Re: [PATCH v1 2/2] scsi: ufs: Try to save power mode change and UIC cmd completion timeout

[Stanley Chu]

Hi Can,

On Tue, 2020-11-03 at 16:01 +0800, Can Guo wrote:
> Hi Stanley,
> 
> On 2020-11-03 15:20, Stanley Chu wrote:
> > Hi Can,
> > 
> > Except for below nit, otherwise looks good to me.
> > 
> > Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> > 
> > On Mon, 2020-11-02 at 22:24 -0800, Can Guo wrote:
> >> Use the uic_cmd->cmd_active as a flag to track the lifecycle of an UIC 
> >> cmd.
> >> The flag is set before send the UIC cmd and cleared in IRQ handler. 
> >> When a
> >> PMC or UIC cmd completion timeout happens, if the flag is not set, 
> >> instead
> >> of returning timeout error, we still treat it as a successful 
> >> operation.
> >> This is to deal with the scenario in which completion has been raised 
> >> but
> >> the one waiting for the completion cannot be awaken in time due to 
> >> kernel
> >> scheduling problem.
> >> 
> >> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> >> ---
> >>  drivers/scsi/ufs/ufshcd.c | 26 ++++++++++++++++++++++++--
> >>  drivers/scsi/ufs/ufshcd.h |  2 ++
> >>  2 files changed, 26 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> >> index efa7d86..7f33310 100644
> >> --- a/drivers/scsi/ufs/ufshcd.c
> >> +++ b/drivers/scsi/ufs/ufshcd.c
> >> @@ -2122,10 +2122,20 @@ ufshcd_wait_for_uic_cmd(struct ufs_hba *hba, 
> >> struct uic_command *uic_cmd)
> >>  	unsigned long flags;
> >> 
> >>  	if (wait_for_completion_timeout(&uic_cmd->done,
> >> -					msecs_to_jiffies(UIC_CMD_TIMEOUT)))
> >> +					msecs_to_jiffies(UIC_CMD_TIMEOUT))) {
> >>  		ret = uic_cmd->argument2 & MASK_UIC_COMMAND_RESULT;
> >> -	else
> >> +	} else {
> >>  		ret = -ETIMEDOUT;
> >> +		dev_err(hba->dev,
> >> +			"uic cmd 0x%x with arg3 0x%x completion timeout\n",
> >> +			uic_cmd->command, uic_cmd->argument3);
> >> +
> >> +		if (!uic_cmd->cmd_active) {
> >> +			dev_err(hba->dev, "%s: UIC cmd has been completed, return the 
> >> result\n",
> >> +				__func__);
> >> +			ret = uic_cmd->argument2 & MASK_UIC_COMMAND_RESULT;
> >> +		}
> >> +	}
> >> 
> >>  	spin_lock_irqsave(hba->host->host_lock, flags);
> >>  	hba->active_uic_cmd = NULL;
> >> @@ -2157,6 +2167,7 @@ __ufshcd_send_uic_cmd(struct ufs_hba *hba, 
> >> struct uic_command *uic_cmd,
> >>  	if (completion)
> >>  		init_completion(&uic_cmd->done);
> >> 
> >> +	uic_cmd->cmd_active = 1;
> >>  	ufshcd_dispatch_uic_cmd(hba, uic_cmd);
> >> 
> >>  	return 0;
> >> @@ -3828,10 +3839,18 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba 
> >> *hba, struct uic_command *cmd)
> >>  		dev_err(hba->dev,
> >>  			"pwr ctrl cmd 0x%x with mode 0x%x completion timeout\n",
> >>  			cmd->command, cmd->argument3);
> >> +
> >> +		if (!cmd->cmd_active) {
> >> +			dev_err(hba->dev, "%s: Power Mode Change operation has been 
> >> completed, go check UPMCRS\n",
> >> +				__func__);
> >> +			goto check_upmcrs;
> >> +		}
> >> +
> >>  		ret = -ETIMEDOUT;
> >>  		goto out;
> >>  	}
> >> 
> >> +check_upmcrs:
> >>  	status = ufshcd_get_upmcrs(hba);
> >>  	if (status != PWR_LOCAL) {
> >>  		dev_err(hba->dev,
> >> @@ -4923,11 +4942,14 @@ static irqreturn_t ufshcd_uic_cmd_compl(struct 
> >> ufs_hba *hba, u32 intr_status)
> >>  			ufshcd_get_uic_cmd_result(hba);
> >>  		hba->active_uic_cmd->argument3 =
> >>  			ufshcd_get_dme_attr_val(hba);
> >> +		if (!hba->uic_async_done)
> > 
> > Is this check necessary?
> > 
> 
> Thanks for your quick response.
> 
> In the case of PMC, UIC cmd completion IRQ comes first, then power
> status change IRQ comes next. In this case, an UIC cmd's lifecyle
> ends only after the power status change IRQ comes [1].
> 
> I guess you may want to say that in current code since we have
> masked UIC cmd completion IRQ in the case of a PMC operation, so
> no need to check it here since we won't be here anyways before
> power status change IRQ comes. So, removing the check here
> definitely works, and then we won't even need below line as well.
> 

You read my mind : )

> 	if ((intr_status & UFSHCD_UIC_PWR_MASK) && hba->uic_async_done) {
> +		hba->active_uic_cmd->cmd_active = 0;
> 		complete(hba->uic_async_done);
> 		retval = IRQ_HANDLED;
> 
> If my guess is right, my opinion is that the current change may
> be more readable and comprehensive as it strictly follows my
> description in [1]. What do you think?

Both looks fine to me.

Thanks for the detailed description.

Stanley Chu

> 
> Thanks,
> 
> Can Guo.
> 
> >> +			hba->active_uic_cmd->cmd_active = 0;
> >>  		complete(&hba->active_uic_cmd->done);
> >>  		retval = IRQ_HANDLED;
> >>  	}
> >> 
> >>  	if ((intr_status & UFSHCD_UIC_PWR_MASK) && hba->uic_async_done) {
> >> +		hba->active_uic_cmd->cmd_active = 0;
> >>  		complete(hba->uic_async_done);
> >>  		retval = IRQ_HANDLED;
> >>  	}
> >> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> >> index 66e5338..be982ed 100644
> >> --- a/drivers/scsi/ufs/ufshcd.h
> >> +++ b/drivers/scsi/ufs/ufshcd.h
> >> @@ -64,6 +64,7 @@ enum dev_cmd_type {
> >>   * @argument1: UIC command argument 1
> >>   * @argument2: UIC command argument 2
> >>   * @argument3: UIC command argument 3
> >> + * @cmd_active: Indicate if UIC command is outstanding
> >>   * @done: UIC command completion
> >>   */
> >>  struct uic_command {
> >> @@ -71,6 +72,7 @@ struct uic_command {
> >>  	u32 argument1;
> >>  	u32 argument2;
> >>  	u32 argument3;
> >> +	int cmd_active;
> >>  	struct completion done;
> >>  };
> >> 
> > 
> > 
> > 
> > Thanks,
> > Stanley Chu