spi: mxc: fix sf probe when using mxc_spi

MXC SPI driver has a feature whereas a GPIO line can be used to force CS high
across multiple transactions. This is set up by embedding the GPIO information
in the CS value:

cs = (cs | gpio << 8)

This merge of cs and gpio data into one value breaks the sf probe command:
if the use of gpio is required, invoking "sf probe <cs>" will not work, because
the CS argument doesn't have the GPIO information in it. Instead, the user must
use "sf probe <cs | gpio << 8>". For example, if bank 2 gpio 30 is used to force
cs high on cs 0, bus 0, then instead of typing "sf probe 0" the user now must
type "sf probe 15872".

This is inconsistent with the description of the sf probe command, and forces
the user to be aware of implementaiton details.

Fix this by introducing a new board function: board_spi_cs_gpio(), which will
accept a naked CS value, and provide the driver with the relevant GPIO, if one
is necessary.

Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Eric Benard <eric@eukrea.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>

1 files changed, 25 insertions, 23 deletions

diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c
index 2d5f3850da8..026f680d80d 100644
--- a/drivers/spi/mxc_spi.c
+++ b/drivers/spi/mxc_spi.c
@@ -25,6 +25,11 @@ static unsigned long spi_bases[] = {
 	MXC_SPI_BASE_ADDRESSES
 };
 
+__weak int board_spi_cs_gpio(unsigned bus, unsigned cs)
+{
+	return -1;
+}
+
 #define OUT	MXC_GPIO_DIRECTION_OUT
 
 #define reg_read readl
@@ -371,31 +376,30 @@ void spi_init(void)
 {
 }
 
-static int decode_cs(struct mxc_spi_slave *mxcs, unsigned int cs)
+/*
+ * Some SPI devices require active chip-select over multiple
+ * transactions, we achieve this using a GPIO. Still, the SPI
+ * controller has to be configured to use one of its own chipselects.
+ * To use this feature you have to implement board_spi_cs_gpio() to assign
+ * a gpio value for each cs (-1 if cs doesn't need to use gpio).
+ * You must use some unused on this SPI controller cs between 0 and 3.
+ */
+static int setup_cs_gpio(struct mxc_spi_slave *mxcs,
+			 unsigned int bus, unsigned int cs)
 {
 	int ret;
 
-	/*
-	 * Some SPI devices require active chip-select over multiple
-	 * transactions, we achieve this using a GPIO. Still, the SPI
-	 * controller has to be configured to use one of its own chipselects.
-	 * To use this feature you have to call spi_setup_slave() with
-	 * cs = internal_cs | (gpio << 8), and you have to use some unused
-	 * on this SPI controller cs between 0 and 3.
-	 */
-	if (cs > 3) {
-		mxcs->gpio = cs >> 8;
-		cs &= 3;
-		ret = gpio_direction_output(mxcs->gpio, !(mxcs->ss_pol));
-		if (ret) {
-			printf("mxc_spi: cannot setup gpio %d\n", mxcs->gpio);
-			return -EINVAL;
-		}
-	} else {
-		mxcs->gpio = -1;
+	mxcs->gpio = board_spi_cs_gpio(bus, cs);
+	if (mxcs->gpio == -1)
+		return 0;
+
+	ret = gpio_direction_output(mxcs->gpio, !(mxcs->ss_pol));
+	if (ret) {
+		printf("mxc_spi: cannot setup gpio %d\n", mxcs->gpio);
+		return -EINVAL;
 	}
 
-	return cs;
+	return 0;
 }
 
 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
@@ -415,14 +419,12 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 
 	mxcs->ss_pol = (mode & SPI_CS_HIGH) ? 1 : 0;
 
-	ret = decode_cs(mxcs, cs);
+	ret = setup_cs_gpio(mxcs, bus, cs);
 	if (ret < 0) {
 		free(mxcs);
 		return NULL;
 	}
 
-	cs = ret;
-
 	mxcs->base = spi_bases[bus];
 
 	ret = spi_cfg_mxc(mxcs, cs, max_hz, mode);