linux-kernel - Re: [PATCH v2 12/15] phy: qcom-qmp-pcie: fix initialisation reset

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Message-ID: <02a879d4-cc7a-ca8e-7334-755873baa3e7@linaro.org>
Date:   Wed, 19 Oct 2022 16:52:29 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Johan Hovold <johan+linaro@...nel.org>,
        Vinod Koul <vkoul@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/15] phy: qcom-qmp-pcie: fix initialisation reset

On 19/10/2022 14:35, Johan Hovold wrote:
> Add the missing delay after asserting reset. This is specifically needed
> for the reset to have any effect on SC8280XP.
> 
> The vendor driver uses a 1 ms delay, but that seems a bit excessive.
> Instead use a 200 us delay which appears to be more than enough and also
> matches the UFS reset delay added by commit 870b1279c7a0 ("scsi:
> ufs-qcom: Add reset control support for host controller").
> 
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index 2f4bdef73395..9c8e009033f1 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -1866,6 +1866,8 @@ static int qmp_pcie_init(struct phy *phy)
>   		goto err_disable_regulators;
>   	}
>   
> +	usleep_range(200, 300);
> +

If there is a v3, I'd kindly ask to add a comment about vendor using 1ms 
here.

>   	ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
>   	if (ret) {
>   		dev_err(qmp->dev, "reset deassert failed\n");

-- 
With best wishes
Dmitry