Re: [PATCH 6/9] drm: bridge/dw_hdmi: adjust pixel clock values in N calculation - Russell King

From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Doug Anderson <dianders@chromium.org>
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	alsa-devel@alsa-project.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	Jaroslav Kysela <perex@perex.cz>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	Mark Brown <broonie@kernel.org>, Yakir Yang <ykk@rock-chips.com>,
	Andy Yan <andy.yan@rock-chips.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 6/9] drm: bridge/dw_hdmi: adjust pixel clock values in N calculation
Date: Sat, 5 Sep 2015 09:31:08 +0100	[thread overview]
Message-ID: <20150905083107.GK21084@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAD=FV=WR4iJ57FLh1d46-s9Gu-4wW6NdoROx-kNbbA0zFpUo0w@mail.gmail.com>

On Fri, Sep 04, 2015 at 07:03:11PM -0700, Doug Anderson wrote:
> AKA: just replace your entire "compute_n" function with:
> 
> return (128 * freq) / 1000;
> 
> ...and it's 100% simpler _and_ gets you a (marginally) better rate
> (assuming you really have 22.175000).  If it was just about a
> 32000.222 vs 32000 I'd not be saying anything right now.  It's about
> adding complexity.

No.  It doesn't work for all cases.  Do the calculations for every
sample rate in those tables in the HDMI spec, and you'll find out
why.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
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