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spi: bcm2835: reduce the abuse of the GPIO API

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Currently the bcm2835 SPI driver uses functions that are available
exclusively to GPIO providers as a way to handle a platform quirk. Let's
use a slightly better alternative that avoids poking around in GPIOLIB's
internals and use GPIO lookup tables.

Link: https://www.spinics.net/lists/linux-gpio/msg36218.html
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230911161553.24313-1-brgl@bgdev.pl
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Bartosz Golaszewski 2023-09-11 18:15:53 +02:00 committed by Mark Brown
parent 9386c958be
commit 21f252cd29
No known key found for this signature in database
GPG key ID: 24D68B725D5487D0
1 changed files with 36 additions and 26 deletions
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62
drivers/spi/spi-bcm2835.c
View file

@ -11,6 +11,7 @@
* spi-atmel.c, Copyright (C) 2006 Atmel Corporation
*/
#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/debugfs.h>
@ -26,9 +27,10 @@
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/machine.h> /* FIXME: using chip internals */
#include <linux/gpio/driver.h> /* FIXME: using chip internals */
#include <linux/gpio/machine.h> /* FIXME: using GPIO lookup tables */
#include <linux/of_irq.h>
#include <linux/overflow.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
/* SPI register offsets */
@ -83,6 +85,7 @@ MODULE_PARM_DESC(polling_limit_us,
* struct bcm2835_spi - BCM2835 SPI controller
* @regs: base address of register map
* @clk: core clock, divided to calculate serial clock
* @cs_gpio: chip-select GPIO descriptor
* @clk_hz: core clock cached speed
* @irq: interrupt, signals TX FIFO empty or RX FIFO ¾ full
* @tfr: SPI transfer currently processed
@ -117,6 +120,7 @@ MODULE_PARM_DESC(polling_limit_us,
struct bcm2835_spi {
void __iomem *regs;
struct clk *clk;
struct gpio_desc *cs_gpio;
unsigned long clk_hz;
int irq;
struct spi_transfer *tfr;
@ -1156,15 +1160,11 @@ static void bcm2835_spi_handle_err(struct spi_controller *ctlr,
bcm2835_spi_reset_hw(bs);
}
static int chip_match_name(struct gpio_chip *chip, void *data)
{
return !strcmp(chip->label, data);
}
static void bcm2835_spi_cleanup(struct spi_device *spi)
{
struct bcm2835_spidev *target = spi_get_ctldata(spi);
struct spi_controller *ctlr = spi->controller;
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
if (target->clear_rx_desc)
dmaengine_desc_free(target->clear_rx_desc);
@ -1175,6 +1175,9 @@ static void bcm2835_spi_cleanup(struct spi_device *spi)
sizeof(u32),
DMA_TO_DEVICE);
gpiod_put(bs->cs_gpio);
spi_set_csgpiod(spi, 0, NULL);
kfree(target);
}
@ -1221,7 +1224,7 @@ static int bcm2835_spi_setup(struct spi_device *spi)
struct spi_controller *ctlr = spi->controller;
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
struct bcm2835_spidev *target = spi_get_ctldata(spi);
struct gpio_chip *chip;
struct gpiod_lookup_table *lookup __free(kfree) = NULL;
int ret;
u32 cs;
@ -1288,29 +1291,36 @@ static int bcm2835_spi_setup(struct spi_device *spi)
}
/*
* Translate native CS to GPIO
* TODO: The code below is a slightly better alternative to the utter
* abuse of the GPIO API that I found here before. It creates a
* temporary lookup table, assigns it to the SPI device, gets the GPIO
* descriptor and then releases the lookup table.
*
* FIXME: poking around in the gpiolib internals like this is
* not very good practice. Find a way to locate the real problem
* and fix it. Why is the GPIO descriptor in spi->cs_gpiod
* sometimes not assigned correctly? Erroneous device trees?
* More on the problem that it addresses:
* https://www.spinics.net/lists/linux-gpio/msg36218.html
*/
/* get the gpio chip for the base */
chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
if (!chip)
return 0;
spi_set_csgpiod(spi, 0, gpiochip_request_own_desc(chip,
8 - (spi_get_chipselect(spi, 0)),
DRV_NAME,
GPIO_LOOKUP_FLAGS_DEFAULT,
GPIOD_OUT_LOW));
if (IS_ERR(spi_get_csgpiod(spi, 0))) {
ret = PTR_ERR(spi_get_csgpiod(spi, 0));
lookup = kzalloc(struct_size(lookup, table, 1), GFP_KERNEL);
if (!lookup) {
ret = -ENOMEM;
goto err_cleanup;
}
lookup->dev_id = dev_name(&spi->dev);
lookup->table[0] = GPIO_LOOKUP("pinctrl-bcm2835",
8 - (spi_get_chipselect(spi, 0)),
"cs", GPIO_LOOKUP_FLAGS_DEFAULT);
gpiod_add_lookup_table(lookup);
bs->cs_gpio = gpiod_get(&spi->dev, "cs", GPIOD_OUT_LOW);
gpiod_remove_lookup_table(lookup);
if (IS_ERR(bs->cs_gpio)) {
ret = PTR_ERR(bs->cs_gpio);
goto err_cleanup;
}
spi_set_csgpiod(spi, 0, bs->cs_gpio);
/* and set up the "mode" and level */
dev_info(&spi->dev, "setting up native-CS%i to use GPIO\n",
spi_get_chipselect(spi, 0));