From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DCCF8C432BE for ; Thu, 5 Aug 2021 20:05:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEC1D61154 for ; Thu, 5 Aug 2021 20:05:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239199AbhHEUFu convert rfc822-to-8bit (ORCPT ); Thu, 5 Aug 2021 16:05:50 -0400 Received: from aposti.net ([89.234.176.197]:57792 "EHLO aposti.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231184AbhHEUFu (ORCPT ); Thu, 5 Aug 2021 16:05:50 -0400 Date: Thu, 05 Aug 2021 22:05:27 +0200 From: Paul Cercueil Subject: Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers To: Greg Kroah-Hartman Cc: Rob Herring , "Rafael J . Wysocki" , David Airlie , Daniel Vetter , Sam Ravnborg , list@opendingux.net, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, dri-devel@lists.freedesktop.org Message-Id: <3HUDXQ.7RBGD4FUHR2F@crapouillou.net> In-Reply-To: References: <20210805192110.90302-1-paul@crapouillou.net> <20210805192110.90302-3-paul@crapouillou.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Hi Greg, Le jeu., août 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman a écrit : > On Thu, Aug 05, 2021 at 09:21:09PM +0200, Paul Cercueil wrote: >> When the drivers of remote devices (e.g. HDMI chip) are disabled in >> the >> config, we want the ingenic-drm driver to be able to probe >> nonetheless >> with the other devices (e.g. internal LCD panel) that are enabled. >> >> Signed-off-by: Paul Cercueil >> --- >> drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> index d261f7a03b18..5e1fdbb0ba6b 100644 >> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> @@ -1058,6 +1058,18 @@ static int ingenic_drm_bind(struct device >> *dev, bool has_components) >> for (i = 0; ; i++) { >> ret = drm_of_find_panel_or_bridge(dev->of_node, 0, i, &panel, >> &bridge); >> if (ret) { >> + /* >> + * Workaround for the case where the drivers for the >> + * remote devices are not enabled. When that happens, >> + * drm_of_find_panel_or_bridge() returns -EPROBE_DEFER >> + * endlessly, which prevents the ingenic-drm driver from >> + * working at all. >> + */ >> + if (ret == -EPROBE_DEFER) { >> + ret = driver_deferred_probe_check_state(dev); >> + if (ret == -ENODEV || ret == -ETIMEDOUT) >> + continue; >> + } > > So you are mucking around with devices on other busses within this > driver? What could go wrong? :( I'm doing the same thing as everybody else. This is the DRM driver, and there is a driver for the external HDMI chip which gives us a DRM bridge that we can obtain from the device tree. > Please use the existing driver core functionality for this type of > thing, it is not unique, no need for this function to be called. I'm not sure you understand what I'm doing here. This driver calls drm_of_find_panel_or_bridge(), without guarantee that the driver for the remote device (connected via DT graph) has been enabled in the kernel config. In that case it will always return -EPROBE_DEFER and the ingenic-drm driver will never probe. This patch makes sure that the driver can probe if the HDMI driver has been disabled in the kernel config, nothing more. Cheers, -Paul