linux-kernel - Re: [PATCH 10/13] phy: qcom-qmp-combo: drop sc8280xp power-down delay

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Message-ID: <Y0V70n11uaztrYHo@hovoldconsulting.com>
Date:   Tue, 11 Oct 2022 16:21:06 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/13] phy: qcom-qmp-combo: drop sc8280xp power-down delay

On Tue, Oct 11, 2022 at 05:07:16PM +0300, Dmitry Baryshkov wrote:
> On 11/10/2022 16:14, Johan Hovold wrote:
> > The SC8280XP combo PHY does not need a delay before starting the USB PHY
> > (which is what the has_pwrdn_delay config option really controls) so
> > drop the unnecessary delay.
> > 
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > ---
> >   drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 4 ----
> >   1 file changed, 4 deletions(-)
> 
> Just an obvious question: 'does not need a delay' comes from your 
> experience or from some vendor flag (in ACPI/DT/kernel/wherever)?

There's no corresponding delay in the vendor driver; the delay as it
is used in the driver (before starting the PHY) makes no sense and
shouldn't be used for new platforms; and I've verified that it isn't
needed on SC8280XP.

I'm confident that this was just another case of copy-pasting. And the
buck stops here (with SC8280XP). ;)

Johan