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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1ghfxS-0002UJ-5L; Thu, 10 Jan 2019 19:25:38 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1ghfxN-0002TM-9o for linux-arm-kernel@lists.infradead.org; Thu, 10 Jan 2019 19:25:36 +0000 Received: from bbrezillon (91-160-177-164.subs.proxad.net [91.160.177.164]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8B8C220651; Thu, 10 Jan 2019 19:25:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547148331; bh=/vR7LskhHHSTMwzevIJBqkXpkfEf+ABm3ogsIzBsb7A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fIJpWIzwCdjQEVAZMDq4Sh4f4Spa7TVjYDR++txQnfi9dt8G1NrWTnSCC1pXE1Wz6 kCe+BtkENC9yf+/aKLqxIFroKdM6mQkex7hzm3e0NGbrPp1sFTNuX1cpuQgZqf74Zd ZQFaqlTSB/hfEdogklntQVSZCa3sSBn2T1IPHfBc= Date: Thu, 10 Jan 2019 20:25:22 +0100 From: Boris Brezillon To: Peter Rosin Subject: Re: [PATCH 4/4] drm/atmel-hlcdc: do not immediately disable planes, wait for next frame Message-ID: <20190110202522.10206f2d@bbrezillon> In-Reply-To: References: <20190110151020.30468-1-peda@axentia.se> <20190110151020.30468-5-peda@axentia.se> <20190110182904.5efd08f2@bbrezillon> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190110_112534_319680_5DDB93C7 X-CRM114-Status: GOOD ( 19.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexandre Belloni , David Airlie , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Boris Brezillon , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 10 Jan 2019 18:51:21 +0000 Peter Rosin wrote: > On 2019-01-10 18:29, Boris Brezillon wrote: > > On Thu, 10 Jan 2019 15:10:48 +0000 > > Peter Rosin wrote: > > > >> The A2Q and UPDATE bits have no effect in the channel disable registers. > >> However, since they are present, assume that the intention is to disable > >> planes, not immediately as indicated by the RST bit, but on the next > >> frame shift since that is what A2Q and UPDATE means in the channel enable > >> registers. > >> > >> Disabling the plane on the next frame shift is done with the EN bit, > >> so use that. > > > > It's been a long time, but I think I had a good reason for forcing a > > reset. IIRC, when you don't do that and the CRTC is disabled before the > > plane, the EN bit stays around, and next time you queue a plane update, > > you'll start with an invalid buf pointer. > > It might be possible to clear the EN bit in ...CHDR before enabling the > plane in ...CHER. Or is that too late? I think I tried that, but I'm not sure (BTW, this change was done in bd4248bb5e8b ("drm: atmel-hlcdc: reset layer A2Q and UPDATE bits when disabling it")). Anyway, I'm not even sure this is still needed now that atomic updates have a wait_for_flip_done/vblank() in the commit path. > But this patch is not overly > important, I just wanted to avoid the resulting "black hole" when the > plane DMA is disabled mid-frame. But disabling planes is probably not > something that happens frequently and will perhaps not be noticed at > all... Okay. Other patches look good to me, I'm just waiting for Nicolas feedback before applying them. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel