linux-kernel - Re: [PATCH 9/9] phy: qualcomm: m31-eusb2: Make USB repeater optional

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Message-ID: <umoo45pmamr3qraaiommpqh37tgmqidylmtjh3iamlxs34s7wf@ouug53aqvdfd>
Date: Sat, 20 Sep 2025 18:42:18 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Wesley Cheng <wesley.cheng@....qualcomm.com>
Cc: krzk+dt@...nel.org, conor+dt@...nel.org, kishon@...nel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, robh@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-phy@...ts.infradead.org
Subject: Re: [PATCH 9/9] phy: qualcomm: m31-eusb2: Make USB repeater optional

On Fri, Sep 19, 2025 at 08:21:08PM -0700, Wesley Cheng wrote:
> Change the notation of making the USB repeater a required DT parameter.
> Issues were seen when supporting USB2 across different form
> factor/platforms, which led to enumeration issues due to improper eUSB2
> repeater tuning.  By making the repeater optional, for SMB/QC PMIC based
> repeaters, it can utilize repeater settings done in the bootloader,
> which cover a wider range of platforms.

No, please don't depend on the bootloader settings. Instead we need to
implement proper prgramming / tuning for eUSB2 repeaters

> 
> For other repeater vendors outside of the SMB/QC PMICs the repeater
> should be defined and managed within the kernel.
> 
> Signed-off-by: Wesley Cheng <wesley.cheng@....qualcomm.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-m31-eusb2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c b/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
> index f4355d38aad9..b8ddadf78c53 100644
> --- a/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
> +++ b/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
> @@ -285,7 +285,7 @@ static int m31eusb2_phy_probe(struct platform_device *pdev)
>  
>  	phy_set_drvdata(phy->phy, phy);
>  
> -	phy->repeater = devm_of_phy_get_by_index(dev, dev->of_node, 0);
> +	phy->repeater = devm_phy_optional_get(dev, NULL);
>  	if (IS_ERR(phy->repeater))
>  		return dev_err_probe(dev, PTR_ERR(phy->repeater),
>  				     "failed to get repeater\n");

-- 
With best wishes
Dmitry