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 C29FBCD37B0 for ; Mon, 18 Sep 2023 21:01:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230070AbjIRVB0 (ORCPT ); Mon, 18 Sep 2023 17:01:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229680AbjIRVBZ (ORCPT ); Mon, 18 Sep 2023 17:01:25 -0400 Received: from aposti.net (aposti.net [89.234.176.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AAF1B90; Mon, 18 Sep 2023 14:01:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=crapouillou.net; s=mail; t=1695070877; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PGvKmZ4gaTSql+5Gg/EmBcBsE1/45EteF32nr/hxcZo=; b=ijlY7zatBWXUmIxq4VkOLaBZC2y/y4fDubHLt9REXR9DJhzjsscveIfKT8vlGE8SvHjBhp iMRuIIreS9ezl3Xt6wHwmc+6ryYcL/rw+KMW6mrpRkDtAZJc3tB6zmqros4UFA7XpU1XSE FQqp4lIKDXcTMUEZGMhTp/Ml8h3Sm7E= Message-ID: <4d2079d66249a7052acded0abf30169a4e95d151.camel@crapouillou.net> Subject: Re: [RFC PATCH v2 3/9] drm/panel: nv3052c: Sleep for 150ms after reset From: Paul Cercueil To: John Watts , Jessica Zhang Cc: dri-devel@lists.freedesktop.org, Neil Armstrong , Sam Ravnborg , David Airlie , Daniel Vetter , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Shawn Guo , Heiko Stuebner , Chris Morgan , Jagan Teki , Christophe Branchereau , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 18 Sep 2023 23:01:15 +0200 In-Reply-To: References: <20230918125853.2249187-1-contact@jookia.org> <20230918125853.2249187-4-contact@jookia.org> <7fc1ca68-ca7c-59b2-0b70-27bc34d83cee@quicinc.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi John, Le mardi 19 septembre 2023 =C3=A0 06:52 +1000, John Watts a =C3=A9crit=C2= =A0: > On Mon, Sep 18, 2023 at 01:19:03PM -0700, Jessica Zhang wrote: > > Hi John, > >=20 > > Just wondering, is there some context to this change? I.e., was > > this made to > > fix a specific issue? > >=20 > > This seems like a pretty significant increase in wait time so, if > > it's not a > > fix, I'm not sure if this would be an improvement on the current > > behavior. > >=20 > > Thanks, > >=20 > > Jessica Zhang >=20 > Hi Jessica, >=20 > Thank you for the feedback. >=20 > This patch here is required by the data sheet if the screen was > already running > and was reset. This is necessary if for example the bootloader set up > and had > the screen running. However I have not tested this, it's possible the > specific > panels have shorter tolerances for resets. This is purely > precautionary at > this stage based on what the data sheet says. >=20 > That said I will be investigating this specific use case with this > panel over > the next few months. I am okay separating out this patch until I have > proof it's > needed for my particular display. I don't know anything about the ltk > display. >=20 > The second sleep patch can probably be omitted as I don't think the > panel being > prepared then unprepared in rapid succession is a realistic > situation, but I=20 > figured I might as well propose it to see if it's the right thing to > do. >=20 > Thanks for your time and review, > John. The datasheet does say a 5ms sleep time is necesary after a reset. I assume the 120ms delay you quote is when a *software* reset is performed in Sleep-out mode. The code here does a hard-reset. Cheers, -Paul