From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752554AbdCMJhB (ORCPT ); Mon, 13 Mar 2017 05:37:01 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:55786 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752023AbdCMJgq (ORCPT ); Mon, 13 Mar 2017 05:36:46 -0400 Date: Mon, 13 Mar 2017 09:36:30 +0000 From: Russell King - ARM Linux To: Neil Armstrong Cc: Romain Perier , Jose Abreu , 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 Subject: Re: [PATCH] drm: dw_hdmi: Gate audio sampler clock from the enablement functions Message-ID: <20170313093630.GE21222@n2100.armlinux.org.uk> References: <20170310093509.19044-1-romain.perier@collabora.com> <25ad96a7-d907-2bcb-3a96-15a2956e7652@baylibre.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <25ad96a7-d907-2bcb-3a96-15a2956e7652@baylibre.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 13, 2017 at 10:27:08AM +0100, Neil Armstrong wrote: > On 03/10/2017 10:35 AM, 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(). > > > > Signed-off-by: Romain Perier > > --- > > drivers/gpu/drm/bridge/dw-hdmi.c | 15 +++++++++------ > > 1 file changed, 9 insertions(+), 6 deletions(-) > > > > Hi Romain, Russell, Jose, > > This is a little out of scope, but I was wondering why the CTS calculation > was not left in AUTO mode in the dw-hdmi driver ? There is no indication in the iMX6 manuals that the iMX6 supports automatic CTS calculation. Bits 7:4 of the AUD_CTS3 register are marked as "reserved". We're reliant on the information in the iMX6 manuals as we don't have access to Synopsis' databooks for these parts (I understand you have to be a customer to have access to that.) -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@armlinux.org.uk (Russell King - ARM Linux) Date: Mon, 13 Mar 2017 09:36:30 +0000 Subject: [PATCH] drm: dw_hdmi: Gate audio sampler clock from the enablement functions In-Reply-To: <25ad96a7-d907-2bcb-3a96-15a2956e7652@baylibre.com> References: <20170310093509.19044-1-romain.perier@collabora.com> <25ad96a7-d907-2bcb-3a96-15a2956e7652@baylibre.com> Message-ID: <20170313093630.GE21222@n2100.armlinux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Mar 13, 2017 at 10:27:08AM +0100, Neil Armstrong wrote: > On 03/10/2017 10:35 AM, 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(). > > > > Signed-off-by: Romain Perier > > --- > > drivers/gpu/drm/bridge/dw-hdmi.c | 15 +++++++++------ > > 1 file changed, 9 insertions(+), 6 deletions(-) > > > > Hi Romain, Russell, Jose, > > This is a little out of scope, but I was wondering why the CTS calculation > was not left in AUTO mode in the dw-hdmi driver ? There is no indication in the iMX6 manuals that the iMX6 supports automatic CTS calculation. Bits 7:4 of the AUD_CTS3 register are marked as "reserved". We're reliant on the information in the iMX6 manuals as we don't have access to Synopsis' databooks for these parts (I understand you have to be a customer to have access to that.) -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.