Re: [PATCH v1] drm/meson: fix more rounding issues with 59.94Hz modes

From: Neil Armstrong <neil.armstrong@linaro.org>
To: linux-amlogic@lists.infradead.org,
	dri-devel@lists.freedesktop.org,
	 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v1] drm/meson: fix more rounding issues with 59.94Hz modes
Date: Tue, 10 Jun 2025 14:17:13 +0200	[thread overview]
Message-ID: <174955783398.1721274.13530320235871545331.b4-ty@linaro.org> (raw)
In-Reply-To: <20250609202751.962208-1-martin.blumenstingl@googlemail.com>

Hi,

On Mon, 09 Jun 2025 22:27:51 +0200, Martin Blumenstingl wrote:
> Commit 1017560164b6 ("drm/meson: use unsigned long long / Hz for
> frequency types") attempts to resolve video playback using 59.94Hz.
>  using YUV420 by changing the clock calculation to use
> Hz instead of kHz (thus yielding more precision).
> 
> The basic calculation itself is correct, however the comparisions in
> meson_vclk_vic_supported_freq() and meson_vclk_setup() don't work
> anymore for 59.94Hz modes (using the freq * 1000 / 1001 logic). For
> example, drm/edid specifies a 593407kHz clock for 3840x2160@59.94Hz.
> With the mentioend commit we convert this to Hz. Then meson_vclk
> tries to find a matchig "params" entry (as the clock setup code
> currently only supports specific frequencies) by taking the venc_freq
> from the params and calculating the "alt frequency" (used for the
> 59.94Hz modes) from it, which is:
>   (594000000Hz * 1000) / 1001 = 593406593Hz
> 
> [...]

Thanks, Applied to https://gitlab.freedesktop.org/drm/misc/kernel.git (drm-misc-fixes)

[1/1] drm/meson: fix more rounding issues with 59.94Hz modes
      https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/0cee6c4d3518b2e757aedae78771f17149f57653

-- 
Neil


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