linux-kernel - Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

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Message-ID: <20250422124546.GB896279-robh@kernel.org>
Date: Tue, 22 Apr 2025 07:45:46 -0500
From: Rob Herring <robh@...nel.org>
To: Nitin Rawat <quic_nitirawa@...cinc.com>
Cc: alim.akhtar@...sung.com, avri.altman@....com, bvanassche@....org,
	krzk+dt@...nel.org, mani@...nel.org, conor+dt@...nel.org,
	James.Bottomley@...senpartnership.com, martin.petersen@...cle.com,
	beanhuo@...ron.com, peter.wang@...iatek.com,
	linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM
 Feature

On Thu, Apr 17, 2025 at 06:16:45PM +0530, Nitin Rawat wrote:
> There are emulation FPGA platforms or other platforms where UFS low
> power mode is either unsupported or power efficiency is not a critical
> requirement.
> 
> Disable all low power mode UFS feature based on the "disable-lpm" device
> tree property parsed in platform driver.
> 
> Signed-off-by: Nitin Rawat <quic_nitirawa@...cinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index 1b37449fbffc..1024edf36b68 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)
> 
>  static void ufs_qcom_set_caps(struct ufs_hba *hba)
>  {
> -	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> -	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> -	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> -	hba->caps |= UFSHCD_CAP_WB_EN;
> -	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> -	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> -
> +	if (!hba->disable_lpm) {
> +		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> +		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> +		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> +		hba->caps |= UFSHCD_CAP_WB_EN;
> +		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> +		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> +	}

Doesn't RuntimePM already have userspace controls? And that's a Linux 
feature that shouldn't really be controlled by DT. I think this property 
should still to things defined by the UFS spec.

Rob