spi: pxa2xx_spi: introduce chipselect GPIO to simplify the common cases

Most SPI peripherals use GPIOs as their chip selects, introduce .gpio_cs
for this.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Cc: David Brownell <david-b@pacbell.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 79 insertions, 18 deletions

diff --git a/arch/arm/mach-pxa/include/mach/pxa2xx_spi.h b/arch/arm/mach-pxa/include/mach/pxa2xx_spi.h
index 2206cb61a9f9..b87cecd9bbdc 100644
--- a/arch/arm/mach-pxa/include/mach/pxa2xx_spi.h
+++ b/arch/arm/mach-pxa/include/mach/pxa2xx_spi.h
@@ -38,6 +38,7 @@ struct pxa2xx_spi_chip {
         u8 dma_burst_size;
         u32 timeout;
         u8 enable_loopback;
+        int gpio_cs;
         void (*cs_control)(u32 command);
 };
 
diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index 33fcef3150d4..70ff0072cb8a 100644
--- a/drivers/spi/pxa2xx_spi.c
+++ b/drivers/spi/pxa2xx_spi.c
@@ -28,6 +28,7 @@
 #include <linux/workqueue.h>
 #include <linux/delay.h>
 #include <linux/clk.h>
+#include <linux/gpio.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -166,6 +167,8 @@ struct chip_data {
         u8 enable_dma;
         u8 bits_per_word;
         u32 speed_hz;
+        int gpio_cs;
+        int gpio_cs_inverted;
         int (*write)(struct driver_data *drv_data);
         int (*read)(struct driver_data *drv_data);
         void (*cs_control)(u32 command);
@@ -173,6 +176,32 @@ struct chip_data {
 
 static void pump_messages(struct work_struct *work);
 
+static void cs_assert(struct driver_data *drv_data)
+{
+        struct chip_data *chip = drv_data->cur_chip;
+
+        if (chip->cs_control) {
+                chip->cs_control(PXA2XX_CS_ASSERT);
+                return;
+        }
+
+        if (gpio_is_valid(chip->gpio_cs))
+                gpio_set_value(chip->gpio_cs, chip->gpio_cs_inverted);
+}
+
+static void cs_deassert(struct driver_data *drv_data)
+{
+        struct chip_data *chip = drv_data->cur_chip;
+
+        if (chip->cs_control) {
+                chip->cs_control(PXA2XX_CS_ASSERT);
+                return;
+        }
+
+        if (gpio_is_valid(chip->gpio_cs))
+                gpio_set_value(chip->gpio_cs, !chip->gpio_cs_inverted);
+}
+
 static int flush(struct driver_data *drv_data)
 {
         unsigned long limit = loops_per_jiffy << 1;
@@ -189,10 +218,6 @@ static int flush(struct driver_data *drv_data)
         return limit;
 }
 
-static void null_cs_control(u32 command)
-{
-}
-
 static int null_writer(struct driver_data *drv_data)
 {
         void __iomem *reg = drv_data->ioaddr;
@@ -400,7 +425,6 @@ static void giveback(struct driver_data *drv_data)
         msg = drv_data->cur_msg;
         drv_data->cur_msg = NULL;
         drv_data->cur_transfer = NULL;
-        drv_data->cur_chip = NULL;
         queue_work(drv_data->workqueue, &drv_data->pump_messages);
         spin_unlock_irqrestore(&drv_data->lock, flags);
 
@@ -416,7 +440,7 @@ static void giveback(struct driver_data *drv_data)
          * a message with an error, or next message is for another chip
          */
         if (!last_transfer->cs_change)
-                drv_data->cs_control(PXA2XX_CS_DEASSERT);
+                cs_deassert(drv_data);
         else {
                 struct spi_message *next_msg;
 
@@ -445,12 +469,14 @@ static void giveback(struct driver_data *drv_data)
                 if (next_msg && next_msg->spi != msg->spi)
                         next_msg = NULL;
                 if (!next_msg || msg->state == ERROR_STATE)
-                        drv_data->cs_control(PXA2XX_CS_DEASSERT);
+                        cs_deassert(drv_data);
         }
 
         msg->state = NULL;
         if (msg->complete)
                 msg->complete(msg->context);
+
+        drv_data->cur_chip = NULL;
 }
 
 static int wait_ssp_rx_stall(void const __iomem *ioaddr)
@@ -887,7 +913,7 @@ static void pump_transfers(unsigned long data)
 
                 /* Drop chip select only if cs_change is requested */
                 if (previous->cs_change)
-                        drv_data->cs_control(PXA2XX_CS_DEASSERT);
+                        cs_deassert(drv_data);
         }
 
         /* Check for transfers that need multiple DMA segments */
@@ -922,7 +948,6 @@ static void pump_transfers(unsigned long data)
         }
         drv_data->n_bytes = chip->n_bytes;
         drv_data->dma_width = chip->dma_width;
-        drv_data->cs_control = chip->cs_control;
         drv_data->tx = (void *)transfer->tx_buf;
         drv_data->tx_end = drv_data->tx + transfer->len;
         drv_data->rx = transfer->rx_buf;
@@ -1084,11 +1109,7 @@ static void pump_transfers(unsigned long data)
                         write_SSTO(chip->timeout, reg);
         }
 
-        /* FIXME, need to handle cs polarity,
-         * this driver uses struct pxa2xx_spi_chip.cs_control to
-         * specify a CS handling function, and it ignores most
-         * struct spi_device.mode[s], including SPI_CS_HIGH */
-        drv_data->cs_control(PXA2XX_CS_ASSERT);
+        cs_assert(drv_data);
 
         /* after chip select, release the data by enabling service
          * requests and interrupts, without changing any mode bits */
@@ -1166,6 +1187,44 @@ static int transfer(struct spi_device *spi, struct spi_message *msg)
 /* the spi->mode bits understood by this driver: */
 #define MODEBITS (SPI_CPOL | SPI_CPHA)
 
+static int setup_cs(struct spi_device *spi, struct chip_data *chip,
+                    struct pxa2xx_spi_chip *chip_info)
+{
+        int err = 0;
+
+        if (chip == NULL || chip_info == NULL)
+                return 0;
+
+        /* NOTE: setup() can be called multiple times, possibly with
+         * different chip_info, release previously requested GPIO
+         */
+        if (gpio_is_valid(chip->gpio_cs))
+                gpio_free(chip->gpio_cs);
+
+        /* If (*cs_control) is provided, ignore GPIO chip select */
+        if (chip_info->cs_control) {
+                chip->cs_control = chip_info->cs_control;
+                return 0;
+        }
+
+        if (gpio_is_valid(chip_info->gpio_cs)) {
+                err = gpio_request(chip_info->gpio_cs, "SPI_CS");
+                if (err) {
+                        dev_err(&spi->dev, "failed to request chip select "
+                                        "GPIO%d\n", chip_info->gpio_cs);
+                        return err;
+                }
+
+                chip->gpio_cs = chip_info->gpio_cs;
+                chip->gpio_cs_inverted = spi->mode & SPI_CS_HIGH;
+
+                err = gpio_direction_output(chip->gpio_cs,
+                                        !chip->gpio_cs_inverted);
+        }
+
+        return err;
+}
+
 static int setup(struct spi_device *spi)
 {
         struct pxa2xx_spi_chip *chip_info = NULL;
@@ -1211,7 +1270,7 @@ static int setup(struct spi_device *spi)
                         return -ENOMEM;
                 }
 
-                chip->cs_control = null_cs_control;
+                chip->gpio_cs = -1;
                 chip->enable_dma = 0;
                 chip->timeout = TIMOUT_DFLT;
                 chip->dma_burst_size = drv_data->master_info->enable_dma ?
@@ -1225,8 +1284,6 @@ static int setup(struct spi_device *spi)
         /* chip_info isn't always needed */
         chip->cr1 = 0;
         if (chip_info) {
-                if (chip_info->cs_control)
-                        chip->cs_control = chip_info->cs_control;
                 if (chip_info->timeout)
                         chip->timeout = chip_info->timeout;
                 if (chip_info->tx_threshold)
@@ -1308,13 +1365,16 @@ static int setup(struct spi_device *spi)
 
         spi_set_ctldata(spi, chip);
 
-        return 0;
+        return setup_cs(spi, chip, chip_info);
 }
 
 static void cleanup(struct spi_device *spi)
 {
         struct chip_data *chip = spi_get_ctldata(spi);
 
+        if (gpio_is_valid(chip->gpio_cs))
+                gpio_free(chip->gpio_cs);
+
         kfree(chip);
 }