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

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Message-ID: <95c59ba6-fd9c-ef59-c5c5-33cb2fb5db8e@oss.qualcomm.com>
Date: Mon, 22 Sep 2025 18:03:54 -0700
From: Wesley Cheng <wesley.cheng@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....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 9/20/2025 8:42 AM, Dmitry Baryshkov wrote:
> 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
> 

Hi Dmitry,

Will update the next rev with the entries to support the SM2370 repeater.

Thanks
Wesley Cheng

>>
>> 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");
>