[PATCH 0/3] phy: rockchip: emmc: Enable internal strobe pull-down by default

[Folker Schwesinger via B4 Relay]

Various RK3399 boards, including the Rock Pi 4 series, the NanoPi 4
series and possibly others showed instabilities with some eMMC modules
when operating in HS400 mode [1]. Later, a missing pull-down resistor on
the eMMC strobe line was identified as the root cause of these
instabilities [2].

This series changes the Rockchip eMMC PHY driver to enable the
internal pull-down for the strobe line by default, effectively
restoring the behavior of the vendor kernel [3].
Addressing the problem in the driver avoids fix-ups in individual
board DTs.

As this change makes the optional DT property enable-strobe-pulldown
obsolete, it is replaced by a new property disable-strobe-pulldown,
that, when used, allows to disable the internal pull-down.

While at it, the enable-strobe-pulldown property was removed from the
NanoPi4 series DTS (which was the only user of the property in the kernel).

[1]: https://lore.kernel.org/all/20230705144255.115299-1-chris.obbard@xxxxxxxxxxxxx/
[2]: https://lore.kernel.org/all/20220822074139.3810-1-jensenhuang@xxxxxxxxxxxxxxx/
[3]: https://github.com/rockchip-linux/kernel/blob/develop-4.4/drivers/phy/rockchip/phy-rockchip-emmc.c#L310

Signed-off-by: Folker Schwesinger <dev@xxxxxxxxxxxxxxxxxxxxx>
---
Folker Schwesinger (3):
      phy: rockchip: emmc: Enable pulldown for strobe line
      devicetree: phy: rockchip-emmc: Document changed strobe-pulldown property
      arm64: dts: rockchip: Remove enable-strobe-pulldown for NanoPi4 boards

 Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt | 4 ++--
 arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi            | 1 -
 drivers/phy/rockchip/phy-rockchip-emmc.c                    | 6 +++---
 3 files changed, 5 insertions(+), 6 deletions(-)
---
base-commit: 4cece764965020c22cff7665b18a012006359095
change-id: 20240326-rk-default-enable-strobe-pulldown-3356c8cf1b4f

Best regards,
-- 
Folker Schwesinger <dev@xxxxxxxxxxxxxxxxxxxxx>