Re: [PATCH v2 09/14] phy: qcom-qmp-pcie: replace power-down delay

[Dmitry Baryshkov]

On 12/10/2022 11:12, Johan Hovold wrote:
> 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@xxxxxxxxxx>
> ---
>   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 33 +++++-------------------
>   1 file changed, 6 insertions(+), 27 deletions(-)
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>

--
With best wishes
Dmitry