From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
Allow the cs-gpios property in DT to be used instead of the
fixed two chip-selects provided by the SPI-HW itself
Signed-off-by: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
---
There is the question if we still need to support the chip_selects
provided by the hardware (plus the buggy CSPOL_HIGH support for those cases)
or if we could just make the cs-gpios a required setting for this driver.
Going with the GPIO only solution would clean up the code a bit.
drivers/spi/spi-bcm2835.c | 53 +++++++++++++++++++++++++++++++++++++++------
1 file changed, 46 insertions(+), 7 deletions(-)
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 419a782..128a152 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -3,6 +3,7 @@
*
* Copyright (C) 2012 Chris Boot
* Copyright (C) 2013 Stephen Warren
+ * Copyright (C) 2015 Martin Sperl
*
* This driver is inspired by:
* spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@xxxxxxxxxxx>
@@ -30,6 +31,7 @@
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_device.h>
+#include <linux/of_gpio.h>
#include <linux/spi/spi.h>
/* SPI register offsets */
@@ -116,6 +118,18 @@ static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len)
}
}
+/* ideally spi_set_cs would be exported by spi-core */
+static inline void bcm2835_set_cs(struct spi_device *spi, bool enable)
+{
+
+ if (spi->mode & SPI_CS_HIGH)
+ enable = !enable;
+
+ if (spi->cs_gpio >= 0)
+ gpio_set_value(spi->cs_gpio, !enable);
+
+}
+
static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
{
struct spi_master *master = dev_id;
@@ -205,12 +219,24 @@ static int bcm2835_spi_start_transfer(struct spi_device *spi,
cs |= BCM2835_SPI_CS_CPHA;
if (!(spi->mode & SPI_NO_CS)) {
- if (spi->mode & SPI_CS_HIGH) {
- cs |= BCM2835_SPI_CS_CSPOL;
- cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select;
- }
+ if (spi->cs_gpio >= 0)
+ bcm2835_set_cs(spi, 1);
+ else {
+ /* do we need to support this ?
+ * note that there is a bug in this when there are
+ * multiple devices on the bus with at least one
+ * having SPI_CS_HIGH set (the other CS_CSPOLX get
+ * reset to 0 when any other device
+ * starts a transfer
+ */
+ if (spi->mode & SPI_CS_HIGH) {
+ cs |= BCM2835_SPI_CS_CSPOL;
+ cs |= BCM2835_SPI_CS_CSPOL0
+ << spi->chip_select;
+ }
- cs |= spi->chip_select;
+ cs |= spi->chip_select;
+ }
}
reinit_completion(&bs->done);
@@ -245,9 +271,12 @@ static int bcm2835_spi_finish_transfer(struct spi_device *spi,
if (tfr->delay_usecs)
udelay(tfr->delay_usecs);
- if (cs_change)
+ if (cs_change) {
+ /* reset CS */
+ bcm2835_set_cs(spi, 0);
/* Clear TA flag */
bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA);
+ }
return 0;
}
@@ -285,15 +314,24 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
}
out:
- /* Clear FIFOs, and disable the HW block */
+ /* Clear FIFOs, reset CS and disable the HW block */
bcm2835_wr(bs, BCM2835_SPI_CS,
BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
+ bcm2835_set_cs(spi, 0);
mesg->status = err;
spi_finalize_current_message(master);
return 0;
}
+static int bcm2835_spi_setup(struct spi_device *spi)
+{
+ /* setting up CS right from the start */
+ bcm2835_set_cs(spi, 0);
+
+ return 0;
+}
+
static int bcm2835_spi_probe(struct platform_device *pdev)
{
struct spi_master *master;
@@ -313,6 +351,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
master->bits_per_word_mask = SPI_BPW_MASK(8);
master->num_chipselect = 3;
master->transfer_one_message = bcm2835_spi_transfer_one;
+ master->setup = bcm2835_spi_setup;
master->dev.of_node = pdev->dev.of_node;
bs = spi_master_get_devdata(master);
--
1.7.10.4
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