On Amlogic chipsets, the bias set through pinconf applies to the pad itself, not only the GPIO function. This means that even when we change the function of the pad from GPIO to anything else, the bias previously set still applies.
While trying to boot from SPI, I noticed the eMMC was not working anymore. Even if the related eMMC pad are not used by the SPI, the ROM code sets a pull-down on the eMMC pad and leaves it that way. This breaks the eMMC later on, in both u-boot and Linux. The underlying issue is that we inherit whatever was left by previous user of the pad (pinconf, u-boot or the ROM code). As a consequence, the actual setup we get is undefined. There is nothing mentioned in the documentation about pad bias and pinmux function, however leaving it undefined is not an option. This patchset consistently disable the pad bias for every pinmux functions. It seems to work well, we can only assume that the necessary bias (if any) is already provided by the pin function itself. I can't really test every pinmux configuration and it is fairly possible I missed something so it would be nice if more people could confirm if nothing (new) is broken after applying this series. One things could be the i2c. Usually the i2c pull-ups are physically present on the board but, if they are missing on platform, we may define a special pinmux setting with pull-up enabled. One last gotcha, I recently posted fixups around bias setting to pinctrl which have been merged: [0] [1]. These must be applied before applying this series, otherwise when requesting 'bias-disable' you'll probably get a pull-down instead. Changes since v1 [2]: * Fix wrongly placed bias-disable on meson8 [0]: https://lkml.kernel.org/r/20181023160319.27003-1-jbru...@baylibre.com [1]: https://lkml.kernel.org/r/20181029151340.9087-1-jbru...@baylibre.com [2]: https://lkml.kernel.org/r/20181108104426.1877-1-jbru...@baylibre.com Jerome Brunet (4): arm64: dts: meson: remove extra subnode in mmc clk_gate pinmux arm64: dts: meson: disable pad bias for mmc pinmuxes arm64: dts: meson: consistently disable pin bias ARM: dts: meson: consistently disable pin bias arch/arm/boot/dts/meson8.dtsi | 12 +++ arch/arm/boot/dts/meson8b.dtsi | 9 ++ arch/arm/boot/dts/meson8m2.dtsi | 1 + arch/arm64/boot/dts/amlogic/meson-axg.dtsi | 111 ++++++++++++++++++-- arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi | 60 +++++++++-- arch/arm64/boot/dts/amlogic/meson-gxl.dtsi | 62 +++++++++-- 6 files changed, 231 insertions(+), 24 deletions(-) -- 2.19.1
