Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935823AbdCJKWO (ORCPT ); Fri, 10 Mar 2017 05:22:14 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:38414 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933496AbdCJKWH (ORCPT ); Fri, 10 Mar 2017 05:22:07 -0500 Subject: Re: [PATCH] drm: dw_hdmi: Gate audio sampler clock from the enablement functions To: Russell King - ARM Linux References: <20170310093509.19044-1-romain.perier@collabora.com> <20170310094613.GQ21222@n2100.armlinux.org.uk> Cc: Archit Taneja , David Airlie , Heiko Stuebner , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org From: Romain Perier Message-ID: <7888eb1f-2781-d4ed-6f26-cb76e1ead4d2@collabora.com> Date: Fri, 10 Mar 2017 11:21:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170310094613.GQ21222@n2100.armlinux.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1404 Lines: 28 Hello, Le 10/03/2017 ? 10:46, Russell King - ARM Linux a ?crit : > On Fri, Mar 10, 2017 at 10:35:09AM +0100, Romain Perier wrote: >> Currently, the audio sampler clock is enabled from dw_hdmi_setup() at >> step E. and is kept enabled for later use. This clock should be enabled >> and disabled along with the actual audio stream and not always on (that >> is bad for PM). Futhermore, this might cause sound glitches with some >> HDMI devices, as the CTS+N is forced to zero when the stream is disabled >> while the audio clock is still running. >> >> This commit adds a parameter to hdmi_audio_enable_clk() that controls >> when the audio sample clock must be enabled or disabled. Then, it moves >> the call to this function into dw_hdmi_audio_enable() and >> dw_hdmi_audio_disable(). > How does this interact with the workaround given in my commit introducing > these functions? (Commit b90120a96608). > > Setting N=0 is a work-around for iMX6, and we need the audio FIFO to be > loaded with data prior to setting N non-zero. If disabling the audio > clock prevents the audio FIFO being loaded, your patch will break iMX6. > Mhhh, the fact is I have no IMX6 devices here (only Rockchip). So I only tested on Rockchip devices. An approach might be to introduce an option for handling this errata, because that's platform specific and other platforms (like Rockchip) are in conflict with this. Romain