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From 380c336af070edf85826abbb0057bf92a03ec466 Mon Sep 17 00:00:00 2001
From: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>
Date: Wed, 1 Mar 2023 17:57:11 +0000
Subject: [PATCH] drivers: spi: Fix spi-gpio to correctly implement
sck-idle-input
Formerly, if configured using DT, CS GPIOs were driven from spi.c
and it was possible for CS to be asserted (low) *before* starting
to drive SCK. CS GPIOs have been brought under control of this
driver in both ACPI and DT cases, with a fixup for GPIO polarity.
Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>
---
drivers/spi/spi-gpio.c | 74 +++++++++++++++++++++++++++++-------------
1 file changed, 51 insertions(+), 23 deletions(-)
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -37,6 +37,7 @@ struct spi_gpio {
struct gpio_desc *mosi;
bool sck_idle_input;
struct gpio_desc **cs_gpios;
+ bool cs_dont_invert;
};
/*----------------------------------------------------------------------*/
@@ -233,12 +234,18 @@ static void spi_gpio_chipselect(struct s
gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
}
- /* Drive chip select line, if we have one */
+ /*
+ * Drive chip select line, if we have one.
+ * SPI chip selects are normally active-low, but when
+ * cs_dont_invert is set, we assume their polarity is
+ * controlled by the GPIO, and write '1' to assert.
+ */
if (spi_gpio->cs_gpios) {
struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select];
+ int val = ((spi->mode & SPI_CS_HIGH) || spi_gpio->cs_dont_invert) ?
+ is_active : !is_active;
- /* SPI chip selects are normally active-low */
- gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
+ gpiod_set_value_cansleep(cs, val);
}
if (spi_gpio->sck_idle_input && !is_active)
@@ -254,12 +261,14 @@ static int spi_gpio_setup(struct spi_dev
/*
* The CS GPIOs have already been
* initialized from the descriptor lookup.
+ * Here we set them to the non-asserted state.
*/
if (spi_gpio->cs_gpios) {
cs = spi_gpio->cs_gpios[spi->chip_select];
if (!spi->controller_state && cs)
status = gpiod_direction_output(cs,
- !(spi->mode & SPI_CS_HIGH));
+ !((spi->mode & SPI_CS_HIGH) ||
+ spi_gpio->cs_dont_invert));
}
if (!status)
@@ -336,6 +345,38 @@ static int spi_gpio_request(struct devic
return PTR_ERR_OR_ZERO(spi_gpio->sck);
}
+/*
+ * In order to implement "sck-idle-input" (which requires SCK
+ * direction and CS level to be switched in a particular order),
+ * we need to control GPIO chip selects from within this driver.
+ */
+
+static int spi_gpio_probe_get_cs_gpios(struct device *dev,
+ struct spi_master *master,
+ bool gpio_defines_polarity)
+{
+ int i;
+ struct spi_gpio *spi_gpio = spi_master_get_devdata(master);
+
+ spi_gpio->cs_dont_invert = gpio_defines_polarity;
+ spi_gpio->cs_gpios = devm_kcalloc(dev, master->num_chipselect,
+ sizeof(*spi_gpio->cs_gpios),
+ GFP_KERNEL);
+ if (!spi_gpio->cs_gpios)
+ return -ENOMEM;
+
+ for (i = 0; i < master->num_chipselect; i++) {
+ spi_gpio->cs_gpios[i] =
+ devm_gpiod_get_index(dev, "cs", i,
+ gpio_defines_polarity ?
+ GPIOD_OUT_LOW : GPIOD_OUT_HIGH);
+ if (IS_ERR(spi_gpio->cs_gpios[i]))
+ return PTR_ERR(spi_gpio->cs_gpios[i]);
+ }
+
+ return 0;
+}
+
#ifdef CONFIG_OF
static const struct of_device_id spi_gpio_dt_ids[] = {
{ .compatible = "spi-gpio" },
@@ -346,10 +387,12 @@ MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids)
static int spi_gpio_probe_dt(struct platform_device *pdev,
struct spi_master *master)
{
- master->dev.of_node = pdev->dev.of_node;
- master->use_gpio_descriptors = true;
+ struct device *dev = &pdev->dev;
- return 0;
+ master->dev.of_node = dev->of_node;
+ master->num_chipselect = gpiod_count(dev, "cs");
+
+ return spi_gpio_probe_get_cs_gpios(dev, master, true);
}
#else
static inline int spi_gpio_probe_dt(struct platform_device *pdev,
@@ -364,8 +407,6 @@ static int spi_gpio_probe_pdata(struct p
{
struct device *dev = &pdev->dev;
struct spi_gpio_platform_data *pdata = dev_get_platdata(dev);
- struct spi_gpio *spi_gpio = spi_master_get_devdata(master);
- int i;
#ifdef GENERIC_BITBANG
if (!pdata || !pdata->num_chipselect)
@@ -377,20 +418,7 @@ static int spi_gpio_probe_pdata(struct p
*/
master->num_chipselect = pdata->num_chipselect ?: 1;
- spi_gpio->cs_gpios = devm_kcalloc(dev, master->num_chipselect,
- sizeof(*spi_gpio->cs_gpios),
- GFP_KERNEL);
- if (!spi_gpio->cs_gpios)
- return -ENOMEM;
-
- for (i = 0; i < master->num_chipselect; i++) {
- spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs", i,
- GPIOD_OUT_HIGH);
- if (IS_ERR(spi_gpio->cs_gpios[i]))
- return PTR_ERR(spi_gpio->cs_gpios[i]);
- }
-
- return 0;
+ return spi_gpio_probe_get_cs_gpios(dev, master, false);
}
static int spi_gpio_probe(struct platform_device *pdev)
|