[RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Santosh Shilimkar]

DMA bounce limit is the maximum direct DMA'able memory beyond which
bounce buffers has to be used to perform dma operations. SCSI driver
relies on dma_mask but its calculation is based on max_*pfn which
don't have uniform meaning across architectures. So make use of
dma_max_pfn() which is expected to return the DMAable maximum pfn
value across architectures.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-scsi@vger.kernel.org

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
---
 drivers/scsi/scsi_lib.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 86d5220..e8275fa 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
 
 	host_dev = scsi_get_device(shost);
 	if (host_dev && host_dev->dma_mask)
-		bounce_limit = *host_dev->dma_mask;
+		bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;
 
 	return bounce_limit;
 }
-- 
1.7.9.5

Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Sergei Shtylyov]

Hello.

On 07/13/2013 01:48 AM, Santosh Shilimkar wrote:

> DMA bounce limit is the maximum direct DMA'able memory beyond which
> bounce buffers has to be used to perform dma operations. SCSI driver
> relies on dma_mask but its calculation is based on max_*pfn which
> don't have uniform meaning across architectures. So make use of
> dma_max_pfn() which is expected to return the DMAable maximum pfn
> value across architectures.

> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: linux-scsi@vger.kernel.org

> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> ---
>   drivers/scsi/scsi_lib.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 86d5220..e8275fa 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
>
>   	host_dev = scsi_get_device(shost);
>   	if (host_dev && host_dev->dma_mask)
> -		bounce_limit = *host_dev->dma_mask;
> +		bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;

    You definitely forgot -1 here.

WBR, Sergei

Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Russell King - ARM Linux]

On Sat, Jul 13, 2013 at 01:55:58AM +0400, Sergei Shtylyov wrote:
> Hello.
>
> On 07/13/2013 01:48 AM, Santosh Shilimkar wrote:
>
>> DMA bounce limit is the maximum direct DMA'able memory beyond which
>> bounce buffers has to be used to perform dma operations. SCSI driver
>> relies on dma_mask but its calculation is based on max_*pfn which
>> don't have uniform meaning across architectures. So make use of
>> dma_max_pfn() which is expected to return the DMAable maximum pfn
>> value across architectures.
>
>> Cc: Russell King <linux@arm.linux.org.uk>
>> Cc: linux-scsi@vger.kernel.org
>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>> ---
>>   drivers/scsi/scsi_lib.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>
>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>> index 86d5220..e8275fa 100644
>> --- a/drivers/scsi/scsi_lib.c
>> +++ b/drivers/scsi/scsi_lib.c
>> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
>>
>>   	host_dev = scsi_get_device(shost);
>>   	if (host_dev && host_dev->dma_mask)
>> -		bounce_limit = *host_dev->dma_mask;
>> +		bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;
>
>    You definitely forgot -1 here.

Please explain your point.

Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Sergei Shtylyov]

Hello.

On 07/13/2013 02:25 AM, Russell King - ARM Linux wrote:

>>> DMA bounce limit is the maximum direct DMA'able memory beyond which
>>> bounce buffers has to be used to perform dma operations. SCSI driver
>>> relies on dma_mask but its calculation is based on max_*pfn which
>>> don't have uniform meaning across architectures. So make use of
>>> dma_max_pfn() which is expected to return the DMAable maximum pfn
>>> value across architectures.

>>> Cc: Russell King <linux@arm.linux.org.uk>
>>> Cc: linux-scsi@vger.kernel.org

>>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>>> ---
>>>    drivers/scsi/scsi_lib.c |    2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)

>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>>> index 86d5220..e8275fa 100644
>>> --- a/drivers/scsi/scsi_lib.c
>>> +++ b/drivers/scsi/scsi_lib.c
>>> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
>>>
>>>    	host_dev = scsi_get_device(shost);
>>>    	if (host_dev && host_dev->dma_mask)
>>> -		bounce_limit = *host_dev->dma_mask;
>>> +		bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;

>>     You definitely forgot -1 here.

> Please explain your point.

    Previously, 'bounce_limit' would look like 0xffffffff (unless I'm 
mistaken), now it would look like 0xfffff000 which is hardly what we're 
looking for, no?

WBR, Sergei

Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Sergei Shtylyov]

On 07/13/2013 03:08 AM, Sergei Shtylyov wrote:

>>>> DMA bounce limit is the maximum direct DMA'able memory beyond which
>>>> bounce buffers has to be used to perform dma operations. SCSI driver
>>>> relies on dma_mask but its calculation is based on max_*pfn which
>>>> don't have uniform meaning across architectures. So make use of
>>>> dma_max_pfn() which is expected to return the DMAable maximum pfn
>>>> value across architectures.

>>>> Cc: Russell King <linux@arm.linux.org.uk>
>>>> Cc: linux-scsi@vger.kernel.org

>>>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>>>> ---
>>>>    drivers/scsi/scsi_lib.c |    2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)

>>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>>>> index 86d5220..e8275fa 100644
>>>> --- a/drivers/scsi/scsi_lib.c
>>>> +++ b/drivers/scsi/scsi_lib.c
>>>> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct
>>>> Scsi_Host *shost)
>>>>
>>>>        host_dev = scsi_get_device(shost);
>>>>        if (host_dev && host_dev->dma_mask)
>>>> -        bounce_limit = *host_dev->dma_mask;
>>>> +        bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;

>>>     You definitely forgot -1 here.

>> Please explain your point.

>     Previously, 'bounce_limit' would look like 0xffffffff (unless I'm
> mistaken), now it would look like 0xfffff000 which is hardly what we're
> looking for, no?

    Although, -1 won't give us the correct result in this case, it's 
more like + PAGE_SIZE - 1.

WBR, Sergei

Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations

[Russell King - ARM Linux]

On Sat, Jul 13, 2013 at 03:42:55AM +0400, Sergei Shtylyov wrote:
>>>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>>>>> index 86d5220..e8275fa 100644
>>>>> --- a/drivers/scsi/scsi_lib.c
>>>>> +++ b/drivers/scsi/scsi_lib.c
>>>>> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct
>>>>> Scsi_Host *shost)
>>>>>
>>>>>        host_dev = scsi_get_device(shost);
>>>>>        if (host_dev && host_dev->dma_mask)
>>>>> -        bounce_limit = *host_dev->dma_mask;
>>>>> +        bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;
>
>>>>     You definitely forgot -1 here.
>
>>> Please explain your point.
>
>>     Previously, 'bounce_limit' would look like 0xffffffff (unless I'm
>> mistaken), now it would look like 0xfffff000 which is hardly what we're
>> looking for, no?
>
>    Although, -1 won't give us the correct result in this case, it's more 
> like + PAGE_SIZE - 1.

And where it's used is blk_bounce_limit(), the first which that does
is convert it back to a PFN, losing the bottom bits again...

I'm tempted to suggest converting the whole thing to just deal with
PFNs rather than bytes since we only deal with "can we DMA to this"
on a per-page basis.

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Russell King - ARM Linux]

On Fri, Jul 12, 2013 at 05:48:09PM -0400, Santosh Shilimkar wrote:
> The series is an attempt to move ARM port to NO_BOOTMEM. As discussed
> on list NO_BOOTMEM move needed updates to max*pfn meaning to be maximum
> PFNs but that breaks the dma_mask for few block layer drivers since
> ARM start of physical memory is not PFN0 unlike most of the architectures.
> Some more read on it is here:
> 	http://lwn.net/Articles/543408/
> 	http://lwn.net/Articles/543424/
> 
> To address this issue, we introduce generic dma_max_pfn() helper which
> can be overridden from the architectures.
> 	
> Another intention behind move to nobootmem is also to convert ARM to
> switch to memblock and getting rid of bootmem allocator dependency which
> don't work for LPAE machines which has physical memory starting beyond
> 4 GB boundary. It needs changes to core kernel and also a new memblock
> API. More on this can be found here:
> 	https://lkml.org/lkml/2013/6/29/77
> 
> I have been trying to cook up these patches with kind help from Russell
> and we know series don't solve all the dma_mask bad assumptions. But at
> least I am hoping that it can get the ball rolling.	
> 
> Comments/testing help is welcome !!

As this is related to some of the cleanup of dma_mask which I've been
doing, I think it may make sense to roll this into one tree.  Any
objection to that?

Can we get any acks on this stuff from Jens and Jejb etc - especially
for the bits which touch block/ and for the scsi bits as these are
touching other subsystems.  (oddly, linux-scsi wasn't on the original
mail for this series summary.)

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Santosh Shilimkar]

On Friday 26 July 2013 11:10 AM, Russell King - ARM Linux wrote:
> On Fri, Jul 12, 2013 at 05:48:09PM -0400, Santosh Shilimkar wrote:
>> The series is an attempt to move ARM port to NO_BOOTMEM. As discussed
>> on list NO_BOOTMEM move needed updates to max*pfn meaning to be maximum
>> PFNs but that breaks the dma_mask for few block layer drivers since
>> ARM start of physical memory is not PFN0 unlike most of the architectures.
>> Some more read on it is here:
>> 	http://lwn.net/Articles/543408/
>> 	http://lwn.net/Articles/543424/
>>
>> To address this issue, we introduce generic dma_max_pfn() helper which
>> can be overridden from the architectures.
>> 	
>> Another intention behind move to nobootmem is also to convert ARM to
>> switch to memblock and getting rid of bootmem allocator dependency which
>> don't work for LPAE machines which has physical memory starting beyond
>> 4 GB boundary. It needs changes to core kernel and also a new memblock
>> API. More on this can be found here:
>> 	https://lkml.org/lkml/2013/6/29/77
>>
>> I have been trying to cook up these patches with kind help from Russell
>> and we know series don't solve all the dma_mask bad assumptions. But at
>> least I am hoping that it can get the ball rolling.	
>>
>> Comments/testing help is welcome !!
> 
> As this is related to some of the cleanup of dma_mask which I've been
> doing, I think it may make sense to roll this into one tree.  Any
> objection to that?
> 
> Can we get any acks on this stuff from Jens and Jejb etc - especially
> for the bits which touch block/ and for the scsi bits as these are
> touching other subsystems.  (oddly, linux-scsi wasn't on the original
> mail for this series summary.)
> 
Sorry I missed the scsi lists on the summary patch.

While browsing the code I found another spot in mmc layer which
needs fixing. The patch is at the end of the email with Chris
and linux-mmc cc'ed here.

Regards,
Santosh

>From 06a27a784a1fd86bf22adf1b247ac82a7c21d46b Mon Sep 17 00:00:00 2001
From: Santosh Shilimkar <santosh.shilimkar@ti.com>
Date: Fri, 19 Jul 2013 21:36:46 -0400
Subject: [PATCH] mmc: Use dma_max_pfn(dev) helper for bounce_limit
 calculations

DMA bounce limit is the maximum direct DMA'able memory beyond which
bounce buffers has to be used to perform dma operations. MMC queue layer
relies on dma_mask but its calculation is based on max_*pfn which
don't have uniform meaning across architectures. So make use of
dma_max_pfn() which is expected to return the DMAable maximum pfn
value across architectures.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Chris Ball <cjb@laptop.org>

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
---
 drivers/mmc/card/queue.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index fa9632e..357bbc5 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -15,6 +15,7 @@
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/scatterlist.h>
+#include <linux/dma-mapping.h>
 
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
@@ -196,7 +197,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
 	struct mmc_queue_req *mqrq_prev = &mq->mqrq[1];
 
 	if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
-		limit = *mmc_dev(host)->dma_mask;
+		limit = dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
 
 	mq->card = card;
 	mq->queue = blk_init_queue(mmc_request_fn, lock);
-- 
1.7.9.5

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Russell King - ARM Linux]

On Fri, Jul 26, 2013 at 12:28:26PM -0400, Santosh Shilimkar wrote:
> On Friday 26 July 2013 11:10 AM, Russell King - ARM Linux wrote:
> > On Fri, Jul 12, 2013 at 05:48:09PM -0400, Santosh Shilimkar wrote:
> >> The series is an attempt to move ARM port to NO_BOOTMEM. As discussed
> >> on list NO_BOOTMEM move needed updates to max*pfn meaning to be maximum
> >> PFNs but that breaks the dma_mask for few block layer drivers since
> >> ARM start of physical memory is not PFN0 unlike most of the architectures.
> >> Some more read on it is here:
> >> 	http://lwn.net/Articles/543408/
> >> 	http://lwn.net/Articles/543424/
> >>
> >> To address this issue, we introduce generic dma_max_pfn() helper which
> >> can be overridden from the architectures.
> >> 	
> >> Another intention behind move to nobootmem is also to convert ARM to
> >> switch to memblock and getting rid of bootmem allocator dependency which
> >> don't work for LPAE machines which has physical memory starting beyond
> >> 4 GB boundary. It needs changes to core kernel and also a new memblock
> >> API. More on this can be found here:
> >> 	https://lkml.org/lkml/2013/6/29/77
> >>
> >> I have been trying to cook up these patches with kind help from Russell
> >> and we know series don't solve all the dma_mask bad assumptions. But at
> >> least I am hoping that it can get the ball rolling.	
> >>
> >> Comments/testing help is welcome !!
> > 
> > As this is related to some of the cleanup of dma_mask which I've been
> > doing, I think it may make sense to roll this into one tree.  Any
> > objection to that?
> > 
> > Can we get any acks on this stuff from Jens and Jejb etc - especially
> > for the bits which touch block/ and for the scsi bits as these are
> > touching other subsystems.  (oddly, linux-scsi wasn't on the original
> > mail for this series summary.)
> > 
> Sorry I missed the scsi lists on the summary patch.
> 
> While browsing the code I found another spot in mmc layer which
> needs fixing. The patch is at the end of the email with Chris
> and linux-mmc cc'ed here.

Would you mind putting them all in the patch system, I can add the acks
should anyone supply them later, and I'll repost them along with my set
of dma-mask patches.  Thanks.

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Santosh Shilimkar]

On Monday 29 July 2013 07:15 AM, Russell King - ARM Linux wrote:
> On Fri, Jul 26, 2013 at 12:28:26PM -0400, Santosh Shilimkar wrote:
>> On Friday 26 July 2013 11:10 AM, Russell King - ARM Linux wrote:
>>> On Fri, Jul 12, 2013 at 05:48:09PM -0400, Santosh Shilimkar wrote:
>>>> The series is an attempt to move ARM port to NO_BOOTMEM. As discussed
>>>> on list NO_BOOTMEM move needed updates to max*pfn meaning to be maximum
>>>> PFNs but that breaks the dma_mask for few block layer drivers since
>>>> ARM start of physical memory is not PFN0 unlike most of the architectures.
>>>> Some more read on it is here:
>>>> 	http://lwn.net/Articles/543408/
>>>> 	http://lwn.net/Articles/543424/
>>>>
>>>> To address this issue, we introduce generic dma_max_pfn() helper which
>>>> can be overridden from the architectures.
>>>> 	
>>>> Another intention behind move to nobootmem is also to convert ARM to
>>>> switch to memblock and getting rid of bootmem allocator dependency which
>>>> don't work for LPAE machines which has physical memory starting beyond
>>>> 4 GB boundary. It needs changes to core kernel and also a new memblock
>>>> API. More on this can be found here:
>>>> 	https://lkml.org/lkml/2013/6/29/77
>>>>
>>>> I have been trying to cook up these patches with kind help from Russell
>>>> and we know series don't solve all the dma_mask bad assumptions. But at
>>>> least I am hoping that it can get the ball rolling.	
>>>>
>>>> Comments/testing help is welcome !!
>>>
>>> As this is related to some of the cleanup of dma_mask which I've been
>>> doing, I think it may make sense to roll this into one tree.  Any
>>> objection to that?
>>>
>>> Can we get any acks on this stuff from Jens and Jejb etc - especially
>>> for the bits which touch block/ and for the scsi bits as these are
>>> touching other subsystems.  (oddly, linux-scsi wasn't on the original
>>> mail for this series summary.)
>>>
>> Sorry I missed the scsi lists on the summary patch.
>>
>> While browsing the code I found another spot in mmc layer which
>> needs fixing. The patch is at the end of the email with Chris
>> and linux-mmc cc'ed here.
> 
> Would you mind putting them all in the patch system, I can add the acks
> should anyone supply them later, and I'll repost them along with my set
> of dma-mask patches.  Thanks.
> 
Done.
7794/1, 7795/1, 7796/1, 7797/1, 7798/1, 7799/1

Didn't know how to get XXXX/1,2,3,4... pushed into the tracker.
BTW, I have also pushed the patched on my git tree branch [1] just
in case you or some one needs it.

Regards,
Santosh
[1] git://git.kernel.org/pub/scm/linux/kernel/git/ssantosh/linux-keystone.git
3.12/nobootmem_n_dma-mask

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Russell King - ARM Linux]

On Mon, Jul 29, 2013 at 09:26:44AM -0400, Santosh Shilimkar wrote:
> On Monday 29 July 2013 07:15 AM, Russell King - ARM Linux wrote:
> > Would you mind putting them all in the patch system, I can add the acks
> > should anyone supply them later, and I'll repost them along with my set
> > of dma-mask patches.  Thanks.
> > 
> Done.
> 7794/1, 7795/1, 7796/1, 7797/1, 7798/1, 7799/1
> 
> Didn't know how to get XXXX/1,2,3,4... pushed into the tracker.
> BTW, I have also pushed the patched on my git tree branch [1] just
> in case you or some one needs it.

Thanks.  I'd prefer not to have them as stable commits yet because should
we get acks from Jens, Jejb or cjb, we will need to add their acks to them.

My dma-masks branch is still very much unstable at the moment (which is
why its not published) but I shall be posting the patches during this
week.

Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

[Santosh Shilimkar]

On Monday 29 July 2013 09:40 AM, Russell King - ARM Linux wrote:
> On Mon, Jul 29, 2013 at 09:26:44AM -0400, Santosh Shilimkar wrote:
>> On Monday 29 July 2013 07:15 AM, Russell King - ARM Linux wrote:
>>> Would you mind putting them all in the patch system, I can add the acks
>>> should anyone supply them later, and I'll repost them along with my set
>>> of dma-mask patches.  Thanks.
>>>
>> Done.
>> 7794/1, 7795/1, 7796/1, 7797/1, 7798/1, 7799/1
>>
>> Didn't know how to get XXXX/1,2,3,4... pushed into the tracker.
>> BTW, I have also pushed the patched on my git tree branch [1] just
>> in case you or some one needs it.
> 
> Thanks.  I'd prefer not to have them as stable commits yet because should
> we get acks from Jens, Jejb or cjb, we will need to add their acks to them.
>
right.
 
> My dma-masks branch is still very much unstable at the moment (which is
> why its not published) but I shall be posting the patches during this
> week.
> 
Sure.

Regards,
Santosh