linux-kernel - [PATCH v4 0/5] Pinephone video out fixes (flipping between two frames)

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Date: Sun, 10 Mar 2024 14:21:10 +0100
From: Frank Oltmanns <frank@...manns.dev>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
 Jernej Skrabec <jernej.skrabec@...il.com>, 
 Samuel Holland <samuel@...lland.org>, 
 Guido Günther <agx@...xcpu.org>, 
 Purism Kernel Team <kernel@...i.sm>, Ondrej Jirman <megi@....cz>, 
 Neil Armstrong <neil.armstrong@...aro.org>, 
 Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
 Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
 Frank Oltmanns <frank@...manns.dev>, stable@...r.kernel.org, 
 Diego Roversi <diegor@...cali.it>, Erico Nunes <nunes.erico@...il.com>
Subject: [PATCH v4 0/5] Pinephone video out fixes (flipping between two
 frames)

On some pinephones the video output sometimes freezes (flips between two
frames) [1]. It seems to be that the reason for this behaviour is that
PLL-MIPI is outside its limits, and the GPU is not running at a fixed
rate.

In this patch series I propose the following changes:
  1. sunxi-ng: Adhere to the following constraints given in the
     Allwinner A64 Manual regarding PLL-MIPI:
      * M/N <= 3
      * (PLL_VIDEO0)/M >= 24MHz
      * 500MHz <= clockrate <= 1400MHz

  2. Remove two operating points from the A64 DTS OPPs, so that the GPU
     runs at a fixed rate of 432 MHz.

Note, that when pinning the GPU to 432 MHz the issue [1] completely
disappears for me. I've searched the BSP and could not find any
indication that supports the idea of having the three OPPs. The only
frequency I found in the BPSs for A64 is 432 MHz, which has also proven
stable for me.

I very much appreciate your feedback!

[1] https://gitlab.com/postmarketOS/pmaports/-/issues/805

Signed-off-by: Frank Oltmanns <frank@...manns.dev>
---
Changes in v4:
- sunxi-ng: common: Address review comments.
- Link to v3: https://lore.kernel.org/r/20240304-pinephone-pll-fixes-v3-0-94ab828f269a@oltmanns.dev

Changes in v3:
- dts: Pin GPU to 432 MHz.
- nkm and a64: Move minimum and maximum rate handling to the common part
  of the sunxi-ng driver.
- Removed st7703 patch from series.
- Link to v2: https://lore.kernel.org/r/20240205-pinephone-pll-fixes-v2-0-96a46a2d8c9b@oltmanns.dev

Changes in v2:
- dts: Increase minimum GPU frequency to 192 MHz.
- nkm and a64: Add minimum and maximum rate for PLL-MIPI.
- nkm: Use the same approach for skipping invalid rates in
  ccu_nkm_find_best() as in ccu_nkm_find_best_with_parent_adj().
- nkm: Improve names for ratio struct members and hence get rid of
  describing comments.
- nkm and a64: Correct description in the commit messages: M/N <= 3
- Remove patches for nm as they were not needed.
- st7703: Rework the commit message to cover more background for the
  change.
- Link to v1: https://lore.kernel.org/r/20231218-pinephone-pll-fixes-v1-0-e238b6ed6dc1@oltmanns.dev

---
Frank Oltmanns (5):
      clk: sunxi-ng: common: Support minimum and maximum rate
      clk: sunxi-ng: a64: Set minimum and maximum rate for PLL-MIPI
      clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate
      clk: sunxi-ng: a64: Add constraints on PLL-MIPI's n/m ratio and parent rate
      arm64: dts: allwinner: a64: Run GPU at 432 MHz

 arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi |  8 --------
 drivers/clk/sunxi-ng/ccu-sun50i-a64.c         | 14 +++++++++-----
 drivers/clk/sunxi-ng/ccu_common.c             | 19 +++++++++++++++++++
 drivers/clk/sunxi-ng/ccu_common.h             |  3 +++
 drivers/clk/sunxi-ng/ccu_nkm.c                | 21 +++++++++++++++++++++
 drivers/clk/sunxi-ng/ccu_nkm.h                |  2 ++
 6 files changed, 54 insertions(+), 13 deletions(-)
---
base-commit: dcb6c8ee6acc6c347caec1e73fb900c0f4ff9806
change-id: 20231218-pinephone-pll-fixes-0ccdfde273e4

Best regards,
-- 
Frank Oltmanns <frank@...manns.dev>