linux-kernel - [PATCH v3 0/2] phy: Add support for the HDMI TX PHY on Meson8/8b/8m2

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Date:   Wed, 20 Oct 2021 21:51:05 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-phy@...ts.infradead.org, vkoul@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        robh+dt@...nel.org, kishon@...com,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH v3 0/2] phy: Add support for the HDMI TX PHY on Meson8/8b/8m2

Amlogic Meson8/8b/8m2 SoCs embed a HDMI TX PHY. Unfortunately there is
no (public) documentation for this hardware. The best thing we have is
the 3.10 vendor kernel, which unfortunately doesn't document most
register bits (only a few are named there, the rest is all magic
numbers).
It is possible that this is a TranSwitch HDMI TX PHY based core, but
this is pure speculation.

Adding a driver for the HDMI TX PHY gets us one step closer to video
output on these older SoCs.


Changes since v2 at [1]:
- Use "amlogic,meson8-hdmi-tx-phy" as fallback compatible string for
  Meson8b and Meson8m2. This affects both patches in this series and
  it's the reason why I dropped Rob's Reviewed-by.
- Add a comment to the driver explaining that there no detailed
  register documentation (naming) is available and that's why we also
  use some magic values in the driver as suggested by Vinod.
- Hardcode the HHI_HDMI_PHY_CNTL* register offsets (from the HHI area)
  directly in the driver instead of using some incomplete "reg" property
  parsing code. This also makes it easier to compare the register values
  with the vendor kernel sources and datasheets as the offset doesn't
  have to be added/subtracted when comparing the values.


Changes since v1 at [0]:
- add a reg property to the dt-bindings
- parse the reg property (register offset) in the driver
- update copyright year to 2021 (spotted by Vinod, thanks!)
- drop "default ARCH_MESON" from the Kconfig entry


[0] https://patchwork.kernel.org/project/linux-amlogic/cover/20210604190338.2248295-1-martin.blumenstingl@googlemail.com/
[1] https://patchwork.kernel.org/project/linux-amlogic/cover/20210629182047.893415-1-martin.blumenstingl@googlemail.com/


Martin Blumenstingl (2):
  dt-bindings: phy: Add the Amlogic Meson8 HDMI TX PHY bindings
  phy: amlogic: Add a new driver for the HDMI TX PHY on Meson8/8b/8m2

 .../phy/amlogic,meson8-hdmi-tx-phy.yaml       |  65 +++++++
 drivers/phy/amlogic/Kconfig                   |  10 ++
 drivers/phy/amlogic/Makefile                  |   1 +
 drivers/phy/amlogic/phy-meson8-hdmi-tx.c      | 160 ++++++++++++++++++
 4 files changed, 236 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/phy/amlogic,meson8-hdmi-tx-phy.yaml
 create mode 100644 drivers/phy/amlogic/phy-meson8-hdmi-tx.c

-- 
2.33.1