On Friday, May 09, 2014 12:09 PM, Tony Lindgren wrote: > On Friday, May 09, 2014 11:25 AM, Jingoo Han wrote: > > On Friday, May 09, 2014 10:25 AM, Lee Jones wrote: > > > > > > If the GPIO for the backlight is on an I2C chip, we currently > > > get nasty warnings like this during the boot: > > > > > > WARNING: CPU: 0 PID: 6 at drivers/gpio/gpiolib.c:2364 gpiod_set_raw_value+0x40/0x4c() > > > Modules linked in: > > > CPU: 0 PID: 6 Comm: kworker/u2:0 Not tainted 3.15.0-rc4-12393-gcde9f4e #400 > > > Workqueue: deferwq deferred_probe_work_func > > > [<c0014cbc>] (unwind_backtrace) from [<c001191c>] (show_stack+0x10/0x14) > > > [<c001191c>] (show_stack) from [<c0566ae0>] (dump_stack+0x80/0x9c) > > > [<c0566ae0>] (dump_stack) from [<c003f61c>] (warn_slowpath_common+0x68/0x8c) > > > [<c003f61c>] (warn_slowpath_common) from [<c003f65c>] (warn_slowpath_null+0x1c/0x24) > > > [<c003f65c>] (warn_slowpath_null) from [<c02f7e10>] (gpiod_set_raw_value+0x40/0x4c) > > > [<c02f7e10>] (gpiod_set_raw_value) from [<c0308fbc>] (gpio_backlight_update_status+0x4c/0x74) > > > [<c0308fbc>] (gpio_backlight_update_status) from [<c030914c>] (gpio_backlight_probe+0x168/0x254) > > > [<c030914c>] (gpio_backlight_probe) from [<c0378fa8>] (platform_drv_probe+0x18/0x48) > > > [<c0378fa8>] (platform_drv_probe) from [<c0377c40>] (driver_probe_device+0x10c/0x238) > > > [<c0377c40>] (driver_probe_device) from [<c0376330>] (bus_for_each_drv+0x44/0x8c) > > > [<c0376330>] (bus_for_each_drv) from [<c0377afc>] (device_attach+0x74/0x8c) > > > [<c0377afc>] (device_attach) from [<c03771c4>] (bus_probe_device+0x88/0xb0) > > > [<c03771c4>] (bus_probe_device) from [<c03775c8>] (deferred_probe_work_func+0x64/0x94) > > > [<c03775c8>] (deferred_probe_work_func) from [<c00572e8>] (process_one_work+0x1b4/0x4bc) > > > [<c00572e8>] (process_one_work) from [<c00579d0>] (worker_thread+0x11c/0x398) > > > [<c00579d0>] (worker_thread) from [<c005dfd8>] (kthread+0xc8/0xe4) > > > [<c005dfd8>] (kthread) from [<c000e768>] (ret_from_fork+0x14/0x2c) > > > > > > Fix this by using gpio_set_value_cansleep() as suggested in > > > drivers/gpio/gpiolib.c:2364. This is what the other backlight drivers > > > are also doing. > > > > OK, I see. > > However, gpio_backlight drive can be used by a lot of gpio drivers. > > In some cases, 'can_sleep' is 'false' and gpio_set_value_cansleep() > > is unnecessary. > > > > In my opinion, gpio_set_value_cansleep() or gpio_set_value() can be > > called selectively by 'can_sleep' value. > > > > How about the following? > > > > - gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active); > > + if (gpio_cansleep(gbl->gpio)) > > + gpio_set_value_cansleep(gbl->gpio, > > + brightness ? gbl->active : !gbl->active); > > + else > > + gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active); > > It should be always fine to use gpio_set_value_cansleep(), see your > old thread from few years ago related to another backlight driver: > > https://lkml.org/lkml/2012/12/5/343 (+cc Linus Walleij, Alexandre Courbot, Russell King) OK, I see. gpio_set_value_cansleep() calls gpiod_set_raw_value_cansleep(), and gpio_set_value() calls gpiod_set_raw_value() as below. ./drivers/gpio/gpiolib.c void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value) { might_sleep_if(extra_checks); if (!desc) return; _gpiod_set_raw_value(desc, value); } EXPORT_SYMBOL_GPL(gpiod_set_raw_value_cansleep); ./drivers/gpio/gpiolib.c void gpiod_set_raw_value(struct gpio_desc *desc, int value) { if (!desc) return; /* Should be using gpio_set_value_cansleep() */ WARN_ON(desc->chip->can_sleep); _gpiod_set_raw_value(desc, value); } EXPORT_SYMBOL_GPL(gpiod_set_raw_value); Then, the difference between gpio_set_value_cansleep() or gpio_set_value() is whether might_sleep_if(extra_checks) is called or not. So, you said that "It should be always fine to use gpio_set_value_cansleep()", right? Linus Walleij, Is there any reason to keep these two functions such as gpiod_set_raw_value_cansleep() and gpiod_set_raw_value()? Best regards, Jingoo Han -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
