[PATCH 0/4] Prepare for upstreaming Pixel 6 UFS support

[PATCH 0/4] Prepare for upstreaming Pixel 6 UFS support

[Bart Van Assche]

Hi Martin,

The UFS controller in the Google Pixel 6 phone requires that SCSI command
processing is suspended while reprogramming encryption keys. The patches in
this series are a first step towards integrating support in the upstream
kernel for the UFS controller in the Pixel 6. Please consider these patches
for inclusion in kernel v5.19.

Note: instructions for downloading the Pixel 6 source code are available at
https://source.android.com/setup/build/building-kernels.

Thanks,

Bart.

Bart Van Assche (4):
  scsi: ufs: Reduce the clock scaling latency
  scsi: ufs: Move a clock scaling check
  scsi: ufs: Pass the clock scaling timeout as an argument
  scsi: ufs: Add suspend/resume SCSI command processing support

 drivers/scsi/ufs/ufshcd.c | 50 ++++++++++++++++++++++++++++++++++-----
 drivers/scsi/ufs/ufshcd.h |  3 +++
 2 files changed, 47 insertions(+), 6 deletions(-)

[PATCH 1/4] scsi: ufs: Reduce the clock scaling latency

[Bart Van Assche]

Wait at most 20 ms before rechecking the doorbells instead of waiting
for a potentially long time between doorbell checks.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 2b4390a1106e..a3fecbb403d3 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1141,7 +1141,7 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 		}
 
 		spin_unlock_irqrestore(hba->host->host_lock, flags);
-		schedule();
+		io_schedule_timeout(msecs_to_jiffies(20));
 		if (ktime_to_us(ktime_sub(ktime_get(), start)) >
 		    wait_timeout_us) {
 			timeout = true;

RE: [PATCH 1/4] scsi: ufs: Reduce the clock scaling latency

[Avri Altman]

> Wait at most 20 ms before rechecking the doorbells instead of waiting
> for a potentially long time between doorbell checks.
> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Avri Altman <avri.altman@wdc.com>

Nit:
An upper bound of 20msec seems reasonable.
Maybe we should create some linkage to DOORBELL_CLR_TOUT_US?
> ---
>  drivers/scsi/ufs/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 2b4390a1106e..a3fecbb403d3 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1141,7 +1141,7 @@ static int ufshcd_wait_for_doorbell_clr(struct
> ufs_hba *hba,
>                 }
> 
>                 spin_unlock_irqrestore(hba->host->host_lock, flags);
> -               schedule();
> +               io_schedule_timeout(msecs_to_jiffies(20));
>                 if (ktime_to_us(ktime_sub(ktime_get(), start)) >
>                     wait_timeout_us) {
>                         timeout = true;

Re: [PATCH 1/4] scsi: ufs: Reduce the clock scaling latency

[Bart Van Assche]

On 4/28/22 00:09, Avri Altman wrote:
> Maybe we should create some linkage to DOORBELL_CLR_TOUT_US?

Hi Avri,

Do you perhaps want me to change

	io_schedule_timeout(msecs_to_jiffies(20));

into something like the following?

	io_schedule_timeout(msecs_to_jiffies(min(20, remaining_time)));

Documenting that wait_timeout_us may be exceeded by 20 ms seems like the 
easier solution to me :-)

Thanks,

Bart.

RE: [PATCH 1/4] scsi: ufs: Reduce the clock scaling latency

[Avri Altman]

> On 4/28/22 00:09, Avri Altman wrote:
> > Maybe we should create some linkage to DOORBELL_CLR_TOUT_US?
> 
> Hi Avri,
> 
> Do you perhaps want me to change
> 
>         io_schedule_timeout(msecs_to_jiffies(20));
> 
> into something like the following?
> 
>         io_schedule_timeout(msecs_to_jiffies(min(20, remaining_time)));
> 
> Documenting that wait_timeout_us may be exceeded by 20 ms seems like
> the
> easier solution to me :-)
I meant some fraction of DOORBELL_CLR_TOUT_US but that's fine - 
It is going away anyway.

Thanks,
Avri

> 
> Thanks,
> 
> Bart.

[PATCH 2/4] scsi: ufs: Move a clock scaling check

[Bart Van Assche]

Move a check related to clock scaling into ufshcd_devfreq_scale(). This
patch prepares for adding a second ufshcd_clock_scaling_prepare()
caller.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index a3fecbb403d3..3c83f4049031 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1223,8 +1223,7 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
 	ufshcd_scsi_block_requests(hba);
 	down_write(&hba->clk_scaling_lock);
 
-	if (!hba->clk_scaling.is_allowed ||
-	    ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
+	if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
 		ret = -EBUSY;
 		up_write(&hba->clk_scaling_lock);
 		ufshcd_scsi_unblock_requests(hba);
@@ -1262,10 +1261,18 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
 	int ret = 0;
 	bool is_writelock = true;
 
+	if (!hba->clk_scaling.is_allowed)
+		return -EBUSY;
+
 	ret = ufshcd_clock_scaling_prepare(hba);
 	if (ret)
 		return ret;
 
+	if (!hba->clk_scaling.is_allowed) {
+		ret = -EBUSY;
+		goto out_unprepare;
+	}
+
 	/* scale down the gear before scaling down clocks */
 	if (!scale_up) {
 		ret = ufshcd_scale_gear(hba, false);

RE: [PATCH 2/4] scsi: ufs: Move a clock scaling check

[Avri Altman]

> 
> Move a check related to clock scaling into ufshcd_devfreq_scale(). This
> patch prepares for adding a second ufshcd_clock_scaling_prepare()
> caller.
A caller for ufshcd_clock_scaling_prepare() in which clk_scaling is not allowed ?

Thanks,
Avri

> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  drivers/scsi/ufs/ufshcd.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index a3fecbb403d3..3c83f4049031 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1223,8 +1223,7 @@ static int ufshcd_clock_scaling_prepare(struct
> ufs_hba *hba)
>         ufshcd_scsi_block_requests(hba);
>         down_write(&hba->clk_scaling_lock);
> 
> -       if (!hba->clk_scaling.is_allowed ||
> -           ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
> +       if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
>                 ret = -EBUSY;
>                 up_write(&hba->clk_scaling_lock);
>                 ufshcd_scsi_unblock_requests(hba);
> @@ -1262,10 +1261,18 @@ static int ufshcd_devfreq_scale(struct ufs_hba
> *hba, bool scale_up)
>         int ret = 0;
>         bool is_writelock = true;
> 
> +       if (!hba->clk_scaling.is_allowed)
> +               return -EBUSY;
> +
>         ret = ufshcd_clock_scaling_prepare(hba);
>         if (ret)
>                 return ret;
> 
> +       if (!hba->clk_scaling.is_allowed) {
> +               ret = -EBUSY;
> +               goto out_unprepare;
> +       }
> +
>         /* scale down the gear before scaling down clocks */
>         if (!scale_up) {
>                 ret = ufshcd_scale_gear(hba, false);

Re: [PATCH 2/4] scsi: ufs: Move a clock scaling check

[Bart Van Assche]

On 4/28/22 00:38, Avri Altman wrote:
>> Move a check related to clock scaling into ufshcd_devfreq_scale(). This
>> patch prepares for adding a second ufshcd_clock_scaling_prepare()
>> caller.
>
> A caller for ufshcd_clock_scaling_prepare() in which clk_scaling is not allowed ?

Hi Avri,

This patch prepares for adding a caller from outside the clock scaling 
code path. I will integrate this text in the patch description.

Thanks,

Bart.

[PATCH 3/4] scsi: ufs: Pass the clock scaling timeout as an argument

[Bart Van Assche]

Prepare for adding an additional ufshcd_clock_scaling_prepare() call
with a different timeout.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 3c83f4049031..60ba11b68735 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1108,6 +1108,12 @@ static u32 ufshcd_pending_cmds(struct ufs_hba *hba)
 	return pending;
 }
 
+/*
+ * Wait until all pending SCSI commands and TMFs have finished or the timeout
+ * has expired.
+ *
+ * Return: 0 upon success; -EBUSY upon timeout.
+ */
 static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 					u64 wait_timeout_us)
 {
@@ -1212,9 +1218,14 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, bool scale_up)
 	return ret;
 }
 
-static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
+/*
+ * Wait until all pending SCSI commands and TMFs have finished or the timeout
+ * has expired.
+ *
+ * Return: 0 upon success; -EBUSY upon timeout.
+ */
+static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba, u64 timeout_us)
 {
-	#define DOORBELL_CLR_TOUT_US		(1000 * 1000) /* 1 sec */
 	int ret = 0;
 	/*
 	 * make sure that there are no outstanding requests when
@@ -1223,7 +1234,7 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
 	ufshcd_scsi_block_requests(hba);
 	down_write(&hba->clk_scaling_lock);
 
-	if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
+	if (ufshcd_wait_for_doorbell_clr(hba, timeout_us)) {
 		ret = -EBUSY;
 		up_write(&hba->clk_scaling_lock);
 		ufshcd_scsi_unblock_requests(hba);
@@ -1264,7 +1275,7 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
 	if (!hba->clk_scaling.is_allowed)
 		return -EBUSY;
 
-	ret = ufshcd_clock_scaling_prepare(hba);
+	ret = ufshcd_clock_scaling_prepare(hba, 1 * USEC_PER_SEC);
 	if (ret)
 		return ret;
 

RE: [PATCH 3/4] scsi: ufs: Pass the clock scaling timeout as an argument

[Avri Altman]

> Prepare for adding an additional ufshcd_clock_scaling_prepare() call
> with a different timeout.
> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Avri Altman <avri.altman@wdc.com>

> ---
>  drivers/scsi/ufs/ufshcd.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 3c83f4049031..60ba11b68735 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1108,6 +1108,12 @@ static u32 ufshcd_pending_cmds(struct ufs_hba
> *hba)
>         return pending;
>  }
> 
> +/*
> + * Wait until all pending SCSI commands and TMFs have finished or the
> timeout
> + * has expired.
> + *
> + * Return: 0 upon success; -EBUSY upon timeout.
> + */
>  static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
>                                         u64 wait_timeout_us)
>  {
> @@ -1212,9 +1218,14 @@ static int ufshcd_scale_gear(struct ufs_hba *hba,
> bool scale_up)
>         return ret;
>  }
> 
> -static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
> +/*
> + * Wait until all pending SCSI commands and TMFs have finished or the
> timeout
> + * has expired.
> + *
> + * Return: 0 upon success; -EBUSY upon timeout.
> + */
> +static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba, u64
> timeout_us)
>  {
> -       #define DOORBELL_CLR_TOUT_US            (1000 * 1000) /* 1 sec */
>         int ret = 0;
>         /*
>          * make sure that there are no outstanding requests when
> @@ -1223,7 +1234,7 @@ static int ufshcd_clock_scaling_prepare(struct
> ufs_hba *hba)
>         ufshcd_scsi_block_requests(hba);
>         down_write(&hba->clk_scaling_lock);
> 
> -       if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
> +       if (ufshcd_wait_for_doorbell_clr(hba, timeout_us)) {
>                 ret = -EBUSY;
>                 up_write(&hba->clk_scaling_lock);
>                 ufshcd_scsi_unblock_requests(hba);
> @@ -1264,7 +1275,7 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba,
> bool scale_up)
>         if (!hba->clk_scaling.is_allowed)
>                 return -EBUSY;
> 
> -       ret = ufshcd_clock_scaling_prepare(hba);
> +       ret = ufshcd_clock_scaling_prepare(hba, 1 * USEC_PER_SEC);
>         if (ret)
>                 return ret;

[PATCH 4/4] scsi: ufs: Add suspend/resume SCSI command processing support

[Bart Van Assche]

This functionality is needed by UFS drivers to e.g. suspend SCSI command
processing while reprogramming encryption keys if the hardware does not
support concurrent I/O and key reprogramming.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 20 ++++++++++++++++++++
 drivers/scsi/ufs/ufshcd.h |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 60ba11b68735..22447c4f16a2 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1692,6 +1692,26 @@ static void ufshcd_ungate_work(struct work_struct *work)
 	ufshcd_scsi_unblock_requests(hba);
 }
 
+/*
+ * Block processing of new SCSI commands and wait until pending SCSI
+ * commands and TMFs have finished. ufshcd_exec_dev_cmd() and
+ * ufshcd_issue_devman_upiu_cmd() are not affected by this function.
+ *
+ * Return: 0 upon success; -EBUSY upon timeout.
+ */
+int ufshcd_freeze_scsi_devs(struct ufs_hba *hba, u64 timeout_us)
+{
+	return ufshcd_clock_scaling_prepare(hba, timeout_us);
+}
+EXPORT_SYMBOL_GPL(ufshcd_freeze_scsi_devs);
+
+/* Resume processing of SCSI commands. */
+void ufshcd_unfreeze_scsi_devs(struct ufs_hba *hba)
+{
+	ufshcd_clock_scaling_unprepare(hba, true);
+}
+EXPORT_SYMBOL_GPL(ufshcd_unfreeze_scsi_devs);
+
 /**
  * ufshcd_hold - Enable clocks that were gated earlier due to ufshcd_release.
  * Also, exit from hibern8 mode and set the link as active.
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 2b0f3441b813..8954fcbdaf6f 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -1181,6 +1181,9 @@ void ufshcd_release(struct ufs_hba *hba);
 
 void ufshcd_clkgate_delay_set(struct device *dev, unsigned long value);
 
+int ufshcd_freeze_scsi_devs(struct ufs_hba *hba, u64 timeout_us);
+void ufshcd_unfreeze_scsi_devs(struct ufs_hba *hba);
+
 void ufshcd_map_desc_id_to_length(struct ufs_hba *hba, enum desc_idn desc_id,
 				  int *desc_length);