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Message-ID: <a7296997-89a1-2fb6-3bb4-1fc60d50a132@acm.org>
Date:   Fri, 19 May 2023 15:16:07 -0700
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Subject: Re: [PATCH v2] ufs: poll HCS.UCRDY before issuing a UIC command
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To:     Kiwoong Kim <kwmad.kim@samsung.com>, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, alim.akhtar@samsung.com,
        avri.altman@wdc.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com, beanhuo@micron.com,
        adrian.hunter@intel.com, sc.suh@samsung.com, hy50.seo@samsung.com,
        sh425.lee@samsung.com, kwangwon.min@samsung.com
References: <CGME20230516034218epcas2p297e9c5a33d370c8c45a40ab58f500ae0@epcas2p2.samsung.com>
 <1684208012-114324-1-git-send-email-kwmad.kim@samsung.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <1684208012-114324-1-git-send-email-kwmad.kim@samsung.com>
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On 5/15/23 20:33, Kiwoong Kim wrote:
> v1 -> v2: replace usleep_range with udelay
> because it's a sleepable period.
> 
> With auto hibern8 enabled, UIC could be working
> for a while to process a hibern8 operation and HCI
> reports UIC not ready for a short term through HCS.UCRDY.
> And UFS driver can't recognize the operation.
> UFSHCI spec specifies UCRDY like this:
> whether the host controller is ready to process UIC COMMAND
> 
> The 'ready' could be seen as many different meanings. If the meaning
> includes not processing any request from HCI, processing a hibern8
> operation can be 'not ready'. In this situation, the driver needs to
> wait until the operations is completed.
> 
> Signed-off-by: Kiwoong Kim <kwmad.kim@samsung.com>
> ---
>   drivers/ufs/core/ufshcd.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 9434328..5f6819a 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2365,7 +2365,18 @@ static inline int ufshcd_hba_capabilities(struct ufs_hba *hba)
>    */
>   static inline bool ufshcd_ready_for_uic_cmd(struct ufs_hba *hba)
>   {
> -	return ufshcd_readl(hba, REG_CONTROLLER_STATUS) & UIC_COMMAND_READY;
> +	ktime_t timeout = ktime_add_ms(ktime_get(), UIC_CMD_TIMEOUT);
> +	u32 val = 0;
> +
> +	do {
> +		val = ufshcd_readl(hba, REG_CONTROLLER_STATUS) &
> +			UIC_COMMAND_READY;
> +		if (val)
> +			break;
> +		udelay(500);
> +	} while (ktime_before(ktime_get(), timeout));
> +
> +	return val ? true : false;
>   }

Sleeping during up to 500 ms while holding a spin lock is not acceptable.
Has it been considered to modify the UFS core such that the host_lock is
not held around calls of the above function, e.g. via the (untested) patch
below?

Thanks,

Bart.


diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 9736b2b4120e..394283b04d7c 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -2416,7 +2416,6 @@ __ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd,
  		      bool completion)
  {
  	lockdep_assert_held(&hba->uic_cmd_mutex);
-	lockdep_assert_held(hba->host->host_lock);

  	if (!ufshcd_ready_for_uic_cmd(hba)) {
  		dev_err(hba->dev,
@@ -2452,9 +2451,7 @@ int ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd)
  	mutex_lock(&hba->uic_cmd_mutex);
  	ufshcd_add_delay_before_dme_cmd(hba);

-	spin_lock_irqsave(hba->host->host_lock, flags);
  	ret = __ufshcd_send_uic_cmd(hba, uic_cmd, true);
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
  	if (!ret)
  		ret = ufshcd_wait_for_uic_cmd(hba, uic_cmd);

@@ -4122,8 +4119,8 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba *hba, struct uic_command *cmd)
  		wmb();
  		reenable_intr = true;
  	}
-	ret = __ufshcd_send_uic_cmd(hba, cmd, false);
  	spin_unlock_irqrestore(hba->host->host_lock, flags);
+	ret = __ufshcd_send_uic_cmd(hba, cmd, false);
  	if (ret) {
  		dev_err(hba->dev,
  			"pwr ctrl cmd 0x%x with mode 0x%x uic error %d\n",