From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6EC932620C9 for ; Mon, 24 Mar 2025 16:40:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742834452; cv=none; b=BMN3pX50Saqs9bdimRYhcMGcH7FXfigoIWj2L0lerpFzDl8QGP8Ue5q9goMUnVkFfBMR0Hs6E+GYpktDrkXVD2ahTuHWSdiwG0xpxjqw6ecRpfA1EYSFqHbA5h1Ta13e8c9qiUnumPSSvp36orLwDOY1cjEM4iNKH7c+zdcgjcY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742834452; c=relaxed/simple; bh=C4qCR5IiDNqllMSB5IXrinpWcZEJSikRxGwqsymPnqE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uLa3+2nA7w9nvoBnNGxQzgNrxMkaczG3D+b9qfx37LyaUlOt7Fmr1paJTJkY6xGBNGKAnlPcXsaqYW77prZ0rg0jEaVRN8C6Nin7q88fyte64ieNOyGYjv2526CyC+1TzkBmb5XLWyt3/woBKztD7/LhhAUTitDG3EatvnvYwtg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=D9C5BF6x; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="D9C5BF6x" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id EA20763F; Mon, 24 Mar 2025 17:39:00 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1742834341; bh=C4qCR5IiDNqllMSB5IXrinpWcZEJSikRxGwqsymPnqE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=D9C5BF6x32gIC0BH3a7FyjNcvNNWaxWaHdq9h6zM/K2pDHxTSBQlPYJZ+2uCV6LyZ iXiSRyd7/4n17shRFmevu6xQErMWCZJVYJE0q3JlVMdf0VTt8UlnjUZNY+ycJrcW8e Dd3MDKPVPoHCiBWrH2lV6Su8f1Uop5WY3u0ArfxE= Date: Mon, 24 Mar 2025 18:40:25 +0200 From: Laurent Pinchart To: Wolfram Sang Cc: linux-renesas-soc@vger.kernel.org, Douglas Anderson , Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org Subject: Re: [PATCH v3] drm/bridge: ti-sn65dsi86: Check bridge connection failure Message-ID: <20250324164025.GK5113@pendragon.ideasonboard.com> References: <20250318155549.19625-2-wsa+renesas@sang-engineering.com> <20250318204133.GC22890@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-renesas-soc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Tue, Mar 18, 2025 at 10:00:31PM +0100, Wolfram Sang wrote: > Hi Laurent, > > > > Read out and check the ID registers, so we can bail out if I2C > > > communication does not work or if the device is unknown. > > > > What's the advantage of that, what are you trying to guard against ? > > That a random chip at address 0x2c will be used. Is that really a problem ? That would only occur with a broken DT, is it worth guarding against a development-time issue with a runtime check that will increase boot time for every user ? > > > Tested on a > > > Renesas GrayHawk board (R-Car V4M) by using a wrong I2C address and by > > > not enabling RuntimePM for the device. > > > > What do you mean by not enabling runtime PM for the device ? > > I left out pm_runtime_get() before regmap_read_bulk(). -- Regards, Laurent Pinchart