From: Doug Anderson <dianders@chromium.org>
To: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: "open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
alsa-devel@alsa-project.org,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
Andy Yan <andy.yan@rock-chips.com>,
Yakir Yang <ykk@rock-chips.com>,
Fabio Estevam <fabio.estevam@freescale.com>,
Mark Brown <broonie@kernel.org>, Takashi Iwai <tiwai@suse.de>,
Jaroslav Kysela <perex@perex.cz>,
Sascha Hauer <s.hauer@pengutronix.de>,
Jon Nettleton <jon.nettleton@gmail.com>,
David Airlie <airlied@linux.ie>
Subject: Re: [PATCH 8/9] drm: bridge/dw_hdmi: replace CTS calculation for the ACR
Date: Fri, 4 Sep 2015 13:00:11 -0700 [thread overview]
Message-ID: <CAD=FV=X6Qhuw6DF7HFqQ-uMMC1TRRNYoPZs=aUhqs9q--gEO3w@mail.gmail.com> (raw)
In-Reply-To: <E1ZO6hm-0003Ni-E0@rmk-PC.arm.linux.org.uk>
Russell,
On Sat, Aug 8, 2015 at 9:10 AM, Russell King
<rmk+kernel@arm.linux.org.uk> wrote:
> Given the TDMS clock, audio sample rate, and the N parameter, we can
> calculate the CTS value for the audio clock regenerator (ACR) using the
> following calculation given in the HDMI specification:
>
> CTS = ftdms * N / (128 * fs)
>
> The specification says that the CTS value is an average value, which is
> true if the source hardware measures it. Where source hardware needs it
> to be programmed, it is particularly difficult to alternate it between
> two values correctly to ensure that we achieve a correct "average"
> fractional value at the sink.
>
> Also, there's the problem that our "ftdms" is not a fully accurate
> value; it is rounded to a kHz value. This introduces an unnecessary
> (and harmless) fractional value into the above equation for combinations
> like 148.5MHz/1.001 for 44100Hz - we still calculate the correct CTS
> value.
>
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
> drivers/gpu/drm/bridge/dw_hdmi.c | 92 +++++++---------------------------------
> 1 file changed, 16 insertions(+), 76 deletions(-)
If you take my feedback about your "drm: bridge/dw_hdmi: adjust pixel
clock values in N calculation" patch [1], all this math just works out
to "cts = pixel_clk / 1000". ...but doing the math does future proof
us a bit, so it seems like a good idea.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
[1] https://patchwork.kernel.org/patch/6975221/
next prev parent reply other threads:[~2015-09-04 20:00 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-08 16:02 [PATCH 00/12] dw-hdmi development Russell King - ARM Linux
2015-08-08 16:03 ` [PATCH 01/12] drm: bridge/dw_hdmi: remove pixel repetition setting for all VICs Russell King
2015-08-08 16:03 ` [PATCH 02/12] drm: bridge/dw_hdmi: don't support any pixel doubled modes Russell King
2015-08-08 16:03 ` [PATCH 03/12] gpu: imx: simplify sync polarity setting Russell King
2015-10-06 17:57 ` Fabio Estevam
2015-08-08 16:03 ` [PATCH 04/12] gpu: imx: fix support for interlaced modes Russell King
2015-08-27 8:39 ` Philipp Zabel
2015-08-27 8:54 ` Russell King - ARM Linux
2015-08-27 9:40 ` Philipp Zabel
2015-10-06 17:59 ` Fabio Estevam
2015-08-08 16:03 ` [PATCH 05/12] drm: bridge/dw_hdmi: add support for interlaced video modes Russell King
2015-10-06 18:00 ` Fabio Estevam
2015-08-08 16:03 ` [PATCH 06/12] drm: bridge/dw_hdmi: clean up HDMI vs DVI mode handling Russell King
2015-10-07 3:40 ` Yakir Yang
2015-08-08 16:03 ` [PATCH 07/12] drm: bridge/dw_hdmi: enable audio only if sink supports audio Russell King
2015-10-07 3:42 ` Yakir Yang
2015-08-08 16:04 ` [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in mode_set Russell King
2015-10-07 3:50 ` Yakir Yang
2015-10-07 9:18 ` Russell King - ARM Linux
2015-10-07 9:35 ` Yakir Yang
2015-08-08 16:04 ` [PATCH 09/12] drm: bridge/dw_hdmi: rename dw_hdmi_phy_enable_power() Russell King
2015-08-08 16:04 ` [PATCH 10/12] drm: bridge/dw_hdmi: fix phy enable/disable handling Russell King
[not found] ` <56149A11.4070102@rock-chips.com>
2015-10-07 9:48 ` Russell King - ARM Linux
[not found] ` <5614F68B.6050808@rock-chips.com>
2015-10-07 19:17 ` Russell King - ARM Linux
2015-10-08 8:35 ` Yakir Yang
2015-08-08 16:04 ` [PATCH 11/12] drm: bridge/dw_hdmi: add connector mode forcing Russell King
2015-10-06 18:01 ` Fabio Estevam
2015-08-08 16:04 ` [PATCH 12/12] drm: bridge/dw_hdmi: improve HDMI enable/disable handling Russell King
2015-10-06 18:03 ` Fabio Estevam
2015-08-08 16:09 ` [PATCH 0/9] dw-hdmi audio support Russell King - ARM Linux
2015-08-08 16:10 ` [PATCH 1/9] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-08-10 10:05 ` Takashi Iwai
2015-08-10 10:39 ` Russell King - ARM Linux
2015-08-10 12:23 ` Takashi Iwai
2015-08-10 16:49 ` Russell King - ARM Linux
2015-08-10 18:16 ` Mark Brown
2015-08-14 13:54 ` [PATCH v2 1/9] drm: bridge/dw_hdmi-ahb-audio: add audio driver David Airlie <airlied@linux.ie>, Sascha Hauer <s.hauer@pengutronix.de>, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Jaroslav Kysela <perex@perex.cz>, linux-rockchip@lists.infradead.org, Mark Brown <broonie@kernel.org>, Philipp Zabel <p.zabel@pengutronix.de>, Yakir Yang <ykk@rock-chips.com>, Andy Yan <andy.yan@rock-chips.com>, Jon Nettleton <jon.nettleton@gmail.com>, linux-arm-kernel@lists.infradead.org Russell King
2015-08-14 14:04 ` [PATCH v2 1/9] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-08-14 14:34 ` [alsa-devel] " Takashi Iwai
2015-10-06 18:07 ` [PATCH " Fabio Estevam
2015-10-06 18:18 ` Russell King - ARM Linux
2015-10-06 18:45 ` Fabio Estevam
2015-10-06 18:54 ` Russell King - ARM Linux
2015-10-06 20:25 ` Fabio Estevam
2015-10-09 16:00 ` Russell King - ARM Linux
2015-10-09 16:02 ` Fabio Estevam
2015-10-09 16:11 ` Russell King - ARM Linux
2015-08-08 16:10 ` [PATCH 2/9] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-08-08 16:10 ` [PATCH 3/9] drm: bridge/dw_hdmi-ahb-audio: basic support for multi-channel PCM audio Russell King
2015-08-08 16:10 ` [PATCH 4/9] drm: bridge/dw_hdmi-ahb-audio: allow larger buffer sizes Russell King
2015-08-08 16:10 ` [PATCH 5/9] drm: bridge/dw_hdmi: avoid being recursive in N calculation Russell King
2015-09-04 17:50 ` Doug Anderson
2015-08-08 16:10 ` [PATCH 6/9] drm: bridge/dw_hdmi: adjust pixel clock values " Russell King
2015-09-04 18:21 ` Doug Anderson
2015-09-04 19:48 ` Doug Anderson
2015-09-04 21:24 ` Russell King - ARM Linux
2015-09-04 23:50 ` Doug Anderson
2015-09-05 0:27 ` Russell King - ARM Linux
2015-09-05 2:03 ` Doug Anderson
2015-09-05 8:31 ` Russell King - ARM Linux
2015-09-05 13:46 ` Doug Anderson
2015-09-05 14:01 ` Russell King - ARM Linux
2015-09-05 19:44 ` Doug Anderson
2015-09-05 8:34 ` Russell King - ARM Linux
2015-09-05 13:50 ` Doug Anderson
2015-08-08 16:10 ` [PATCH 7/9] drm: bridge/dw_hdmi: remove ratio support from ACR code Russell King
2015-09-04 18:24 ` Doug Anderson
2015-08-08 16:10 ` [PATCH 8/9] drm: bridge/dw_hdmi: replace CTS calculation for the ACR Russell King
2015-09-04 20:00 ` Doug Anderson [this message]
2015-08-08 16:10 ` [PATCH 9/9] drm: bridge/dw_hdmi-i2s-audio: add audio driver Russell King
2015-08-10 15:48 ` Russell King - ARM Linux
2015-08-10 16:26 ` Yakir Yang
2015-08-27 8:42 ` [PATCH 0/9] dw-hdmi audio support Philipp Zabel
2016-01-05 15:40 ` [alsa-devel] " Jean-Michel Hautbois
2016-01-05 15:54 ` Fabio Estevam
2016-01-05 16:04 ` Russell King - ARM Linux
2016-01-07 8:21 ` Jean-Michel Hautbois
2015-08-10 12:21 ` [PATCH 00/12] dw-hdmi development Thierry Reding
2015-08-18 10:37 ` Russell King - ARM Linux
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