[PATCH v2] scsi: ufshcd: fix possible unclocked register access

[PATCH v2] scsi: ufshcd: fix possible unclocked register access

[Subhash Jadavani]

Vendor specific setup_clocks callback may require the clocks managed
by ufshcd driver to be ON. So if the vendor specific setup_clocks callback
is called while the required clocks are turned off, it could result into
unclocked register access.

To prevent possible unclock register access, this change makes sure that
required clocks remain enabled before calling into vendor specific
setup_clocks callback.

Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
---
Changes from v2:
* Don't call ufshcd_vops_setup_clocks() again for clock off
---
 drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 05c7456..c1a77d3 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba *hba, bool on,
 	if (!head || list_empty(head))
 		goto out;
 
+	/*
+	 * vendor specific setup_clocks ops may depend on clocks managed by
+	 * this standard driver hence call the vendor specific setup_clocks
+	 * before disabling the clocks managed here.
+	 */
+	if (!on) {
+		ret = ufshcd_vops_setup_clocks(hba, on);
+		if (ret)
+			return ret;
+	}
+
 	list_for_each_entry(clki, head, list) {
 		if (!IS_ERR_OR_NULL(clki->clk)) {
 			if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
@@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba *hba, bool on,
 		}
 	}
 
-	ret = ufshcd_vops_setup_clocks(hba, on);
+	/*
+	 * vendor specific setup_clocks ops may depend on clocks managed by
+	 * this standard driver hence call the vendor specific setup_clocks
+	 * after enabling the clocks managed here.
+	 */
+	if (on) {
+		ret = ufshcd_vops_setup_clocks(hba, on);
+		if (ret)
+			return ret;
+	}
 out:
 	if (ret) {
 		list_for_each_entry(clki, head, list) {
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

RE: [PATCH v2] scsi: ufshcd: fix possible unclocked register access

[Kiwoong Kim]

Hi, Subhash.

Some UFS host controllers may need to call the vendor specific callback
before and after controlling by clock control framework,
regardless of whether available clocks are turned on or off.

Is there any special reason to limit to invoke the callback
only when the clocks are turned on or not?
Besides, the callback is acknowledged from core driver
because 2nd argument is whether the clocks are turned on or not.

If you have any other idea, please let me know.

Thanks
Regards

> Vendor specific setup_clocks callback may require the clocks managed
> by ufshcd driver to be ON. So if the vendor specific setup_clocks callback
> is called while the required clocks are turned off, it could result into
> unclocked register access.
> 
> To prevent possible unclock register access, this change makes sure that
> required clocks remain enabled before calling into vendor specific
> setup_clocks callback.
> 
> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
> ---
> Changes from v2:
> * Don't call ufshcd_vops_setup_clocks() again for clock off
> ---
>  drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 05c7456..c1a77d3 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> *hba, bool on,
>  	if (!head || list_empty(head))
>  		goto out;
> 
> +	/*
> +	 * vendor specific setup_clocks ops may depend on clocks managed by
> +	 * this standard driver hence call the vendor specific setup_clocks
> +	 * before disabling the clocks managed here.
> +	 */
> +	if (!on) {
> +		ret = ufshcd_vops_setup_clocks(hba, on);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	list_for_each_entry(clki, head, list) {
>  		if (!IS_ERR_OR_NULL(clki->clk)) {
>  			if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
> @@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> *hba, bool on,
>  		}
>  	}
> 
> -	ret = ufshcd_vops_setup_clocks(hba, on);
> +	/*
> +	 * vendor specific setup_clocks ops may depend on clocks managed by
> +	 * this standard driver hence call the vendor specific setup_clocks
> +	 * after enabling the clocks managed here.
> +	 */
> +	if (on) {
> +		ret = ufshcd_vops_setup_clocks(hba, on);
> +		if (ret)
> +			return ret;
> +	}
>  out:
>  	if (ret) {
>  		list_for_each_entry(clki, head, list) {
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
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Re: [PATCH v2] scsi: ufshcd: fix possible unclocked register access

[Subhash Jadavani]

Thanks Kim for the response.

On 2016-10-06 03:28, Kiwoong Kim wrote:
> Hi, Subhash.
> 
> Some UFS host controllers may need to call the vendor specific callback
> before and after controlling by clock control framework,
> regardless of whether available clocks are turned on or off.

Are you suggesting to call ufshcd_vops_setup_clocks() 2 times, one 
before the on/off by ufshcd core driver and one after the on/off? If 
yes, then we also have add 3rd argument clarifying if this is PRE_CHANGE 
or POST_CHANGE.

> 
> Is there any special reason to limit to invoke the callback
> only when the clocks are turned on or not?
> 
> Besides, the callback is acknowledged from core driver
> because 2nd argument is whether the clocks are turned on or not.
> 
> If you have any other idea, please let me know.

This is my suggestion:
1. Add 3rd argument to setup_clocks ops to let the vendor callback 
function know if this is called PRE_CHANGE or POST_CHANGE.
2. If #1 is in place, call setup_clocks 2 times, one with PRE_CHANGE 
argument before making any clock changes in core driver, 2nd with 
POST_CHANGE argument after making the clock changes to core driver.

Let me know if this would work or not.

Thanks,
Subhash

> 
> Thanks
> Regards
> 
>> Vendor specific setup_clocks callback may require the clocks managed
>> by ufshcd driver to be ON. So if the vendor specific setup_clocks 
>> callback
>> is called while the required clocks are turned off, it could result 
>> into
>> unclocked register access.
>> 
>> To prevent possible unclock register access, this change makes sure 
>> that
>> required clocks remain enabled before calling into vendor specific
>> setup_clocks callback.
>> 
>> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> ---
>> Changes from v2:
>> * Don't call ufshcd_vops_setup_clocks() again for clock off
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++-
>>  1 file changed, 21 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 05c7456..c1a77d3 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba
>> *hba, bool on,
>>  	if (!head || list_empty(head))
>>  		goto out;
>> 
>> +	/*
>> +	 * vendor specific setup_clocks ops may depend on clocks managed by
>> +	 * this standard driver hence call the vendor specific setup_clocks
>> +	 * before disabling the clocks managed here.
>> +	 */
>> +	if (!on) {
>> +		ret = ufshcd_vops_setup_clocks(hba, on);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>>  	list_for_each_entry(clki, head, list) {
>>  		if (!IS_ERR_OR_NULL(clki->clk)) {
>>  			if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
>> @@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba
>> *hba, bool on,
>>  		}
>>  	}
>> 
>> -	ret = ufshcd_vops_setup_clocks(hba, on);
>> +	/*
>> +	 * vendor specific setup_clocks ops may depend on clocks managed by
>> +	 * this standard driver hence call the vendor specific setup_clocks
>> +	 * after enabling the clocks managed here.
>> +	 */
>> +	if (on) {
>> +		ret = ufshcd_vops_setup_clocks(hba, on);
>> +		if (ret)
>> +			return ret;
>> +	}
>>  out:
>>  	if (ret) {
>>  		list_for_each_entry(clki, head, list) {
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-scsi" 
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
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> in
> the body of a message to majordomo@vger.kernel.org
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-- 
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a Linux Foundation Collaborative Project

RE: [PATCH v2] scsi: ufshcd: fix possible unclocked register access

[Kiwoong Kim]

Hi, Subhash.

> Thanks Kim for the response.
> 
> On 2016-10-06 03:28, Kiwoong Kim wrote:
> > Hi, Subhash.
> >
> > Some UFS host controllers may need to call the vendor specific
> > callback before and after controlling by clock control framework,
> > regardless of whether available clocks are turned on or off.
> 
> Are you suggesting to call ufshcd_vops_setup_clocks() 2 times, one before
> the on/off by ufshcd core driver and one after the on/off? If yes, then we
> also have add 3rd argument clarifying if this is PRE_CHANGE or
POST_CHANGE.
> 
> >
> > Is there any special reason to limit to invoke the callback
> > only when the clocks are turned on or not?
> >
> > Besides, the callback is acknowledged from core driver
> > because 2nd argument is whether the clocks are turned on or not.
> >
> > If you have any other idea, please let me know.
> 
> This is my suggestion:
> 1. Add 3rd argument to setup_clocks ops to let the vendor callback
> function know if this is called PRE_CHANGE or POST_CHANGE.
> 2. If #1 is in place, call setup_clocks 2 times, one with PRE_CHANGE
> argument before making any clock changes in core driver, 2nd with
> POST_CHANGE argument after making the clock changes to core driver.

Yes, that's exactly the same what I mean.

Thanks


> 
> Let me know if this would work or not.
> 
> Thanks,
> Subhash
> 
> >
> > Thanks
> > Regards
> >
> >> Vendor specific setup_clocks callback may require the clocks managed
> >> by ufshcd driver to be ON. So if the vendor specific setup_clocks
> >> callback
> >> is called while the required clocks are turned off, it could result
> >> into
> >> unclocked register access.
> >>
> >> To prevent possible unclock register access, this change makes sure
> >> that
> >> required clocks remain enabled before calling into vendor specific
> >> setup_clocks callback.
> >>
> >> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
> >> ---
> >> Changes from v2:
> >> * Don't call ufshcd_vops_setup_clocks() again for clock off
> >> ---
> >>  drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++-
> >>  1 file changed, 21 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> >> index 05c7456..c1a77d3 100644
> >> --- a/drivers/scsi/ufs/ufshcd.c
> >> +++ b/drivers/scsi/ufs/ufshcd.c
> >> @@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> >> *hba, bool on,
> >>  	if (!head || list_empty(head))
> >>  		goto out;
> >>
> >> +	/*
> >> +	 * vendor specific setup_clocks ops may depend on clocks managed by
> >> +	 * this standard driver hence call the vendor specific setup_clocks
> >> +	 * before disabling the clocks managed here.
> >> +	 */
> >> +	if (!on) {
> >> +		ret = ufshcd_vops_setup_clocks(hba, on);
> >> +		if (ret)
> >> +			return ret;
> >> +	}
> >> +
> >>  	list_for_each_entry(clki, head, list) {
> >>  		if (!IS_ERR_OR_NULL(clki->clk)) {
> >>  			if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
> >> @@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> >> *hba, bool on,
> >>  		}
> >>  	}
> >>
> >> -	ret = ufshcd_vops_setup_clocks(hba, on);
> >> +	/*
> >> +	 * vendor specific setup_clocks ops may depend on clocks managed by
> >> +	 * this standard driver hence call the vendor specific setup_clocks
> >> +	 * after enabling the clocks managed here.
> >> +	 */
> >> +	if (on) {
> >> +		ret = ufshcd_vops_setup_clocks(hba, on);
> >> +		if (ret)
> >> +			return ret;
> >> +	}
> >>  out:
> >>  	if (ret) {
> >>  		list_for_each_entry(clki, head, list) {
> >> --
> >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> >> Forum,
> >> a Linux Foundation Collaborative Project
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-scsi"
> >> in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-scsi"
> > in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> --
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
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Re: [PATCH v2] scsi: ufshcd: fix possible unclocked register access

[Subhash Jadavani]

On 2016-10-06 18:16, Kiwoong Kim wrote:
> Hi, Subhash.
> 
>> Thanks Kim for the response.
>> 
>> On 2016-10-06 03:28, Kiwoong Kim wrote:
>> > Hi, Subhash.
>> >
>> > Some UFS host controllers may need to call the vendor specific
>> > callback before and after controlling by clock control framework,
>> > regardless of whether available clocks are turned on or off.
>> 
>> Are you suggesting to call ufshcd_vops_setup_clocks() 2 times, one 
>> before
>> the on/off by ufshcd core driver and one after the on/off? If yes, 
>> then we
>> also have add 3rd argument clarifying if this is PRE_CHANGE or
> POST_CHANGE.
>> 
>> >
>> > Is there any special reason to limit to invoke the callback
>> > only when the clocks are turned on or not?
>> >
>> > Besides, the callback is acknowledged from core driver
>> > because 2nd argument is whether the clocks are turned on or not.
>> >
>> > If you have any other idea, please let me know.
>> 
>> This is my suggestion:
>> 1. Add 3rd argument to setup_clocks ops to let the vendor callback
>> function know if this is called PRE_CHANGE or POST_CHANGE.
>> 2. If #1 is in place, call setup_clocks 2 times, one with PRE_CHANGE
>> argument before making any clock changes in core driver, 2nd with
>> POST_CHANGE argument after making the clock changes to core driver.
> 
> Yes, that's exactly the same what I mean.

Thanks, Will send out new version adding that.

> 
> Thanks
> 
> 
>> 
>> Let me know if this would work or not.
>> 
>> Thanks,
>> Subhash
>> 
>> >
>> > Thanks
>> > Regards
>> >
>> >> Vendor specific setup_clocks callback may require the clocks managed
>> >> by ufshcd driver to be ON. So if the vendor specific setup_clocks
>> >> callback
>> >> is called while the required clocks are turned off, it could result
>> >> into
>> >> unclocked register access.
>> >>
>> >> To prevent possible unclock register access, this change makes sure
>> >> that
>> >> required clocks remain enabled before calling into vendor specific
>> >> setup_clocks callback.
>> >>
>> >> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> >> ---
>> >> Changes from v2:
>> >> * Don't call ufshcd_vops_setup_clocks() again for clock off
>> >> ---
>> >>  drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++-
>> >>  1 file changed, 21 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> >> index 05c7456..c1a77d3 100644
>> >> --- a/drivers/scsi/ufs/ufshcd.c
>> >> +++ b/drivers/scsi/ufs/ufshcd.c
>> >> @@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba
>> >> *hba, bool on,
>> >>  	if (!head || list_empty(head))
>> >>  		goto out;
>> >>
>> >> +	/*
>> >> +	 * vendor specific setup_clocks ops may depend on clocks managed by
>> >> +	 * this standard driver hence call the vendor specific setup_clocks
>> >> +	 * before disabling the clocks managed here.
>> >> +	 */
>> >> +	if (!on) {
>> >> +		ret = ufshcd_vops_setup_clocks(hba, on);
>> >> +		if (ret)
>> >> +			return ret;
>> >> +	}
>> >> +
>> >>  	list_for_each_entry(clki, head, list) {
>> >>  		if (!IS_ERR_OR_NULL(clki->clk)) {
>> >>  			if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
>> >> @@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba
>> >> *hba, bool on,
>> >>  		}
>> >>  	}
>> >>
>> >> -	ret = ufshcd_vops_setup_clocks(hba, on);
>> >> +	/*
>> >> +	 * vendor specific setup_clocks ops may depend on clocks managed by
>> >> +	 * this standard driver hence call the vendor specific setup_clocks
>> >> +	 * after enabling the clocks managed here.
>> >> +	 */
>> >> +	if (on) {
>> >> +		ret = ufshcd_vops_setup_clocks(hba, on);
>> >> +		if (ret)
>> >> +			return ret;
>> >> +	}
>> >>  out:
>> >>  	if (ret) {
>> >>  		list_for_each_entry(clki, head, list) {
>> >> --
>> >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> >> Forum,
>> >> a Linux Foundation Collaborative Project
>> >>
>> >> --
>> >> To unsubscribe from this list: send the line "unsubscribe linux-scsi"
>> >> in
>> >> the body of a message to majordomo@vger.kernel.org
>> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> >
>> >
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe linux-scsi"
>> > in
>> > the body of a message to majordomo@vger.kernel.org
>> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
>> --
>> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-scsi" 
>> in
>> the body of a message to majordomo@vger.kernel.org
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> 
> 
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-- 
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