From: Stefan Roese sr@denx.de
[ Upstream commit d99482673f950817b30caf3fcdfb31179b050ce1 ]
This patch adds a check for the GPIOs property existence, before the GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio support is added (2nd patch in this patch series) on x86 platforms using ACPI.
Here Mika's comments from 2016-08-09:
" I noticed that with v4.8-rc1 serial console of some of our Broxton systems does not work properly anymore. I'm able to see output but input does not work.
I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341 ("tty/serial/8250: use mctrl_gpio helpers").
The reason why it fails is that in ACPI we do not have names for GPIOs (except when _DSD is used) so we use the "idx" to index into _CRS GPIO resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The UART device in Broxton has following (simplified) ACPI description:
Device (URT4) { ... Name (_CRS, ResourceTemplate () { GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly, "\_SB.GPO0", 0x00, ResourceConsumer) { 0x003A } GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly, "\_SB.GPO0", 0x00, ResourceConsumer) { 0x003D } })
In this case it finds the first GPIO (0x003A which happens to be RX pin for that UART), turns it into GPIO which then breaks input for the UART device. This also breaks systems with bluetooth connected to UART (those typically have some GPIOs in their _CRS).
Any ideas how to fix this?
We cannot just drop the _CRS index lookup fallback because that would break many existing machines out there so maybe we can limit this to only DT enabled machines. Or alternatively probe if the property first exists before trying to acquire the GPIOs (using device_property_present()). "
This patch implements the fix suggested by Mika in his statement above.
Signed-off-by: Stefan Roese sr@denx.de Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Tested-by: Yegor Yefremov yegorslists@googlemail.com Cc: Mika Westerberg mika.westerberg@linux.intel.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Yegor Yefremov yegorslists@googlemail.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Giulio Benetti giulio.benetti@micronovasrl.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/serial_mctrl_gpio.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c index d2da6aa7f27d..42e42e3e7a6e 100644 --- a/drivers/tty/serial/serial_mctrl_gpio.c +++ b/drivers/tty/serial/serial_mctrl_gpio.c @@ -21,6 +21,7 @@ #include <linux/termios.h> #include <linux/serial_core.h> #include <linux/module.h> +#include <linux/property.h>
#include "serial_mctrl_gpio.h"
@@ -124,6 +125,19 @@ struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
for (i = 0; i < UART_GPIO_MAX; i++) { enum gpiod_flags flags; + char *gpio_str; + bool present; + + /* Check if GPIO property exists and continue if not */ + gpio_str = kasprintf(GFP_KERNEL, "%s-gpios", + mctrl_gpios_desc[i].name); + if (!gpio_str) + continue; + + present = device_property_present(dev, gpio_str); + kfree(gpio_str); + if (!present) + continue;
if (mctrl_gpios_desc[i].dir_out) flags = GPIOD_OUT_LOW;