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 15:41:38 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...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 5/7/24 13:55, Dmitry Baryshkov wrote:
> 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?

Not sure about initial mode yet.

> 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.

Sounds like something to fix, then

Konrad