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spi: bcm2835: transform native-cs to gpio-cs on first spi_setup

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Transforms the bcm-2835 native SPI-chip select to their gpio-cs equivalent.

This allows for some support of some optimizations that are not
possible due to HW-gliches on the CS line - especially filling
the FIFO before enabling SPI interrupts (by writing to CS register)
while the transfer is already in progress (See commit: e3a2be3030)

This patch also works arround some issues in bcm2835-pinctrl which does not
set the value when setting the GPIO as output - it just sets up output and
(typically) leaves the GPIO as low.  When a fix for this is merged then this
gpio_set_value can get removed from bcm2835_spi_setup.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Martin Sperl 2015-04-06 17:16:31 +00:00 committed by Mark Brown
parent e3a2be3030
commit a30a555d74
1 changed files with 44 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

49
drivers/spi/spi-bcm2835.c
View file

@ -291,8 +291,15 @@ static void bcm2835_spi_set_cs(struct spi_device *spi, bool gpio_level)
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
}
static int chip_match_name(struct gpio_chip *chip, void *data)
{
return !strcmp(chip->label, data);
}
static int bcm2835_spi_setup(struct spi_device *spi)
{
int err;
struct gpio_chip *chip;
/*
* sanity checking the native-chipselects
*/
@ -300,13 +307,45 @@ static int bcm2835_spi_setup(struct spi_device *spi)
return 0;
if (gpio_is_valid(spi->cs_gpio))
return 0;
if (spi->chip_select < 3)
if (spi->chip_select > 1) {
/* error in the case of native CS requested with CS > 1
* officially there is a CS2, but it is not documented
* which GPIO is connected with that...
*/
dev_err(&spi->dev,
"setup: only two native chip-selects are supported\n");
return -EINVAL;
}
/* now translate native cs to GPIO */
/* get the gpio chip for the base */
chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
if (!chip)
return 0;
/* error in the case of native CS requested with CS-id > 2 */
dev_err(&spi->dev,
"setup: only three native chip-selects are supported\n");
return -EINVAL;
/* and calculate the real CS */
spi->cs_gpio = chip->base + 8 - spi->chip_select;
/* and set up the "mode" and level */
dev_info(&spi->dev, "setting up native-CS%i as GPIO %i\n",
spi->chip_select, spi->cs_gpio);
/* set up GPIO as output and pull to the correct level */
err = gpio_direction_output(spi->cs_gpio,
(spi->mode & SPI_CS_HIGH) ? 0 : 1);
if (err) {
dev_err(&spi->dev,
"could not set CS%i gpio %i as output: %i",
spi->chip_select, spi->cs_gpio, err);
return err;
}
/* the implementation of pinctrl-bcm2835 currently does not
* set the GPIO value when using gpio_direction_output
* so we are setting it here explicitly
*/
gpio_set_value(spi->cs_gpio, (spi->mode & SPI_CS_HIGH) ? 0 : 1);
return 0;
}
static int bcm2835_spi_probe(struct platform_device *pdev)