2022-07-25 15:10:04

by Bob Beckett

[permalink] [raw]
Subject: [PATCH v4] drm/i915: stop using swiotlb

Calling swiotlb functions directly is nowadays considered harmful. See
https://lore.kernel.org/intel-gfx/[email protected]/

Replace swiotlb_max_segment() calls with dma_max_mapping_size().
In i915_gem_object_get_pages_internal() no longer consider max_segment
only if CONFIG_SWIOTLB is enabled. There can be other (iommu related)
causes of specific max segment sizes.

Cc: Christoph Hellwig <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Thomas Hellstrom <[email protected]>
Cc: Matthew Auld <[email protected]>

v2: - restore UINT_MAX clamp in i915_sg_segment_size()
- drop PAGE_SIZE check as it will always be >= PAGE_SIZE
v3: - actually clamp to UINT_MAX in i915_sg_segment_size()
v4: - round down max segment size to PAGE_SIZE

Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Tvrtko Ursulin <[email protected]>
Signed-off-by: Robert Beckett <[email protected]>
---
drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 ++++---------------
drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 2 +-
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 4 ++--
drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 2 +-
drivers/gpu/drm/i915/i915_scatterlist.h | 17 ++++-------------
5 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
index c698f95af15f..24f37658f1bb 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
@@ -6,7 +6,6 @@

#include <linux/scatterlist.h>
#include <linux/slab.h>
-#include <linux/swiotlb.h>

#include "i915_drv.h"
#include "i915_gem.h"
@@ -38,22 +37,12 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
struct scatterlist *sg;
unsigned int sg_page_sizes;
unsigned int npages;
- int max_order;
+ int max_order = MAX_ORDER;
+ unsigned int max_segment;
gfp_t gfp;

- max_order = MAX_ORDER;
-#ifdef CONFIG_SWIOTLB
- if (is_swiotlb_active(obj->base.dev->dev)) {
- unsigned int max_segment;
-
- max_segment = swiotlb_max_segment();
- if (max_segment) {
- max_segment = max_t(unsigned int, max_segment,
- PAGE_SIZE) >> PAGE_SHIFT;
- max_order = min(max_order, ilog2(max_segment));
- }
- }
-#endif
+ max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT;
+ max_order = min(max_order, ilog2(max_segment));

gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
if (IS_I965GM(i915) || IS_I965G(i915)) {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index 4eed3dd90ba8..34b9c76cd8e6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -194,7 +194,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
struct intel_memory_region *mem = obj->mm.region;
struct address_space *mapping = obj->base.filp->f_mapping;
const unsigned long page_count = obj->base.size / PAGE_SIZE;
- unsigned int max_segment = i915_sg_segment_size();
+ unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
struct sg_table *st;
struct sgt_iter sgt_iter;
struct page *page;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 5a5cf332d8a5..7a828c9c0f6d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- const unsigned int max_segment = i915_sg_segment_size();
+ const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
struct file *filp = i915_tt->filp;
struct sgt_iter sgt_iter;
@@ -568,7 +568,7 @@ static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
ret = sg_alloc_table_from_pages_segment(st,
ttm->pages, ttm->num_pages,
0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
- i915_sg_segment_size(), GFP_KERNEL);
+ i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
if (ret) {
st->sgl = NULL;
return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 094f06b4ce33..dfc35905dba2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -129,7 +129,7 @@ static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
{
const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
- unsigned int max_segment = i915_sg_segment_size();
+ unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev);
struct sg_table *st;
unsigned int sg_page_sizes;
struct page **pvec;
diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
index 9ddb3e743a3e..1377a97a20cf 100644
--- a/drivers/gpu/drm/i915/i915_scatterlist.h
+++ b/drivers/gpu/drm/i915/i915_scatterlist.h
@@ -9,7 +9,7 @@

#include <linux/pfn.h>
#include <linux/scatterlist.h>
-#include <linux/swiotlb.h>
+#include <linux/dma-mapping.h>

#include "i915_gem.h"

@@ -127,19 +127,10 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg)
return page_sizes;
}

-static inline unsigned int i915_sg_segment_size(void)
+static inline unsigned int i915_sg_segment_size(struct device *dev)
{
- unsigned int size = swiotlb_max_segment();
-
- if (size == 0)
- size = UINT_MAX;
-
- size = rounddown(size, PAGE_SIZE);
- /* swiotlb_max_segment_size can return 1 byte when it means one page. */
- if (size < PAGE_SIZE)
- size = PAGE_SIZE;
-
- return size;
+ size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));
+ return round_down(max, PAGE_SIZE);
}

bool i915_sg_trim(struct sg_table *orig_st);
--
2.25.1


2022-07-26 13:29:42

by Tvrtko Ursulin

[permalink] [raw]
Subject: Re: [PATCH v4] drm/i915: stop using swiotlb


On 25/07/2022 15:18, Robert Beckett wrote:
> Calling swiotlb functions directly is nowadays considered harmful. See
> https://lore.kernel.org/intel-gfx/[email protected]/
>
> Replace swiotlb_max_segment() calls with dma_max_mapping_size().
> In i915_gem_object_get_pages_internal() no longer consider max_segment
> only if CONFIG_SWIOTLB is enabled. There can be other (iommu related)
> causes of specific max segment sizes.
>
> Cc: Christoph Hellwig <[email protected]>
> Cc: Tvrtko Ursulin <[email protected]>
> Cc: Thomas Hellstrom <[email protected]>
> Cc: Matthew Auld <[email protected]>
>
> v2: - restore UINT_MAX clamp in i915_sg_segment_size()
> - drop PAGE_SIZE check as it will always be >= PAGE_SIZE
> v3: - actually clamp to UINT_MAX in i915_sg_segment_size()
> v4: - round down max segment size to PAGE_SIZE
>
> Reviewed-by: Christoph Hellwig <[email protected]>
> Reviewed-by: Tvrtko Ursulin <[email protected]>
> Signed-off-by: Robert Beckett <[email protected]>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 ++++---------------
> drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 4 ++--
> drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 2 +-
> drivers/gpu/drm/i915/i915_scatterlist.h | 17 ++++-------------
> 5 files changed, 12 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
> index c698f95af15f..24f37658f1bb 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
> @@ -6,7 +6,6 @@
>
> #include <linux/scatterlist.h>
> #include <linux/slab.h>
> -#include <linux/swiotlb.h>
>
> #include "i915_drv.h"
> #include "i915_gem.h"
> @@ -38,22 +37,12 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
> struct scatterlist *sg;
> unsigned int sg_page_sizes;
> unsigned int npages;
> - int max_order;
> + int max_order = MAX_ORDER;
> + unsigned int max_segment;
> gfp_t gfp;
>
> - max_order = MAX_ORDER;
> -#ifdef CONFIG_SWIOTLB
> - if (is_swiotlb_active(obj->base.dev->dev)) {
> - unsigned int max_segment;
> -
> - max_segment = swiotlb_max_segment();
> - if (max_segment) {
> - max_segment = max_t(unsigned int, max_segment,
> - PAGE_SIZE) >> PAGE_SHIFT;
> - max_order = min(max_order, ilog2(max_segment));
> - }
> - }
> -#endif
> + max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT;
> + max_order = min(max_order, ilog2(max_segment));
>
> gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
> if (IS_I965GM(i915) || IS_I965G(i915)) {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index 4eed3dd90ba8..34b9c76cd8e6 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> @@ -194,7 +194,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> struct intel_memory_region *mem = obj->mm.region;
> struct address_space *mapping = obj->base.filp->f_mapping;
> const unsigned long page_count = obj->base.size / PAGE_SIZE;
> - unsigned int max_segment = i915_sg_segment_size();
> + unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> struct sg_table *st;
> struct sgt_iter sgt_iter;
> struct page *page;
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 5a5cf332d8a5..7a828c9c0f6d 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
> struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
> struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
> struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
> - const unsigned int max_segment = i915_sg_segment_size();
> + const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
> struct file *filp = i915_tt->filp;
> struct sgt_iter sgt_iter;
> @@ -568,7 +568,7 @@ static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
> ret = sg_alloc_table_from_pages_segment(st,
> ttm->pages, ttm->num_pages,
> 0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
> - i915_sg_segment_size(), GFP_KERNEL);
> + i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
> if (ret) {
> st->sgl = NULL;
> return ERR_PTR(ret);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 094f06b4ce33..dfc35905dba2 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -129,7 +129,7 @@ static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
> static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
> {
> const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
> - unsigned int max_segment = i915_sg_segment_size();
> + unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev);
> struct sg_table *st;
> unsigned int sg_page_sizes;
> struct page **pvec;
> diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
> index 9ddb3e743a3e..1377a97a20cf 100644
> --- a/drivers/gpu/drm/i915/i915_scatterlist.h
> +++ b/drivers/gpu/drm/i915/i915_scatterlist.h
> @@ -9,7 +9,7 @@
>
> #include <linux/pfn.h>
> #include <linux/scatterlist.h>
> -#include <linux/swiotlb.h>
> +#include <linux/dma-mapping.h>
>
> #include "i915_gem.h"
>
> @@ -127,19 +127,10 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg)
> return page_sizes;
> }
>
> -static inline unsigned int i915_sg_segment_size(void)
> +static inline unsigned int i915_sg_segment_size(struct device *dev)
> {
> - unsigned int size = swiotlb_max_segment();
> -
> - if (size == 0)
> - size = UINT_MAX;
> -
> - size = rounddown(size, PAGE_SIZE);
> - /* swiotlb_max_segment_size can return 1 byte when it means one page. */
> - if (size < PAGE_SIZE)
> - size = PAGE_SIZE;
> -
> - return size;
> + size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));

Hope your patience is not growing thin but blank line here as per
checkpatch. I could fudge when applying though.

Otherwise it finally passed CI, yay! Now do we dig deeper to a)
understand how/where it failed and b) check what are the possible return
values from dma_max_mapping_size(), or call it done?

Regards,

Tvrtko

> + return round_down(max, PAGE_SIZE);
> }
>
> bool i915_sg_trim(struct sg_table *orig_st);

2022-07-26 15:36:05

by Bob Beckett

[permalink] [raw]
Subject: Re: [PATCH v4] drm/i915: stop using swiotlb



On 26/07/2022 14:12, Tvrtko Ursulin wrote:
>
> On 25/07/2022 15:18, Robert Beckett wrote:
>> Calling swiotlb functions directly is nowadays considered harmful. See
>> https://lore.kernel.org/intel-gfx/[email protected]/
>>
>> Replace swiotlb_max_segment() calls with dma_max_mapping_size().
>> In i915_gem_object_get_pages_internal() no longer consider max_segment
>> only if CONFIG_SWIOTLB is enabled. There can be other (iommu related)
>> causes of specific max segment sizes.
>>
>> Cc: Christoph Hellwig <[email protected]>
>> Cc: Tvrtko Ursulin <[email protected]>
>> Cc: Thomas Hellstrom <[email protected]>
>> Cc: Matthew Auld <[email protected]>
>>
>> v2: - restore UINT_MAX clamp in i915_sg_segment_size()
>>      - drop PAGE_SIZE check as it will always be >= PAGE_SIZE
>> v3: - actually clamp to UINT_MAX in i915_sg_segment_size()
>> v4: - round down max segment size to PAGE_SIZE
>>
>> Reviewed-by: Christoph Hellwig <[email protected]>
>> Reviewed-by: Tvrtko Ursulin <[email protected]>
>> Signed-off-by: Robert Beckett <[email protected]>
>> ---
>>   drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 ++++---------------
>>   drivers/gpu/drm/i915/gem/i915_gem_shmem.c    |  2 +-
>>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c      |  4 ++--
>>   drivers/gpu/drm/i915/gem/i915_gem_userptr.c  |  2 +-
>>   drivers/gpu/drm/i915/i915_scatterlist.h      | 17 ++++-------------
>>   5 files changed, 12 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> index c698f95af15f..24f37658f1bb 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
>> @@ -6,7 +6,6 @@
>>   #include <linux/scatterlist.h>
>>   #include <linux/slab.h>
>> -#include <linux/swiotlb.h>
>>   #include "i915_drv.h"
>>   #include "i915_gem.h"
>> @@ -38,22 +37,12 @@ static int
>> i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
>>       struct scatterlist *sg;
>>       unsigned int sg_page_sizes;
>>       unsigned int npages;
>> -    int max_order;
>> +    int max_order = MAX_ORDER;
>> +    unsigned int max_segment;
>>       gfp_t gfp;
>> -    max_order = MAX_ORDER;
>> -#ifdef CONFIG_SWIOTLB
>> -    if (is_swiotlb_active(obj->base.dev->dev)) {
>> -        unsigned int max_segment;
>> -
>> -        max_segment = swiotlb_max_segment();
>> -        if (max_segment) {
>> -            max_segment = max_t(unsigned int, max_segment,
>> -                        PAGE_SIZE) >> PAGE_SHIFT;
>> -            max_order = min(max_order, ilog2(max_segment));
>> -        }
>> -    }
>> -#endif
>> +    max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT;
>> +    max_order = min(max_order, ilog2(max_segment));
>>       gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
>>       if (IS_I965GM(i915) || IS_I965G(i915)) {
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
>> index 4eed3dd90ba8..34b9c76cd8e6 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
>> @@ -194,7 +194,7 @@ static int shmem_get_pages(struct
>> drm_i915_gem_object *obj)
>>       struct intel_memory_region *mem = obj->mm.region;
>>       struct address_space *mapping = obj->base.filp->f_mapping;
>>       const unsigned long page_count = obj->base.size / PAGE_SIZE;
>> -    unsigned int max_segment = i915_sg_segment_size();
>> +    unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
>>       struct sg_table *st;
>>       struct sgt_iter sgt_iter;
>>       struct page *page;
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> index 5a5cf332d8a5..7a828c9c0f6d 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> @@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct
>> ttm_device *bdev,
>>       struct drm_i915_private *i915 = container_of(bdev,
>> typeof(*i915), bdev);
>>       struct intel_memory_region *mr =
>> i915->mm.regions[INTEL_MEMORY_SYSTEM];
>>       struct i915_ttm_tt *i915_tt = container_of(ttm,
>> typeof(*i915_tt), ttm);
>> -    const unsigned int max_segment = i915_sg_segment_size();
>> +    const unsigned int max_segment =
>> i915_sg_segment_size(i915->drm.dev);
>>       const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
>>       struct file *filp = i915_tt->filp;
>>       struct sgt_iter sgt_iter;
>> @@ -568,7 +568,7 @@ static struct i915_refct_sgt
>> *i915_ttm_tt_get_st(struct ttm_tt *ttm)
>>       ret = sg_alloc_table_from_pages_segment(st,
>>               ttm->pages, ttm->num_pages,
>>               0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
>> -            i915_sg_segment_size(), GFP_KERNEL);
>> +            i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
>>       if (ret) {
>>           st->sgl = NULL;
>>           return ERR_PTR(ret);
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> index 094f06b4ce33..dfc35905dba2 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
>> @@ -129,7 +129,7 @@ static void
>> i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
>>   static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
>>   {
>>       const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
>> -    unsigned int max_segment = i915_sg_segment_size();
>> +    unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev);
>>       struct sg_table *st;
>>       unsigned int sg_page_sizes;
>>       struct page **pvec;
>> diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h
>> b/drivers/gpu/drm/i915/i915_scatterlist.h
>> index 9ddb3e743a3e..1377a97a20cf 100644
>> --- a/drivers/gpu/drm/i915/i915_scatterlist.h
>> +++ b/drivers/gpu/drm/i915/i915_scatterlist.h
>> @@ -9,7 +9,7 @@
>>   #include <linux/pfn.h>
>>   #include <linux/scatterlist.h>
>> -#include <linux/swiotlb.h>
>> +#include <linux/dma-mapping.h>
>>   #include "i915_gem.h"
>> @@ -127,19 +127,10 @@ static inline unsigned int
>> i915_sg_dma_sizes(struct scatterlist *sg)
>>       return page_sizes;
>>   }
>> -static inline unsigned int i915_sg_segment_size(void)
>> +static inline unsigned int i915_sg_segment_size(struct device *dev)
>>   {
>> -    unsigned int size = swiotlb_max_segment();
>> -
>> -    if (size == 0)
>> -        size = UINT_MAX;
>> -
>> -    size = rounddown(size, PAGE_SIZE);
>> -    /* swiotlb_max_segment_size can return 1 byte when it means one
>> page. */
>> -    if (size < PAGE_SIZE)
>> -        size = PAGE_SIZE;
>> -
>> -    return size;
>> +    size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));
>
> Hope your patience is not growing thin but blank line here as per
> checkpatch. I could fudge when applying though.

no worries, I'll issue a new version shortly.
I only recently guided a mentee to "always do your checkpatch, even if
only doing a quick 1 character change, you never know if it you make a
small mistake"
I guess do as I say, not as I do applies here :)

>
> Otherwise it finally passed CI, yay! Now do we dig deeper to a)
> understand how/where it failed and b) check what are the possible return
> values from dma_max_mapping_size(), or call it done?

I will have to call it done myself as I am unable to repo it locally.
I could spend a lot of time debugging it via trybot, but I expect it
will be easier, quicker and cheaper to get someone with local hw with a
repro case to debug it if you want to root cause it.

>
> Regards,
>
> Tvrtko
>
>> +    return round_down(max, PAGE_SIZE);
>>   }
>>   bool i915_sg_trim(struct sg_table *orig_st);