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SubjectRe: [PATCH] phy: rockchip-dp: Avoid power leak by leaving the PHY power on
Elaine and Caesar,

On Tue, May 7, 2019 at 4:50 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> While testing a newer kernel on rk3288-based Chromebooks I found that
> the power draw in suspend was higher on newer kernels compared to the
> downstream Chrome OS 3.14 kernel. Specifically the power of an
> rk3288-veyron-jerry board that I tested (as measured by the smart
> battery) was ~16 mA on Chrome OS 3.14 and ~21 mA on a newer kernel.
>
> I tracked the regression down to the fact that the "DP PHY" driver
> didn't exist in our downstream 3.14. We relied on the eDP driver to
> turn on the clock and relied on the fact that the power for the PHY
> was default turned on.
>
> Specifically the thing that caused the power regression was turning
> the eDP PHY _off_. Presumably there is some sort of power leak in the
> system and when we turn the PHY off something is leaching power from
> something else and causing excessive power draw.
>
> Doing a search through device trees shows that this PHY is only ever
> used on rk3288. Presumably this power leak is present on all
> rk3288-SoCs running upstream Linux so let's just whack the driver to
> make sure we never turn off power. We'll still leave the parts that
> turn _on_ the power and grab the clock, though.
>
> NOTES:
> A) If someone can identify what this power leak is and fix it in some
> other way we can revert this patch.
> B) If someone can show that their particular board doesn't have this
> power leak (maybe they have rails hooked up differently?) we can
> perhaps add a device tree property indicating that for some boards
> it's OK to turn this rail off. I don't want to add this property
> until I know of a board that needs it.
>
> Fixes: fd968973de95 ("phy: Add driver for rockchip Display Port PHY")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> As far as I know Yakir (the original author) is no longer at Rockchip.
> I've added a few other Rockchip people and hopefully one of them can
> help direct even if they're not directly responsible.
>
> drivers/phy/rockchip/phy-rockchip-dp.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)

Can you help direct this to the right person? ...or should we just
land it and assume it's fine?

-Doug

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