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

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Message-ID: <vbuo2yel2pdcwnmz32f4t5pb6v3ptt2bcs2t6ybab2jxnkd6e7@rjnsbawj4zpb>
Date: Thu, 28 Nov 2024 10:43:45 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: 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 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.

For this reason we're not doing any load requests today. Can you confirm
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
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>
> 
>