linux-kernel - RE: [PATCH v1] scsi: ufs: remove clk_scaling

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Message-ID: <DM6PR04MB657519E60FAFA19434531CE2FC2B9@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Sun, 6 Feb 2022 08:20:58 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Kiwoong Kim <kwmad.kim@...sung.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "sc.suh@...sung.com" <sc.suh@...sung.com>,
        "hy50.seo@...sung.com" <hy50.seo@...sung.com>,
        "sh425.lee@...sung.com" <sh425.lee@...sung.com>,
        "bhoon95.kim@...sung.com" <bhoon95.kim@...sung.com>,
        "vkumar.1997@...sung.com" <vkumar.1997@...sung.com>
Subject: RE: [PATCH v1] scsi: ufs: remove clk_scaling_lock when clkscaling
 isn't supported.

 
> clk_scaling_lock is to prevent from running clkscaling related operations
> with others which might be affected by the operations concurrently.
> I think it looks hardware specific.
> If the feature isn't supported, I think there is no reasonto prevent from
                                                                                         ^^^ reason to 

> running other functions, such as ufshcd_queuecommand and
It is no longer used in queuecommand since 5675c381ea51 and 8d077ede48c1

> ufshcd_exec_dev_cmd, concurrently.
> 
> So I add a condition at some points protecting with clk_scaling_lock.
But you still need a way to serialize device management commands.

Thanks,
Avri

> 
> Signed-off-by: Kiwoong Kim <kwmad.kim@...sung.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 460d2b4..8471c90 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2980,7 +2980,8 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
>         /* Protects use of hba->reserved_slot. */
>         lockdep_assert_held(&hba->dev_cmd.lock);
> 
> -       down_read(&hba->clk_scaling_lock);
> +       if (ufshcd_is_clkscaling_supported(hba))
> +               down_read(&hba->clk_scaling_lock);
> 
>         lrbp = &hba->lrb[tag];
>         WARN_ON(lrbp->cmd);
> @@ -2998,7 +2999,8 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
>                                     (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
> 
>  out:
> -       up_read(&hba->clk_scaling_lock);
> +       if (ufshcd_is_clkscaling_supported(hba))
> +               up_read(&hba->clk_scaling_lock);
>         return err;
>  }
> 
> @@ -6014,7 +6016,8 @@ static void ufshcd_err_handling_prepare(struct
> ufs_hba *hba)
>                 if (ufshcd_is_clkscaling_supported(hba) &&
>                     hba->clk_scaling.is_enabled)
>                         ufshcd_suspend_clkscaling(hba);
> -               ufshcd_clk_scaling_allow(hba, false);
> +               if (ufshcd_is_clkscaling_supported(hba))
> +                       ufshcd_clk_scaling_allow(hba, false);
>         }
>         ufshcd_scsi_block_requests(hba);
>         /* Drain ufshcd_queuecommand() */
> @@ -6247,7 +6250,8 @@ static void ufshcd_err_handler(struct work_struct
> *work)
>                  * Hold the scaling lock just in case dev cmds
>                  * are sent via bsg and/or sysfs.
>                  */
> -               down_write(&hba->clk_scaling_lock);
> +               if (ufshcd_is_clkscaling_supported(hba))
> +                       down_write(&hba->clk_scaling_lock);
>                 hba->force_pmc = true;
>                 pmc_err = ufshcd_config_pwr_mode(hba, &(hba->pwr_info));
>                 if (pmc_err) {
> @@ -6257,7 +6261,8 @@ static void ufshcd_err_handler(struct work_struct
> *work)
>                 }
>                 hba->force_pmc = false;
>                 ufshcd_print_pwr_info(hba);
> -               up_write(&hba->clk_scaling_lock);
> +               if (ufshcd_is_clkscaling_supported(hba))
> +                       up_write(&hba->clk_scaling_lock);
>                 spin_lock_irqsave(hba->host->host_lock, flags);
>         }
> 
> @@ -6753,7 +6758,8 @@ static int ufshcd_issue_devman_upiu_cmd(struct
> ufs_hba *hba,
>         /* Protects use of hba->reserved_slot. */
>         lockdep_assert_held(&hba->dev_cmd.lock);
> 
> -       down_read(&hba->clk_scaling_lock);
> +       if (ufshcd_is_clkscaling_supported(hba))
> +               down_read(&hba->clk_scaling_lock);
> 
>         lrbp = &hba->lrb[tag];
>         WARN_ON(lrbp->cmd);
> @@ -6822,7 +6828,8 @@ static int ufshcd_issue_devman_upiu_cmd(struct
> ufs_hba *hba,
>         ufshcd_add_query_upiu_trace(hba, err ? UFS_QUERY_ERR :
> UFS_QUERY_COMP,
>                                     (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
> 
> -       up_read(&hba->clk_scaling_lock);
> +       if (ufshcd_is_clkscaling_supported(hba))
> +               up_read(&hba->clk_scaling_lock);
>         return err;
>  }
> 
> --
> 2.7.4