linux-kernel - Re: [PATCH 0/5] Set max rate for video PLLs

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Date:   Mon, 20 Aug 2018 15:36:47 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     wens@...e.org, mturquette@...libre.com, sboyd@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH 0/5] Set max rate for video PLLs

On Thu, Aug 09, 2018 at 06:52:12PM +0200, Jernej Skrabec wrote:
> This patch series implement maximum rate constraint for video PLLs,
> because it is possible to set higher PLL rate that is actually
> supported in HW.
> 
> Issue became apparent when user reported non-working monitor connected
> to board with H5 SoC. Native monitor resolution in this case was
> 2560x1080, with 185580 kHz pixel clock. Clock subsystem found out that
> best matching pixel clock can be generated if video PLL is set to 2040
> MHz, which is way out of specs for PLL. With this patch series applied,
> everything worked just fine, with slightly higher rate error, but within
> working limits for PLL and HDMI.
> 
> I'm not sure if "Fixes" tag should be added. It solves real world
> problem, but there was nothing wrongly implemented, just upper limit
> is missing.
> 
> While user reported that these patches solve the issue on H5, I added
> similar fixes for other SoCs too. Since I don't have such monitor,
> I only tested if board boots up and if HDMI works (H3, R40 and A83T).

Queued for 4.20, thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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