linux-kernel - [PATCH RFC v2 0/2] drm/meson: vclk: revert and re-fix vclk calculations

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Message-ID: <20250421201300.778955-1-martin.blumenstingl@googlemail.com>
Date: Mon, 21 Apr 2025 22:12:58 +0200
From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To: dri-devel@...ts.freedesktop.org,
	linux-amlogic@...ts.infradead.org
Cc: neil.armstrong@...aro.org,
	christianshewitt@...il.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH RFC v2 0/2] drm/meson: vclk: revert and re-fix vclk calculations

This is a successor of a previous patchset by Christian [0]

Patch 1 reverts a previous fix for loss of HDMI sync when playing YUV420
@ 59.94 media. The patch does resolve a calculation issue. It also makes
all fractional rates invalid which is a bigger problem.

Patch 2 changes the whole drm/meson driver to use Hz as unit for clocks/
frequencies. And importantly it uses the relevant 64-bit maths helpers so
the code can still be compiled using for 32-bit ARM.
Maxime previously suggested using drm_hdmi_compute_mode_clock(). That's
still something to implement with future patches.

Neil, I'd like to hear your feedback on this approach.

[0] https://lore.kernel.org/linux-amlogic/20250110074458.3624094-1-christianshewitt@gmail.com/

Christian Hewitt (1):
  Revert "drm/meson: vclk: fix calculation of 59.94 fractional rates"

Martin Blumenstingl (1):
  drm/meson: use unsigned long long / Hz for frequency types

 drivers/gpu/drm/meson/meson_drv.c          |   2 +-
 drivers/gpu/drm/meson/meson_drv.h          |   2 +-
 drivers/gpu/drm/meson/meson_encoder_hdmi.c |  29 +--
 drivers/gpu/drm/meson/meson_vclk.c         | 195 +++++++++++----------
 drivers/gpu/drm/meson/meson_vclk.h         |  13 +-
 5 files changed, 126 insertions(+), 115 deletions(-)

-- 
2.49.0