Messages in this thread | | | Subject | Re: [PATCH 1/3 v6] serial: mctrl_gpio: Check if GPIO property exisits before requesting it | From | Stefan Roese <> | Date | Fri, 14 Jun 2019 11:29:29 +0200 |
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On 14.06.19 11:04, Yegor Yefremov wrote: > On Thu, Jun 13, 2019 at 7:08 PM Andy Shevchenko > <andriy.shevchenko@linux.intel.com> wrote: >> >> On Thu, Jun 13, 2019 at 05:45:40PM +0200, Stefan Roese wrote: >>> 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. >>> >> >> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > > I cannot compile the driver without adding #include <linux/property.h> > to drivers/tty/serial/serial_mctrl_gpio.c. > > My platform is AM335X (OMAP3). I've tried the patches both against the > main repo and also tty-next. > > Other than that everything is working.
Thanks for reporting. I'll wait a bit for other review comments and tests (thanks Andy) and will then send v7 with this header included (and compile tested on OMAP3) later next week.
BTW: Could you please add a Tested-by-tag with the next version?
Thanks, Stefan
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