linux-kernel - Re: [PATCH v4 7/8] scsi: ufs-qcom: Delay specific time before gate ref clk

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Date:   Fri, 24 Jan 2020 10:04:10 -0800
From:   "Asutosh Das (asd)" <asutoshd@...eaurora.org>
To:     Can Guo <cang@...eaurora.org>, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com
Cc:     Andy Gross <agross@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/8] scsi: ufs-qcom: Delay specific time before gate
 ref clk

On 1/22/2020 11:25 PM, Can Guo wrote:
> After enter hibern8, as UFS JEDEC ver 3.0 requires, a specific gating wait
> time is required before disable the device reference clock. If it is not
> specified, use the old delay.
> 
> Signed-off-by: Can Guo <cang@...eaurora.org>
> ---

Reviewed-by: Asutosh Das <asutoshd@...eaurora.org>

>   drivers/scsi/ufs/ufs-qcom.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> index 85d7c17..3b5b2d9 100644
> --- a/drivers/scsi/ufs/ufs-qcom.c
> +++ b/drivers/scsi/ufs/ufs-qcom.c
> @@ -833,6 +833,8 @@ static int ufs_qcom_bus_register(struct ufs_qcom_host *host)
>   
>   static void ufs_qcom_dev_ref_clk_ctrl(struct ufs_qcom_host *host, bool enable)
>   {
> +	unsigned long gating_wait;
> +
>   	if (host->dev_ref_clk_ctrl_mmio &&
>   	    (enable ^ host->is_dev_ref_clk_enabled)) {
>   		u32 temp = readl_relaxed(host->dev_ref_clk_ctrl_mmio);
> @@ -845,11 +847,16 @@ static void ufs_qcom_dev_ref_clk_ctrl(struct ufs_qcom_host *host, bool enable)
>   		/*
>   		 * If we are here to disable this clock it might be immediately
>   		 * after entering into hibern8 in which case we need to make
> -		 * sure that device ref_clk is active at least 1us after the
> +		 * sure that device ref_clk is active for specific time after
>   		 * hibern8 enter.
>   		 */
> -		if (!enable)
> -			udelay(1);
> +		if (!enable) {
> +			gating_wait = host->hba->dev_info.clk_gating_wait_us;
> +			if (!gating_wait)
> +				udelay(1);
> +			else
> +				usleep_range(gating_wait, gating_wait + 10);
> +		}
>   
>   		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
>   
> 


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