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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD2C1C433F5 for ; Fri, 4 Mar 2022 18:34:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241703AbiCDSfD convert rfc822-to-8bit (ORCPT ); Fri, 4 Mar 2022 13:35:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235729AbiCDSfA (ORCPT ); Fri, 4 Mar 2022 13:35:00 -0500 Received: from aposti.net (aposti.net [89.234.176.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A2A55F66; Fri, 4 Mar 2022 10:34:12 -0800 (PST) Date: Fri, 04 Mar 2022 18:33:59 +0000 From: Paul Cercueil Subject: Re: [Letux-kernel] [PATCH v16 1/4] drm/bridge: dw-hdmi: introduce dw_hdmi_enable_poll() To: "H. Nikolaus Schaller" Cc: Neil Armstrong , Paul Boddie , Andrzej Hajda , Maxime Ripard , Jonas Karlman , David Airlie , Robert Foss , linux-mips , dri-devel , linux-kernel , Kieran Bingham , Jernej Skrabec , Discussions about the Letux Kernel , Laurent Pinchart Message-Id: In-Reply-To: <5CC8B441-AA50-45F5-A5D3-2F40F72A1B50@goldelico.com> References: <983e9064-17ad-e646-f37d-ca9173ba0967@baylibre.com> <3E620AF4-402E-45EA-9D92-92EAEA9647F5@goldelico.com> <929BF693-D54F-40F0-BB61-520301D1C31F@goldelico.com> <8JF88R.9V5YQ3Q6E8QO2@crapouillou.net> <5CC8B441-AA50-45F5-A5D3-2F40F72A1B50@goldelico.com> 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-kernel@vger.kernel.org Le ven., mars 4 2022 at 19:15:13 +0100, H. Nikolaus Schaller a écrit : > Hi Paul, > >> Am 04.03.2022 um 19:04 schrieb Paul Cercueil : >> >> >> >> Le ven., mars 4 2022 at 18:51:14 +0100, H. Nikolaus Schaller >> a écrit : >>> Hi Paul, Neil, >>>> Am 04.03.2022 um 17:47 schrieb Paul Cercueil >>>> : >>>> From what I understood in Nikolaus' last message, HDMI hotplug is >>>> actually correctly detected, so there's no need for polling. What >>>> is missing is the call to drm_kms_helper_hotplug_event >>>> *somewhere*, so that the information is correctly relayed to >>>> userspace. >>> Exactly. >>> As Maxime pointed out it should already be called by >>> drm_helper_hpd_irq_event() in dw_hdmi_irq() but isn't >>> because mode_config.poll_enabled isn't enabled. >>> So we can either >>> a) enable mode_config.poll_enabled so that it is called by >>> drm_helper_hpd_irq_event() or >>> b) make drm_kms_helper_hotplug_event() being called explicitly in >>> dw_hdmi_irq(). >>> We could guard that by mode_config.poll_enabled to avoid >>> drm_kms_helper_hotplug_event() >>> being called twice (but I think the "changed" mechanism will >>> take care of). >>>> I think this issue can be fixed by calling >>>> drm_bridge_connector_enable_hpd() on the connector in >>>> ingenic-drm-drv.c. >>> I don't see yet how this would solve it, but it may work. >> >> dw_hdmi_irq() calls drm_bridge_hpd_notify(), which would call >> bridge->hpd_cb() if it was non-NULL. > > Ok, this is a case c). > > I vaguely remember having tried to analyse what bridge->hpd_cb is but > stopped since it is NULL... > >> >> Calling drm_bridge_connector_enable_hpd() will set the >> bridge->hpd_cb() callback to point to drm_bridge_connector_hpd_cb(), >> which itself will call drm_kms_helper_hotplug_event(). Therefore, >> all that is missing is one call to drm_bridge_connector_enable_hpd(). > > Ah, ok, I see. > >>> Anyways, this all is a missing feature (sometimes called "bug") of >>> the *dw-hdmi driver* and IMHO >>> neither of the connector nor the ingenic-drm-drv. > > Well, a little more analysis shows that > drm_bridge_connector_enable_hpd is called > in the *-drv.c for some other plaforms: > > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/imx/dcss/dcss-dev.c#L292 > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/imx/dcss/dcss-kms.c#L145 > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/omapdrm/omap_drv.c#L393 > https://elixir.bootlin.com/linux/v5.17-rc6/source/drivers/gpu/drm/msm/hdmi/hdmi.c#L317 > >>> So I think it should not be solved outside dw-hdmi. > > Hm. Can we call drm_bridge_connector_enable_hpd() from inside dw-hdmi? > > Or would this be the solution if merged? (I currently can't try code). > > https://lore.kernel.org/lkml/a7d0b013-6114-07b3-0a7b-0d17db8a3982@cogentembedded.com/T/ Looks correct to me. It has been reviewed by two people so I believe it will be merged very soon. Cheers, -Paul