 +1107,7 @@ static int bfin_spi_setup(struct spi_device *spi)
struct bfin5xx_spi_chip *chip_info = NULL;
struct chip_data *chip;
struct driver_data *drv_data = spi_master_get_devdata(spi->master);
+ int ret;

/* Abort device setup if requested features are not supported */
if (spi->mode & ~(SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST)) {
@@ -1143,6 +1153,7 @@ static int bfin_spi_setup(struct spi_device *spi)
chip->bits_per_word = chip_info->bits_per_word;
chip->cs_change_per_word = chip_info->cs_change_per_word;
chip->cs_chg_udelay = chip_info->cs_chg_udelay;
+ chip->cs_gpio = chip_info->cs_gpio;
}

/* translate common spi framework into our register */
@@ -1183,6 +1194,16 @@ static int bfin_spi_setup(struct spi_device *spi)
chip->flag = 1 << (spi->chip_select);
chip->chip_select_num = spi->chip_select;

+ if (chip->chip_select_num == 0) {
+ ret = gpio_request(chip->cs_gpio, spi->modalias);
+ if (ret) {
+ if (drv_data->dma_requested)
+ free_dma(drv_data->dma_channel);
+ return ret;
+ }
+ gpio_direction_output(chip->cs_gpio, 1);
+ }
+
switch (chip->bits_per_word) {
case 8:
chip->n_bytes = 1;
@@ -1248,6 +1269,9 @@ static void bfin_spi_cleanup(struct spi_device *spi)
peripheral_free(ssel[spi->master->bus_num]
[chip->chip_select_num-1]);

+ if (chip->chip_select_num == 0)
+ gpio_free(chip->cs_gpio);
+
kfree(chip);
}

--
1.5.6.3