linux-kernel - Re: [PATCH] phy: qcom-snps-femto-v2: Add load and voltage setting for LDO's used

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Date: Tue, 7 May 2024 14:55:45 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Udipto Goswami <quic_ugoswami@...cinc.com>, Bjorn Andersson <andersson@...nel.org>, 
	Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phy: qcom-snps-femto-v2: Add load and voltage setting for
 LDO's used

On Tue, 7 May 2024 at 14:43, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>
>
>
> On 5/2/24 15:12, Dmitry Baryshkov wrote:
> > On Thu, 2 May 2024 at 15:33, Udipto Goswami <quic_ugoswami@...cinc.com> wrote:
> >>
> >> The Femto phy depends on 0.88/ 1.8/ 3.3V regulators for its operation.
> >> If one of the regulators is not voted to the required minimum voltage
> >> for phy to operate, then High speed mode of operation will fail.
> >>
> >> On certain targets like (qcm6490_rb3gen2) where the minimum voltage
> >> of the regulator is lower than the operating voltage of the phy.
> >> If not voted properly, the phy supply would be limited to the min value
> >> of the LDO thereby rendering the phy non-operational.
> >>
> >> The current implementation of the regulators in the Femto PHY is not
> >> setting the load and voltage for each LDO. The appropriate voltages and
> >> loads required for the PHY to operate should be set.
> >
> > Please move min/max voltages to the DTS. There is no need to set them
> > from the driver.
> >
> > Also, is there any reason why you can't use `regulator-initial-mode =
> > <RPMH_REGULATOR_MODE_HPM>;` like other boards do?
>
> The point is to aggregate the values and switch to HPM if a threshold is
> crossed (or stay in LPM otherwise)

I see that other boards use regulator-initial-mode for the USB PHY
regulators. Are we going to change all of them too?
Also note, that while the combo QMP driver sets the loads, the pure
USB QMP PHY driver doesn't set the loads. This way we can end up with
the undervolted PHY.

-- 
With best wishes
Dmitry