Re: [PATCH v3 2/7] drm/ttm: Add ttm_kmap_obj_to_dma_buf_map() for type conversion

Christian König
2020-09-30T08:34:42Z

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Am 30.09.20 um 10:19 schrieb Thomas Zimmermann:
> Hi
>
> Am 30.09.20 um 10:05 schrieb Christian König:
>> Am 29.09.20 um 19:49 schrieb Thomas Zimmermann:
>>> Hi Christian
>>>
>>> Am 29.09.20 um 17:35 schrieb Christian König:
>>>> Am 29.09.20 um 17:14 schrieb Thomas Zimmermann:
>>>>> The new helper ttm_kmap_obj_to_dma_buf() extracts address and location
>>>>> from and instance of TTM's kmap_obj and initializes struct dma_buf_map
>>>>> with these values. Helpful for TTM-based drivers.
>>>> We could completely drop that if we use the same structure inside TTM as
>>>> well.
>>>>
>>>> Additional to that which driver is going to use this?
>>> As Daniel mentioned, it's in patch 3. The TTM-based drivers will
>>> retrieve the pointer via this function.
>>>
>>> I do want to see all that being more tightly integrated into TTM, but
>>> not in this series. This one is about fixing the bochs-on-sparc64
>>> problem for good. Patch 7 adds an update to TTM to the DRM TODO list.
>> I should have asked which driver you try to fix here :)
>>
>> In this case just keep the function inside bochs and only fix it there.
>>
>> All other drivers can be fixed when we generally pump this through TTM.
> Did you take a look at patch 3? This function will be used by VRAM
> helpers, nouveau, radeon, amdgpu and qxl. If we don't put it here, we
> have to duplicate the functionality in each if these drivers. Bochs
> itself uses VRAM helpers and doesn't touch the function directly.

Ah, ok can we have that then only in the VRAM helpers?

Alternative you could go ahead and use dma_buf_map in ttm_bo_kmap_obj
directly and drop the hack with the TTM_BO_MAP_IOMEM_MASK.

What I want to avoid is to have another conversion function in TTM
because what happens here is that we already convert from
ttm_bus_placement to ttm_bo_kmap_obj and then to dma_buf_map.

Thanks,
Christian.

>
> Best regards
> Thomas
>
>> Regards,
>> Christian.
>>
>>> Best regards
>>> Thomas
>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>>>>> ---
>>>>>   include/drm/ttm/ttm_bo_api.h | 24 ++++++++++++++++++++++++
>>>>>   include/linux/dma-buf-map.h  | 20 ++++++++++++++++++++
>>>>>   2 files changed, 44 insertions(+)
>>>>>
>>>>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>>>>> index c96a25d571c8..62d89f05a801 100644
>>>>> --- a/include/drm/ttm/ttm_bo_api.h
>>>>> +++ b/include/drm/ttm/ttm_bo_api.h
>>>>> @@ -34,6 +34,7 @@
>>>>>   #include <drm/drm_gem.h>
>>>>>   #include <drm/drm_hashtab.h>
>>>>>   #include <drm/drm_vma_manager.h>
>>>>> +#include <linux/dma-buf-map.h>
>>>>>   #include <linux/kref.h>
>>>>>   #include <linux/list.h>
>>>>>   #include <linux/wait.h>
>>>>> @@ -486,6 +487,29 @@ static inline void *ttm_kmap_obj_virtual(struct
>>>>> ttm_bo_kmap_obj *map,
>>>>>       return map->virtual;
>>>>>   }
>>>>>   +/**
>>>>> + * ttm_kmap_obj_to_dma_buf_map
>>>>> + *
>>>>> + * @kmap: A struct ttm_bo_kmap_obj returned from ttm_bo_kmap.
>>>>> + * @map: Returns the mapping as struct dma_buf_map
>>>>> + *
>>>>> + * Converts struct ttm_bo_kmap_obj to struct dma_buf_map. If the memory
>>>>> + * is not mapped, the returned mapping is initialized to NULL.
>>>>> + */
>>>>> +static inline void ttm_kmap_obj_to_dma_buf_map(struct ttm_bo_kmap_obj
>>>>> *kmap,
>>>>> +                           struct dma_buf_map *map)
>>>>> +{
>>>>> +    bool is_iomem;
>>>>> +    void *vaddr = ttm_kmap_obj_virtual(kmap, &is_iomem);
>>>>> +
>>>>> +    if (!vaddr)
>>>>> +        dma_buf_map_clear(map);
>>>>> +    else if (is_iomem)
>>>>> +        dma_buf_map_set_vaddr_iomem(map, (void __force __iomem *)vaddr);
>>>>> +    else
>>>>> +        dma_buf_map_set_vaddr(map, vaddr);
>>>>> +}
>>>>> +
>>>>>   /**
>>>>>    * ttm_bo_kmap
>>>>>    *
>>>>> diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h
>>>>> index fd1aba545fdf..2e8bbecb5091 100644
>>>>> --- a/include/linux/dma-buf-map.h
>>>>> +++ b/include/linux/dma-buf-map.h
>>>>> @@ -45,6 +45,12 @@
>>>>>    *
>>>>>    *    dma_buf_map_set_vaddr(&map. 0xdeadbeaf);
>>>>>    *
>>>>> + * To set an address in I/O memory, use dma_buf_map_set_vaddr_iomem().
>>>>> + *
>>>>> + * .. code-block:: c
>>>>> + *
>>>>> + *    dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf);
>>>>> + *
>>>>>    * Test if a mapping is valid with either dma_buf_map_is_set() or
>>>>>    * dma_buf_map_is_null().
>>>>>    *
>>>>> @@ -118,6 +124,20 @@ static inline void dma_buf_map_set_vaddr(struct
>>>>> dma_buf_map *map, void *vaddr)
>>>>>       map->is_iomem = false;
>>>>>   }
>>>>>   +/**
>>>>> + * dma_buf_map_set_vaddr_iomem - Sets a dma-buf mapping structure to
>>>>> an address in I/O memory
>>>>> + * @map:        The dma-buf mapping structure
>>>>> + * @vaddr_iomem:    An I/O-memory address
>>>>> + *
>>>>> + * Sets the address and the I/O-memory flag.
>>>>> + */
>>>>> +static inline void dma_buf_map_set_vaddr_iomem(struct dma_buf_map *map,
>>>>> +                           void __iomem *vaddr_iomem)
>>>>> +{
>>>>> +    map->vaddr_iomem = vaddr_iomem;
>>>>> +    map->is_iomem = true;
>>>>> +}
>>>>> +
>>>>>   /**
>>>>>    * dma_buf_map_is_equal - Compares two dma-buf mapping structures
>>>>> for equality
>>>>>    * @lhs:    The dma-buf mapping structure
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