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[PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER

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  [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER Sricharan R <sricharan@codeaurora.org> - 2017-05-18 17:00 +0200
    Re: [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-05-22 12:40 +0200
      Re: [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER Sricharan R <sricharan@codeaurora.org> - 2017-05-22 13:10 +0200
        Re: [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-05-22 13:40 +0200
          Re: [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER Sricharan R <sricharan@codeaurora.org> - 2017-05-22 15:10 +0200

#1644646 — [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER

While deferring the probe of IOMMU masters, xlate and
add_device callbacks called from iort_iommu_configure
can pass back error values like -ENODEV, which means
the IOMMU cannot be connected with that master for real
reasons. Before the IOMMU probe deferral, all such errors
were ignored. Now all those errors are propagated back,
killing the master's probe for such errors. Instead ignore
all the errors except EPROBE_DEFER, which is the only one
of concern and let the master work without IOMMU, thus
restoring the old behavior.

Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
Signed-off-by: Sricharan R <sricharan@codeaurora.org>
---
[V4] Added this patch newly.

 drivers/acpi/arm64/iort.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index c5fecf9..16e101f 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
 	if (err)
 		ops = ERR_PTR(err);
 
+	/* Ignore all other errors apart from EPROBE_DEFER */
+	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
+		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
+		ops = NULL;
+	}
+
 	return ops;
 }
 
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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#1646722

Hi Sricharan,

On Thu, May 18, 2017 at 08:24:16PM +0530, Sricharan R wrote:
> While deferring the probe of IOMMU masters, xlate and
> add_device callbacks called from iort_iommu_configure
> can pass back error values like -ENODEV, which means
> the IOMMU cannot be connected with that master for real
> reasons. Before the IOMMU probe deferral, all such errors
> were ignored. Now all those errors are propagated back,
> killing the master's probe for such errors. Instead ignore
> all the errors except EPROBE_DEFER, which is the only one
> of concern and let the master work without IOMMU, thus
> restoring the old behavior.
> 
> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> ---
> [V4] Added this patch newly.
> 
>  drivers/acpi/arm64/iort.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index c5fecf9..16e101f 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>  	if (err)
>  		ops = ERR_PTR(err);
>  
> +	/* Ignore all other errors apart from EPROBE_DEFER */
> +	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
> +		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
> +		ops = NULL;
> +	}
> +
>  	return ops;
>  }
>  

It is getting a bit convoluted. Is not it better to propagate the
error back and let acpi_dma_configure() make a decision accordingly ?

Something like:

-- >8 --
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index e39ec7b..3a10d757 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1371,8 +1371,8 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
 	iort_set_dma_mask(dev);
 
 	iommu = iort_iommu_configure(dev);
-	if (IS_ERR(iommu))
-		return PTR_ERR(iommu);
+	if (IS_ERR(iommu) && PTR_ERR(iommu) == -EPROBE_DEFER)
+		return -EPROBE_DEFER;
 
 	size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
 	/*

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#1646744

Hi Lorenzo,

On 5/22/2017 4:07 PM, Lorenzo Pieralisi wrote:
> Hi Sricharan,
> 
> On Thu, May 18, 2017 at 08:24:16PM +0530, Sricharan R wrote:
>> While deferring the probe of IOMMU masters, xlate and
>> add_device callbacks called from iort_iommu_configure
>> can pass back error values like -ENODEV, which means
>> the IOMMU cannot be connected with that master for real
>> reasons. Before the IOMMU probe deferral, all such errors
>> were ignored. Now all those errors are propagated back,
>> killing the master's probe for such errors. Instead ignore
>> all the errors except EPROBE_DEFER, which is the only one
>> of concern and let the master work without IOMMU, thus
>> restoring the old behavior.
>>
>> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
>> ---
>> [V4] Added this patch newly.
>>
>>  drivers/acpi/arm64/iort.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>> index c5fecf9..16e101f 100644
>> --- a/drivers/acpi/arm64/iort.c
>> +++ b/drivers/acpi/arm64/iort.c
>> @@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>>  	if (err)
>>  		ops = ERR_PTR(err);
>>  
>> +	/* Ignore all other errors apart from EPROBE_DEFER */
>> +	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
>> +		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
>> +		ops = NULL;
>> +	}
>> +
>>  	return ops;
>>  }
>>  
> 
> It is getting a bit convoluted. Is not it better to propagate the
> error back and let acpi_dma_configure() make a decision accordingly ?
> 

ok, I was trying to keep it in same way as DT, where of_dma_configure
(here acpi_dma_configure) calls of_iommu_configure(here iort_iommu_configure)
which ends up doing the check. So will have to be changed in both places
for symmetry.

> Something like:
> 
> -- >8 --
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index e39ec7b..3a10d757 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1371,8 +1371,8 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
>  	iort_set_dma_mask(dev);
>  
>  	iommu = iort_iommu_configure(dev);
> -	if (IS_ERR(iommu))
> -		return PTR_ERR(iommu);
> +	if (IS_ERR(iommu) && PTR_ERR(iommu) == -EPROBE_DEFER)
> +		return -EPROBE_DEFER;

In case of other errors apart from EPROBE_DEFER,
iommu = NULL should be set, before passing it on to
arch_setup_dma_ops.

Regards,
 Sricharan

>  
>  	size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
>  	/*
> 

-- 
"QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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#1646773

On Mon, May 22, 2017 at 04:35:43PM +0530, Sricharan R wrote:
> Hi Lorenzo,
> 
> On 5/22/2017 4:07 PM, Lorenzo Pieralisi wrote:
> > Hi Sricharan,
> > 
> > On Thu, May 18, 2017 at 08:24:16PM +0530, Sricharan R wrote:
> >> While deferring the probe of IOMMU masters, xlate and
> >> add_device callbacks called from iort_iommu_configure
> >> can pass back error values like -ENODEV, which means
> >> the IOMMU cannot be connected with that master for real
> >> reasons. Before the IOMMU probe deferral, all such errors
> >> were ignored. Now all those errors are propagated back,
> >> killing the master's probe for such errors. Instead ignore
> >> all the errors except EPROBE_DEFER, which is the only one
> >> of concern and let the master work without IOMMU, thus
> >> restoring the old behavior.
> >>
> >> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
> >> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> >> ---
> >> [V4] Added this patch newly.
> >>
> >>  drivers/acpi/arm64/iort.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>
> >> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> >> index c5fecf9..16e101f 100644
> >> --- a/drivers/acpi/arm64/iort.c
> >> +++ b/drivers/acpi/arm64/iort.c
> >> @@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
> >>  	if (err)
> >>  		ops = ERR_PTR(err);
> >>  
> >> +	/* Ignore all other errors apart from EPROBE_DEFER */
> >> +	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
> >> +		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
> >> +		ops = NULL;
> >> +	}
> >> +
> >>  	return ops;
> >>  }
> >>  
> > 
> > It is getting a bit convoluted. Is not it better to propagate the
> > error back and let acpi_dma_configure() make a decision accordingly ?
> > 
> 
> ok, I was trying to keep it in same way as DT, where of_dma_configure
> (here acpi_dma_configure) calls of_iommu_configure(here iort_iommu_configure)
> which ends up doing the check. So will have to be changed in both places
> for symmetry.
> 
> > Something like:
> > 
> > -- >8 --
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index e39ec7b..3a10d757 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -1371,8 +1371,8 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
> >  	iort_set_dma_mask(dev);
> >  
> >  	iommu = iort_iommu_configure(dev);
> > -	if (IS_ERR(iommu))
> > -		return PTR_ERR(iommu);
> > +	if (IS_ERR(iommu) && PTR_ERR(iommu) == -EPROBE_DEFER)
> > +		return -EPROBE_DEFER;
> 
> In case of other errors apart from EPROBE_DEFER,
> iommu = NULL should be set, before passing it on to
> arch_setup_dma_ops.

Ah yes, sorry, that makes it uglier :(

Point is, it does not make sense to me to have of/acpi_dma_configure()
check a return code with (IS_ERR()) whilst we know the only error
code you are allowed to handle is -EPROBE_DEFER, while at it it is
better to make the -EPROBE_DEFER check explicit (otherwise it may
seem that of/acpi_dma_configure() can handle an error code that
is different from -EPROBE_DEFER - but they don't), no big deal either
way though.

Lorenzo

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#1646860

Hi Lorenzo,

On 5/22/2017 5:01 PM, Lorenzo Pieralisi wrote:
> On Mon, May 22, 2017 at 04:35:43PM +0530, Sricharan R wrote:
>> Hi Lorenzo,
>>
>> On 5/22/2017 4:07 PM, Lorenzo Pieralisi wrote:
>>> Hi Sricharan,
>>>
>>> On Thu, May 18, 2017 at 08:24:16PM +0530, Sricharan R wrote:
>>>> While deferring the probe of IOMMU masters, xlate and
>>>> add_device callbacks called from iort_iommu_configure
>>>> can pass back error values like -ENODEV, which means
>>>> the IOMMU cannot be connected with that master for real
>>>> reasons. Before the IOMMU probe deferral, all such errors
>>>> were ignored. Now all those errors are propagated back,
>>>> killing the master's probe for such errors. Instead ignore
>>>> all the errors except EPROBE_DEFER, which is the only one
>>>> of concern and let the master work without IOMMU, thus
>>>> restoring the old behavior.
>>>>
>>>> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
>>>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
>>>> ---
>>>> [V4] Added this patch newly.
>>>>
>>>>  drivers/acpi/arm64/iort.c | 6 ++++++
>>>>  1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>>>> index c5fecf9..16e101f 100644
>>>> --- a/drivers/acpi/arm64/iort.c
>>>> +++ b/drivers/acpi/arm64/iort.c
>>>> @@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>>>>  	if (err)
>>>>  		ops = ERR_PTR(err);
>>>>  
>>>> +	/* Ignore all other errors apart from EPROBE_DEFER */
>>>> +	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
>>>> +		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
>>>> +		ops = NULL;
>>>> +	}
>>>> +
>>>>  	return ops;
>>>>  }
>>>>  
>>>
>>> It is getting a bit convoluted. Is not it better to propagate the
>>> error back and let acpi_dma_configure() make a decision accordingly ?
>>>
>>
>> ok, I was trying to keep it in same way as DT, where of_dma_configure
>> (here acpi_dma_configure) calls of_iommu_configure(here iort_iommu_configure)
>> which ends up doing the check. So will have to be changed in both places
>> for symmetry.
>>
>>> Something like:
>>>
>>> -- >8 --
>>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>>> index e39ec7b..3a10d757 100644
>>> --- a/drivers/acpi/scan.c
>>> +++ b/drivers/acpi/scan.c
>>> @@ -1371,8 +1371,8 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
>>>  	iort_set_dma_mask(dev);
>>>  
>>>  	iommu = iort_iommu_configure(dev);
>>> -	if (IS_ERR(iommu))
>>> -		return PTR_ERR(iommu);
>>> +	if (IS_ERR(iommu) && PTR_ERR(iommu) == -EPROBE_DEFER)
>>> +		return -EPROBE_DEFER;
>>
>> In case of other errors apart from EPROBE_DEFER,
>> iommu = NULL should be set, before passing it on to
>> arch_setup_dma_ops.
> 
> Ah yes, sorry, that makes it uglier :(
> 
> Point is, it does not make sense to me to have of/acpi_dma_configure()
> check a return code with (IS_ERR()) whilst we know the only error
> code you are allowed to handle is -EPROBE_DEFER, while at it it is
> better to make the -EPROBE_DEFER check explicit (otherwise it may
> seem that of/acpi_dma_configure() can handle an error code that
> is different from -EPROBE_DEFER - but they don't), no big deal either
> way though.
> 

ok, in which case, the above check that you have shown
to be added additionally to the original patch.

Regards,
 Sricharan

-- 
"QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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