linux-kernel - Re: [PATCH v2] phy: qcom-qusb2: Add regulator_set

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Message-ID: <18e40154-f4ea-4100-9f4f-9c9aa5e251d7@quicinc.com>
Date: Fri, 29 Nov 2024 18:26:30 +0800
From: Tingwei Zhang <quic_tingweiz@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>,
        Song Xue
	<quic_songxue@...cinc.com>
CC: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
        Manu Gautam <mgautam@...eaurora.org>,
        Vivek Gautam
	<vivek.gautam@...eaurora.org>, <kernel@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] phy: qcom-qusb2: Add regulator_set_load to Qualcomm
 usb phy

On 11/29/2024 12:43 AM, Bjorn Andersson wrote:
> On Thu, Nov 21, 2024 at 04:09:27PM +0800, Song Xue wrote:
>> Set the current load before enable regulator supplies at QUSB phy.
>>
>> Encountered one issue where the board powered down instantly once the UVC
>> camera was attached to USB port while adding host mode on usb port and
>> testing a UVC camera with the driver on QCS615 platform. The extensible
>> boot loader mentioned that OCP(Over Current Protection) occurred at LDO12
>> from regulators-0 upon powered on board again. That indicates that the
>> current load set for QUSB phy, which use the regulator supply, is lower
>> than expected.
>>
>> As per QUSB spec, set the maximum current load at 30mA to avoid overcurrent
>> load when attach a device to the USB port.
>>
>> Fixes: 937e17f36a32 ("phy: qcom-qusb2: Power-on PHY before initialization")
>> Signed-off-by: Song Xue <quic_songxue@...cinc.com>
> 
> The patch looks good. But if we describe the regulator(s) with
> regulator-allow-set-load; and not all the consumers vote for load, the
> sum of the load when USB phy is disabled goes to 0 and we will enter
> LPM.

That's exactly the issue we encountered on QCS615 ride. Qualcomm UFS 
driver sets load while USB phy doesn't set load. That's the reason we 
raised this patch.
> 
> For this reason we're not doing any load requests today. Can you confirm

When I grep regulator_set_load in Kernel, there are 27 hits in drivers. 
You are correct, it will trigger issue when some consumers set load 
while some don't.
However, how can we prevent other drivers outside of Qualcomm to use 
regulator_set_load? It will trigger the same issue.
Is there something we can do in regulator driver to prevent this issue? 
If consumer doesn't set load, regulator works in HPM even another 
consumer set load to 0?

> that this works fine with a dtb where only HPM is permitted (as well as
> LPM and HPM)? If so I'd be in favor of us merging this change, but

Do you mean test with HPM only regulator and regulator which allows to 
be set to HPM and LPM?

> keeping the dts HPM-only until someone confirms that all consumers of
> these regulators specify load-votes.
> 
> Regards,
> Bjorn
> 
>> ---
>> Changes in v2:
>> - Removed "---" above the Fixes.
>> - Link to v1: https://lore.kernel.org/r/20241121-add_set_load_to_qusb_phy-v1-1-0f44f3a3290e@quicinc.com
>> ---
>>   drivers/phy/qualcomm/phy-qcom-qusb2.c | 13 ++++++++++++-
>>   1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/phy/qualcomm/phy-qcom-qusb2.c b/drivers/phy/qualcomm/phy-qcom-qusb2.c
>> index c52655a383cef008552ed4533b9f31d1cbf34a13..80f0d17c42717e843937255a9a780bbae5998535 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-qusb2.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-qusb2.c
>> @@ -722,16 +722,27 @@ static int __maybe_unused qusb2_phy_runtime_resume(struct device *dev)
>>   	return ret;
>>   }
>>   
>> +#define QUSB2PHY_HPM_LOAD 30000 /*uA*/
>> +
>>   static int qusb2_phy_init(struct phy *phy)
>>   {
>>   	struct qusb2_phy *qphy = phy_get_drvdata(phy);
>>   	const struct qusb2_phy_cfg *cfg = qphy->cfg;
>>   	unsigned int val = 0;
>>   	unsigned int clk_scheme;
>> -	int ret;
>> +	int ret, i;
>>   
>>   	dev_vdbg(&phy->dev, "%s(): Initializing QUSB2 phy\n", __func__);
>>   
>> +	/* set the current load */
>> +	for (i = 0; i < ARRAY_SIZE(qphy->vregs); i++) {
>> +		ret = regulator_set_load(qphy->vregs[i].consumer, QUSB2PHY_HPM_LOAD);
>> +		if (ret) {
>> +			dev_err(&phy->dev, "failed to set load at %s\n", qphy->vregs[i].supply);
>> +			return ret;
>> +		}
>> +	}
>> +
>>   	/* turn on regulator supplies */
>>   	ret = regulator_bulk_enable(ARRAY_SIZE(qphy->vregs), qphy->vregs);
>>   	if (ret)
>>
>> ---
>> base-commit: decc701f41d07481893fdea942c0ac6b226e84cd
>> change-id: 20241121-add_set_load_to_qusb_phy-d1327c797ffe
>>
>> Best regards,
>> -- 
>> Song Xue <quic_songxue@...cinc.com>
>>
>>


-- 
Thanks,
Tingwei