Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933945AbdCUS6W (ORCPT ); Tue, 21 Mar 2017 14:58:22 -0400 Received: from mail-it0-f67.google.com ([209.85.214.67]:35792 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933241AbdCUS54 (ORCPT ); Tue, 21 Mar 2017 14:57:56 -0400 MIME-Version: 1.0 In-Reply-To: <20161122134123.1209-2-peter.ujfalusi@ti.com> References: <20161122134123.1209-1-peter.ujfalusi@ti.com> <20161122134123.1209-2-peter.ujfalusi@ti.com> From: Geert Uytterhoeven Date: Tue, 21 Mar 2017 19:48:49 +0100 X-Google-Sender-Auth: gJacf54myGT6S_Eh0c4GwGCoHe4 Message-ID: Subject: Re: [PATCH v4 1/2] backlight: pwm_bl: Move the checks for initial power state to a separate function To: Peter Ujfalusi , Lee Jones Cc: Thierry Reding , Tomi Valkeinen , Linux PWM List , Linux Fbdev development list , "linux-kernel@vger.kernel.org" , Philipp Zabel , Linus Walleij , "linux-gpio@vger.kernel.org" , Linux-Renesas Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3400 Lines: 87 Hi Peter, On Tue, Nov 22, 2016 at 2:41 PM, Peter Ujfalusi wrote: > Move the checks to select the initial state for the backlight to a new > function and document the checks we are doing. This is far from a simple "move"... > With the separate function it is going to be easier to fix or improve the > initial power state configuration later and it is easier to read the code. > > Signed-off-by: Peter Ujfalusi > Reviewed-by: Philipp Zabel > Reviewed-by: Thierry Reding This patch (commit 7613c922315e308a in v4.11-rc1) broke the display on r8a7740/armadillo. > @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev) > pb->enable_gpio = gpio_to_desc(data->enable_gpio); > } > > - if (pb->enable_gpio) { > - /* > - * If the driver is probed from the device tree and there is a > - * phandle link pointing to the backlight node, it is safe to > - * assume that another driver will enable the backlight at the > - * appropriate time. Therefore, if it is disabled, keep it so. > - */ > - if (node && node->phandle && > - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT && > - gpiod_get_value(pb->enable_gpio) == 0) > - initial_blank = FB_BLANK_POWERDOWN; > - else > - gpiod_direction_output(pb->enable_gpio, 1); In my case, "node" points to the "/backlight" node, but phandle is NULL. Hence before, gpiod_direction_output() was called to enable the GPIO... > - } > + /* > + * If the GPIO is configured as input, change the direction to output > + * and set the GPIO as active. > + * Do not force the GPIO to active when it was already output as it > + * could cause backlight flickering or we would enable the backlight too > + * early. Leave the decision of the initial backlight state for later. > + */ > + if (pb->enable_gpio && > + gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN) > + gpiod_direction_output(pb->enable_gpio, 1); ... while now it's no longer called, as gpiod_get_direction() returns -EINVAL. Indeed, r8a7740_pfc does not implement the .get_direction() callback, so gpiod_get_direction() always returns -EINVAL, which is never equal to GPIOF_DIR_IN. Restoring the old behavior by changing the above test to if (pb->enable_gpio && (!node || !node->phandle || gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)) fixes the display for me, but leads to a more complex expression. However, changing the test to if (pb->enable_gpio && gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT) also fixes the display, as an error is always different from GPIOF_DIR_OUT. Anyone with comments or suggestions to fix this for real? Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds