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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 23A50C433F5 for ; Wed, 23 Feb 2022 17:43:14 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 25AA010E120; Wed, 23 Feb 2022 17:43:13 +0000 (UTC) Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id A9D5F10E120 for ; Wed, 23 Feb 2022 17:43:12 +0000 (UTC) Received: from pendragon.ideasonboard.com (cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net [86.31.172.11]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 33DE3DD; Wed, 23 Feb 2022 18:43:11 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1645638191; bh=47L9rxSyL6sMeP7/r/hGoVdtSeR0EhBL3DwP31dkkNs=; h=In-Reply-To:References:Subject:From:Cc:To:Date:From; b=rTD0kQx7mIS3LBAJI51MgGMtGT9wVD5oCCxX5aQhrzIjhxsce6J5eSqzgVBa73eJl GxC3swsShYwedjDYQD/YYoKBKJI771U4hHrqLfo2SbMkdDFZ7/sZf4YAww9rog0lUr l3TjNqfqMlTRhJliCanz3q0DPAipeXZJqqav97Y4= Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: References: <20210322030128.2283-1-laurent.pinchart+renesas@ideasonboard.com> <20210322030128.2283-12-laurent.pinchart+renesas@ideasonboard.com> Subject: Re: [RFC PATCH 11/11] drm/bridge: ti-sn65dsi86: Support hotplug detection From: Kieran Bingham To: Doug Anderson , Laurent Pinchart Date: Wed, 23 Feb 2022 17:43:09 +0000 Message-ID: <164563818901.4066078.3221991328451321918@Monstersaurus> User-Agent: alot/0.10 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jernej Skrabec , Neil Armstrong , Jonas Karlman , dri-devel , Stephen Boyd , linux-renesas-soc@vger.kernel.org, Andrzej Hajda Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi All, I'm working to respin the remainder of these patches, now that I have IRQ based HPD working on the SN65DSI86, and the (non-eDP) mode is used for Renesas R-Car boards. Quoting Doug Anderson (2021-06-24 00:51:12) > Hi, >=20 > On Wed, Jun 23, 2021 at 4:26 PM Laurent Pinchart > wrote: > > > > > > @@ -1365,7 +1384,8 @@ static int ti_sn_bridge_probe(struct i2c_clie= nt *client, > > > > > > > > pdata->bridge.funcs =3D &ti_sn_bridge_funcs; > > > > pdata->bridge.of_node =3D client->dev.of_node; > > > > - pdata->bridge.ops =3D DRM_BRIDGE_OP_EDID; > > > > + pdata->bridge.ops =3D (pdata->no_hpd ? 0 : DRM_BRIDGE_OP_DE= TECT) > > > > > > Checking for "no_hpd" here is not the right test IIUC. You want to > > > check for eDP vs. DP (AKA whether a panel is downstream of you or a > > > connector). Specifically if downstream of you is a panel then (I > > > believe) HPD won't assert until you turn on the panel and you won't > > > turn on the panel (which happens in pre_enable, right?) until HPD > > > fires, so you've got a chicken-and-egg problem. If downstream of you > > > is a connector, though, then by definition HPD has to just work > > > without pre_enable running so then you're OK. > > > > Agreed. It's even more true now that your rework has landed, as in the > > eDP case EDID is handled by the panel driver. I'll rework this. > > > > Should I also condition setting HPD_DISABLE to the presence of a panel > > then ? I could drop of_property_read_bool() and set > > > > pdata->no_hpd =3D !!panel; > > > > > I guess then you'd need to figure out what to do if someone wants to > > > use "HPD" on eDP. Do you need to put a polling loop in pre_enable > > > then? Or you could just punt not support this case until someone needs > > > it. > > > > I think I'll stop short of saving the world this time, yes :-) We'll see > > what to do when this case arises. >=20 > How about as a compromise you still call of_property_read_bool() but > add some type of warning in the logs if someone didn't set "no-hpd" > but they have a panel? Would a mix of the two work well? What about: pdata->no_hpd =3D of_property_read_bool(np, "no-hpd"); if (panel && !pdata->no_hpd) { DRM_ERROR("Panels will not function with HPD. Enforcing no-hpd\n"); pdata->no_hpd =3D true; } That leaves it still optional to DP connectors, but enforced on eDP? > > > > + | DRM_BRIDGE_OP_EDID; > > > > > > IMO somewhere in here if HPD is being used like this you should throw > > > in a call to pm_runtime_get_sync(). I guess in your solution the > > > regulators (for the bridge, not the panel) and enable pin are just > > > left on all the time, > > > > Correct, on my development board the SN65DSI86 is on all the time, I > > can't control that. > > > > > but plausibly someone might want to build a > > > system to use HPD and also have the enable pin and/or regulators > > > controlled by this driver, right? > > > > True. DRM doesn't make this very easy, as, as far as I can tell, there's > > no standard infrastructure for userspace to register an interest in HPD > > that could be notified to bridges. I think it should be fixable, but > > it's out of scope for this series :-) Should I still add a > > pm_runtime_get_sync() at probe time, or leave this to be addressed by > > someone who will need to implement power control ? >=20 > IMO if you've detected you're running in DP mode you should add the > pm_runtime_get_sync() in probe to keep it powered all the time and > that seems the simplest. Technically I guess that's not really > required since you're polling and you could power off between polls, > but then you'd have to re-init a bunch of your state each time you > polled too. If you ever transitioned to using an IRQ for HPD then > you'd have to keep it always powered anyway. Hrm ... that's precisely what I've done. It's not IRQ based HPD... So would you like to see something like this during ti_sn_bridge_probe()? /* The device must remain powered up for HPD to be supported. */ if (!pdata->no_hpd) pm_runtime_get_sync(pdata->dev); -- Regards Kieran >=20 > -Doug