<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - [GLK DSI] Black screen after grub - Ubuntu 18.04 - kernel latest tip 21.11.2018" href="https://bugs.freedesktop.org/show_bug.cgi?id=108826#c126">Comment # 126</a> on <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - [GLK DSI] Black screen after grub - Ubuntu 18.04 - kernel latest tip 21.11.2018" href="https://bugs.freedesktop.org/show_bug.cgi?id=108826">bug 108826</a> from <a class="email" href="mailto:markwynngarcia@outlook.com" title="Mark Wynn Garcia <markwynngarcia@outlook.com>"> Mark Wynn Garcia</a> <pre>Stani. I think I know the problem. I'm still at work so I couldn't test it. I think it's because of the call to devm_gpiod_get_index() is only done once, with the first call's value. gpio_desc = devm_gpiod_get_index(dev_priv->drm.dev, NULL, gpio_index, value ? GPIOD_OUT_LOW : GPIOD_OUT_HIGH); The look at gpiod_set_value() -> gpiod_set_value_nocheck() (<a href="https://github.com/torvalds/linux/blob/master/drivers/gpio/gpiolib.c#L3335">https://github.com/torvalds/linux/blob/master/drivers/gpio/gpiolib.c#L3335</a>). It flips the value if it's flagged as low. See also gpiod_configure_flags(). So if it happens that the initial call sets the GPIOD_OUT_LOW flag, then every subsequent calls will have the value flipped. So it can never set the GPIO to 1/true!</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>