phy: qcom-qmp-pcie: replace power-down delay

phy: qcom-qmp-pcie: replace power-down delay

[ Upstream commit 51bd33069f80705aba5f4725287bc5688ca6d92a ]

The power-down delay was included in the first version of the QMP driver
as an optional delay after powering on the PHY (using
POWER_DOWN_CONTROL) and just before starting it. Later changes modified
this sequence by powering on before initialising the PHY, but the
optional delay stayed where it was (i.e. before starting the PHY).

The vendor driver does not use a delay before starting the PHY and this
is likely not needed on any platform unless there is a corresponding
delay in the vendor kernel init sequence tables (i.e. in devicetree).

But as the vendor kernel do have a 1 ms delay *after* starting the PHY
and before starting to poll the status it is possible that later
contributors have simply not noticed that the mainline power-down delay
is not equivalent.

As the current delay before even starting the PHY is pretty much
pointless and likely a mistake, move the delay after starting the PHY
which avoids a few iterations of polling and speeds up startup by 1 ms
(the poll loop otherwise takes about 1.8 ms).

Note that MSM8998 has never used a power-down delay so add a flag to
skip the delay in case starting the PHY is faster on MSM8998. This can
be removed after someone takes a measurement.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20221012081241.18273-10-johan+linaro@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Stable-dep-of: 4a9eac5ae220 ("phy: qcom-qmp-pcie: fix sc8180x initialisation")
Signed-off-by: Sasha Levin <sashal@kernel.org>