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

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To: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>

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

From: Wesley Cheng <wesley.cheng@xxxxxxxxxxxxxxxx>

Date: 2025年9月22日 18:03:54 -0700

Cc: krzk+dt@xxxxxxxxxx, conor+dt@xxxxxxxxxx, kishon@xxxxxxxxxx, vkoul@xxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, robh@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-arm-msm@xxxxxxxxxxxxxxx, devicetree@xxxxxxxxxxxxxxx, linux-usb@xxxxxxxxxxxxxxx, linux-phy@xxxxxxxxxxxxxxxxxxx

In-reply-to: <umoo45pmamr3qraaiommpqh37tgmqidylmtjh3iamlxs34s7wf@ouug53aqvdfd>

References: <20250920032108.242643-1-wesley.cheng@oss.qualcomm.com> <20250920032108.242643-10-wesley.cheng@oss.qualcomm.com> <umoo45pmamr3qraaiommpqh37tgmqidylmtjh3iamlxs34s7wf@ouug53aqvdfd>

User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1

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@xxxxxxxxxxxxxxxx>
---
 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");

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