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 B34DBCE7B1A for ; Thu, 28 Sep 2023 10:24:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231173AbjI1KYo (ORCPT ); Thu, 28 Sep 2023 06:24:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230239AbjI1KYl (ORCPT ); Thu, 28 Sep 2023 06:24:41 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E2DA126; Thu, 28 Sep 2023 03:24:40 -0700 (PDT) Received: from [192.168.1.100] (2-237-20-237.ip236.fastwebnet.it [2.237.20.237]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: kholk11) by madras.collabora.co.uk (Postfix) with ESMTPSA id AA06A6607330; Thu, 28 Sep 2023 11:24:37 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1695896678; bh=5hCbgR+BACDhVeYZKUOi0bMLQ8NC+PJjXquJc5GRf98=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Ld5ACCr/B7/IiU8odH20F4Td3WX4xDZs0EwgfnDXiFT9fZtAblS9mr9bwIGislksT e/pXGo5ahcuj5++F+CthhX4Jp9TmVkdI4Yqe/E4OaM5glFtKRu1LQKCDzZFANDd5pH AMbx6tm2ahnklinuCOPjkmDP1FaKGHqHVvofvuV+aIIPICtu0EyqVQCxj4teY4Pthu kih+i8XE9Y/9Jx5IOP960coCEZ6prEr+F5aYrA0nzyhfavnebCPP8kevL+zjW3LBez 1xMAm+Y8KOl1zGDGORtl+YEnmm9Y3gJMUp9LAHExSkM2FkWwoUZFA+SGgk4yf4w3Gn tsa0zBvWZp2Rw== Message-ID: <5d1669c0-64c3-8a5d-6f4e-88f72d4b40b4@collabora.com> Date: Thu, 28 Sep 2023 12:24:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [RESEND PATCH v6 17/20] drm/mediatek: Support MT8188 Padding in display driver Content-Language: en-US To: =?UTF-8?B?U2hhd24gU3VuZyAo5a6L5a2d6KyZKQ==?= , =?UTF-8?B?Q0sgSHUgKOiDoeS/iuWFiSk=?= , "matthias.bgg@gmail.com" , "robh+dt@kernel.org" , "krzysztof.kozlowski+dt@linaro.org" Cc: "linux-kernel@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , =?UTF-8?B?U2luZ28gQ2hhbmcgKOW8teiIiOWciyk=?= , =?UTF-8?B?SmFzb24tSkggTGluICjmnpfnnb/npaUp?= , "devicetree@vger.kernel.org" , =?UTF-8?B?TmFuY3kgTGluICjmnpfmrKPonqIp?= , "daniel@ffwll.ch" , "p.zabel@pengutronix.de" , "conor+dt@kernel.org" , "dri-devel@lists.freedesktop.org" , Project_Global_Chrome_Upstream_Group , "airlied@gmail.com" , "linux-arm-kernel@lists.infradead.org" , "nfraprado@collabora.com" References: <20230911074233.31556-1-shawn.sung@mediatek.com> <20230911074233.31556-18-shawn.sung@mediatek.com> <9fc58793d90b7a984dc3d40ac44719e9869b1202.camel@mediatek.com> From: AngeloGioacchino Del Regno In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 28/09/23 05:39, Shawn Sung (宋孝謙) ha scritto: > Hi CK, > > On Thu, 2023-09-28 at 03:05 +0000, CK Hu (胡俊光) wrote: >> Hi, Hsiao-chien: >> >> On Mon, 2023-09-11 at 15:42 +0800, Hsiao Chien Sung wrote: >>> Padding is a new display module on MT8188, it provides ability >>> to add pixels to width and height of a layer with specified colors. >>> >>> Due to hardware design, Mixer in VDOSYS1 requires width of a layer >>> to be 2-pixel-align, or 4-pixel-align when ETHDR is enabled, >>> we need Padding to deal with odd width. >>> >>> Please notice that even if the Padding is in bypass mode, >>> settings in register must be cleared to 0, >>> or undefined behaviors could happen. >> >> You just set padding to bypass mode and not clear settings to 0. Any >> thing wrong? >> > > Since the deafult value of all the registers in Padding is zero, and > we are not using Padding currently, it's fine if we just set padding to > bypass mode witout clearing other registers. > > The comment is just a reminder in case we forget it in the future. Do *not* rely on default register values, because you don't know what booted Linux in the first place: you shall *not* expect a clean state and you shall *not* expect a clean boot. Besides, what I see is that you're setting GENMASK(1, 0) without explaining why in the code: you have to add at least the definitions for PADDING_EN and PADDING_BYPASS. I also don't see why you shouldn't add at least basic handling for this block, as it looks easy enough: after all, you anyway have to make sure that the registers are cleared - might as well just add a little more effort on top and actually set them to meaningful values? That's ultimately your choice, but I don't want to see any GENMASK(31,0) write even for register clearing. Please make this driver proper. Thanks, Angelo > > Regards, > Hsiao Chien Sung