diff mbox series

[v7,7/8] scsi: ufs-qcom: Delay specific time before gate ref clk

Message ID 1580978008-9327-8-git-send-email-cang@codeaurora.org (mailing list archive)
State New, archived
Headers show
Series None | expand

Commit Message

Can Guo Feb. 6, 2020, 8:33 a.m. UTC 
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@codeaurora.org>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Hongwu Su <hongwus@codeaurora.org>
---
 drivers/scsi/ufs/ufs-qcom.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

Comments

Bjorn Andersson Feb. 6, 2020, 8:33 p.m. UTC | #1 
On Thu 06 Feb 00:33 PST 2020, 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@codeaurora.org>
> Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
> Reviewed-by: Hongwu Su <hongwus@codeaurora.org>
> ---
>  drivers/scsi/ufs/ufs-qcom.c | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> index 85d7c17..39eefa4 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 +847,25 @@ 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) {

Afaict this can't happen, because in patch 6 you check for gating_wait
being 0 and if so set it to 0xff.

> +				udelay(1);
> +			} else {
> +				/*
> +				 * bRefClkGatingWaitTime defines the minimum
> +				 * time for which the reference clock is
> +				 * required by device during transition from
> +				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
> +				 * more time to be on the safe side.
> +				 */
> +				gating_wait += 10;
> +				usleep_range(gating_wait, gating_wait + 10);

I presume there's no strong requirement on the max, so how about using a
substantially larger max - say 1k, or 10k - to allow the usleep_range()
to do it's job?


PS. Please include linux-arm-msm@ on all the patches in the series, not
just two of them.

Regards,
Bjorn

> +			}
> +		}
>  
>  		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
>  
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
Can Guo Feb. 7, 2020, 1:09 a.m. UTC | #2 
On 2020-02-07 04:33, Bjorn Andersson wrote:
> On Thu 06 Feb 00:33 PST 2020, 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@codeaurora.org>
>> Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
>> Reviewed-by: Hongwu Su <hongwus@codeaurora.org>
>> ---
>>  drivers/scsi/ufs/ufs-qcom.c | 22 +++++++++++++++++++---
>>  1 file changed, 19 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> index 85d7c17..39eefa4 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 +847,25 @@ 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) {
> 
> Afaict this can't happen, because in patch 6 you check for gating_wait
> being 0 and if so set it to 0xff.
> 

Sorry, I was intended to give clk_gating_wait_us values only if it is
a UFS3.0 device. I will revise patch 6/8.

>> +				udelay(1);
>> +			} else {
>> +				/*
>> +				 * bRefClkGatingWaitTime defines the minimum
>> +				 * time for which the reference clock is
>> +				 * required by device during transition from
>> +				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
>> +				 * more time to be on the safe side.
>> +				 */
>> +				gating_wait += 10;
>> +				usleep_range(gating_wait, gating_wait + 10);
> 
> I presume there's no strong requirement on the max, so how about using 
> a
> substantially larger max - say 1k, or 10k - to allow the usleep_range()
> to do it's job?
> 
> 
> PS. Please include linux-arm-msm@ on all the patches in the series, not
> just two of them.
> 
> Regards,
> Bjorn
> 

bRefClkGatingWaitTime, as vendor defined in their device attribute is 
usually
around 50~100, 1k or 10k delay makes it too large. usleep_range() works 
well
so long as the delay is within (10us - 20ms), so I added 10 to make sure 
it is
above 10us.

SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
	* Use usleep_range
https://www.kernel.org/doc/Documentation/timers/timers-howto.txt

Thanks,

Can Guo.

>> +			}
>> +		}
>> 
>>  		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
>> 
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
Bjorn Andersson Feb. 7, 2020, 2:10 a.m. UTC | #3 
On Thu 06 Feb 17:09 PST 2020, Can Guo wrote:

> On 2020-02-07 04:33, Bjorn Andersson wrote:
> > On Thu 06 Feb 00:33 PST 2020, 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@codeaurora.org>
> > > Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
> > > Reviewed-by: Hongwu Su <hongwus@codeaurora.org>
> > > ---
> > >  drivers/scsi/ufs/ufs-qcom.c | 22 +++++++++++++++++++---
> > >  1 file changed, 19 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> > > index 85d7c17..39eefa4 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 +847,25 @@ 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) {
> > 
> > Afaict this can't happen, because in patch 6 you check for gating_wait
> > being 0 and if so set it to 0xff.
> > 
> 
> Sorry, I was intended to give clk_gating_wait_us values only if it is
> a UFS3.0 device. I will revise patch 6/8.
> 

Okay, sounds good.

> > > +				udelay(1);
> > > +			} else {
> > > +				/*
> > > +				 * bRefClkGatingWaitTime defines the minimum
> > > +				 * time for which the reference clock is
> > > +				 * required by device during transition from
> > > +				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
> > > +				 * more time to be on the safe side.
> > > +				 */
> > > +				gating_wait += 10;
> > > +				usleep_range(gating_wait, gating_wait + 10);
> > 
> > I presume there's no strong requirement on the max, so how about using a
> > substantially larger max - say 1k, or 10k - to allow the usleep_range()
> > to do it's job?
> > 
> > 
> > PS. Please include linux-arm-msm@ on all the patches in the series, not
> > just two of them.
> > 
> > Regards,
> > Bjorn
> > 
> 
> bRefClkGatingWaitTime, as vendor defined in their device attribute is
> usually
> around 50~100, 1k or 10k delay makes it too large. usleep_range() works well
> so long as the delay is within (10us - 20ms), so I added 10 to make sure it
> is
> above 10us.
> 

I meant specifically the second parameter, i.e:
  usleep_range(bRefClkGatingWaitTime + 10, bRefClkGatingWaitTime + 1000);

As you're not guaranteed an upper bound of this sleep anyway you might
as well give usleep_range() a window of a millisecond (or more) to give
it the flexibility of matching other timer events.

The only drawback with this is that you might "waste" a millisecond.

Regards,
Bjorn

> SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
> 	* Use usleep_range
> https://www.kernel.org/doc/Documentation/timers/timers-howto.txt
> 
> Thanks,
> 
> Can Guo.
> 
> > > +			}
> > > +		}
> > > 
> > >  		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
> > > 
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum,
> > > a Linux Foundation Collaborative Project
Can Guo Feb. 8, 2020, 12:10 a.m. UTC | #4 
On 2020-02-07 10:10, Bjorn Andersson wrote:
> On Thu 06 Feb 17:09 PST 2020, Can Guo wrote:
> 
>> On 2020-02-07 04:33, Bjorn Andersson wrote:
>> > On Thu 06 Feb 00:33 PST 2020, 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@codeaurora.org>
>> > > Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
>> > > Reviewed-by: Hongwu Su <hongwus@codeaurora.org>
>> > > ---
>> > >  drivers/scsi/ufs/ufs-qcom.c | 22 +++++++++++++++++++---
>> > >  1 file changed, 19 insertions(+), 3 deletions(-)
>> > >
>> > > diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> > > index 85d7c17..39eefa4 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 +847,25 @@ 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) {
>> >
>> > Afaict this can't happen, because in patch 6 you check for gating_wait
>> > being 0 and if so set it to 0xff.
>> >
>> 
>> Sorry, I was intended to give clk_gating_wait_us values only if it is
>> a UFS3.0 device. I will revise patch 6/8.
>> 
> 
> Okay, sounds good.
> 
>> > > +				udelay(1);
>> > > +			} else {
>> > > +				/*
>> > > +				 * bRefClkGatingWaitTime defines the minimum
>> > > +				 * time for which the reference clock is
>> > > +				 * required by device during transition from
>> > > +				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
>> > > +				 * more time to be on the safe side.
>> > > +				 */
>> > > +				gating_wait += 10;
>> > > +				usleep_range(gating_wait, gating_wait + 10);
>> >
>> > I presume there's no strong requirement on the max, so how about using a
>> > substantially larger max - say 1k, or 10k - to allow the usleep_range()
>> > to do it's job?
>> >
>> >
>> > PS. Please include linux-arm-msm@ on all the patches in the series, not
>> > just two of them.
>> >
>> > Regards,
>> > Bjorn
>> >
>> 
>> bRefClkGatingWaitTime, as vendor defined in their device attribute is
>> usually
>> around 50~100, 1k or 10k delay makes it too large. usleep_range() 
>> works well
>> so long as the delay is within (10us - 20ms), so I added 10 to make 
>> sure it
>> is
>> above 10us.
>> 
> 
> I meant specifically the second parameter, i.e:
>   usleep_range(bRefClkGatingWaitTime + 10, bRefClkGatingWaitTime + 
> 1000);
> 
> As you're not guaranteed an upper bound of this sleep anyway you might
> as well give usleep_range() a window of a millisecond (or more) to give
> it the flexibility of matching other timer events.
> 
> The only drawback with this is that you might "waste" a millisecond.
> 
> Regards,
> Bjorn
> 

Hi Bjorn,

Device ref clk gate/ungate can happen very frequently if clk gating is
enabled. The "wasted" milliseconds might be accumulated to affect
read/write latency, i.e:

If read/write requests come, clk ungate kicks start, it flushes ongoing
gate work if any, if we "waste" a millisecond here, the read/write
requests will be delayed a millisecond. I am not sure how much it may
impact the overall performance in a long term test.

Thanks,

Can Guo.

>> SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
>> 	* Use usleep_range
>> https://www.kernel.org/doc/Documentation/timers/timers-howto.txt
>> 
>> Thanks,
>> 
>> Can Guo.
>> 
>> > > +			}
>> > > +		}
>> > >
>> > >  		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
>> > >
>> > > --
>> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> > > Forum,
>> > > a Linux Foundation Collaborative Project
diff mbox series

Patch

diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
index 85d7c17..39eefa4 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 +847,25 @@  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 {
+				/*
+				 * bRefClkGatingWaitTime defines the minimum
+				 * time for which the reference clock is
+				 * required by device during transition from
+				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
+				 * more time to be on the safe side.
+				 */
+				gating_wait += 10;
+				usleep_range(gating_wait, gating_wait + 10);
+			}
+		}
 
 		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);