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[209.85.219.182]) by smtp.gmail.com with ESMTPSA id 85sm4081894qke.55.2021.03.23.12.07.39 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Mar 2021 12:07:39 -0700 (PDT) Received: by mail-yb1-f182.google.com with SMTP id z1so11480676ybf.6 for ; Tue, 23 Mar 2021 12:07:39 -0700 (PDT) X-Received: by 2002:a25:69c1:: with SMTP id e184mr7553038ybc.345.1616526459117; Tue, 23 Mar 2021 12:07:39 -0700 (PDT) MIME-Version: 1.0 References: <20201102181144.3469197-1-swboyd@chromium.org> <20201102181144.3469197-4-swboyd@chromium.org> <161646947526.2972785.6883720652669260316@swboyd.mtv.corp.google.com> In-Reply-To: <161646947526.2972785.6883720652669260316@swboyd.mtv.corp.google.com> From: Doug Anderson Date: Tue, 23 Mar 2021 12:07:27 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 3/4] drm/bridge: ti-sn65dsi86: Read EDID blob over DDC To: Stephen Boyd Cc: Laurent Pinchart , Andrzej Hajda , Neil Armstrong , Sam Ravnborg , Jernej Skrabec , Jonas Karlman , LKML , dri-devel , Sean Paul Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Mon, Mar 22, 2021 at 8:17 PM Stephen Boyd wrote: > > Quoting Laurent Pinchart (2021-03-17 17:20:43) > > Hi Stephen, > > > > Reviving a bit of an old thread, for a question. > > > > On Mon, Nov 02, 2020 at 10:11:43AM -0800, Stephen Boyd wrote: > > > @@ -265,6 +267,23 @@ connector_to_ti_sn_bridge(struct drm_connector *connector) > > > static int ti_sn_bridge_connector_get_modes(struct drm_connector *connector) > > > { > > > struct ti_sn_bridge *pdata = connector_to_ti_sn_bridge(connector); > > > + struct edid *edid = pdata->edid; > > > + int num, ret; > > > + > > > + if (!edid) { > > > + pm_runtime_get_sync(pdata->dev); > > > + edid = pdata->edid = drm_get_edid(connector, &pdata->aux.ddc); > > > + pm_runtime_put(pdata->dev); > > > > Is there any specific reason to use the indirect access method, compared > > to the direct method that translates access to an I2C ancillary address > > to an I2C-over-AUX transaction (see page 20 of SLLSEH2B) ? The direct > > method seems it would be more efficient. > > > > No I don't think it matters. I was just using the existing support code > that Sean wrote instead of digging into the details. Maybe Sean ran into > something earlier and abandoned that approach? >From reading the docs, it sounds as if there _could_ be a reason to use the indirect method. Specifically if the i2c host that the bridge is on doesn't support clock stretching then the direct method wouldn't work according to the docs. Is that something that we'd have to reasonably worry about? -Doug