Re: [PATCH v4 05/10] drm/ttm: Add vmap/vunmap to TTM and TTM GEM helpers

["Christian König" <christian.koenig@amd.com>]

Hi Thomas,

[SNIP]
>>>    +int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map)
>>> +{
>>> +    struct ttm_resource *mem = &bo->mem;
>>> +    int ret;
>>> +
>>> +    ret = ttm_mem_io_reserve(bo->bdev, mem);
>>> +    if (ret)
>>> +        return ret;
>>> +
>>> +    if (mem->bus.is_iomem) {
>>> +        void __iomem *vaddr_iomem;
>>> +        unsigned long size = bo->num_pages << PAGE_SHIFT;
>> Please use uint64_t here and make sure to cast bo->num_pages before
>> shifting.
> I thought the rule of thumb is to use u64 in source code. Yet TTM only
> uses uint*_t types. Is there anything special about TTM?

My last status is that you can use both and my personal preference is to 
use the uint*_t types because they are part of a higher level standard.

>> We have an unit tests of allocating a 8GB BO and that should work on a
>> 32bit machine as well :)
>>
>>> +
>>> +        if (mem->bus.addr)
>>> +            vaddr_iomem = (void *)(((u8 *)mem->bus.addr));
> I after reading the patch again, I realized that this is the
> 'ttm_bo_map_premapped' case and it's missing from _vunmap(). I see two
> options here: ignore this case in _vunmap(), or do an ioremap()
> unconditionally. Which one is preferable?

ioremap would be very very bad, so we should just do nothing.

Thanks,
Christian.

>
> Best regards
> Thomas
>
>>> +        else if (mem->placement & TTM_PL_FLAG_WC)
>> I've just nuked the TTM_PL_FLAG_WC flag in drm-misc-next. There is a new
>> mem->bus.caching enum as replacement.
>>
>>> +            vaddr_iomem = ioremap_wc(mem->bus.offset, size);
>>> +        else
>>> +            vaddr_iomem = ioremap(mem->bus.offset, size);
>>> +
>>> +        if (!vaddr_iomem)
>>> +            return -ENOMEM;
>>> +
>>> +        dma_buf_map_set_vaddr_iomem(map, vaddr_iomem);
>>> +
>>> +    } else {
>>> +        struct ttm_operation_ctx ctx = {
>>> +            .interruptible = false,
>>> +            .no_wait_gpu = false
>>> +        };
>>> +        struct ttm_tt *ttm = bo->ttm;
>>> +        pgprot_t prot;
>>> +        void *vaddr;
>>> +
>>> +        BUG_ON(!ttm);
>> I think we can drop this, populate will just crash badly anyway.
>>
>>> +
>>> +        ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
>>> +        if (ret)
>>> +            return ret;
>>> +
>>> +        /*
>>> +         * We need to use vmap to get the desired page protection
>>> +         * or to make the buffer object look contiguous.
>>> +         */
>>> +        prot = ttm_io_prot(mem->placement, PAGE_KERNEL);
>> The calling convention has changed on drm-misc-next as well, but should
>> be trivial to adapt.
>>
>> Regards,
>> Christian.
>>
>>> +        vaddr = vmap(ttm->pages, bo->num_pages, 0, prot);
>>> +        if (!vaddr)
>>> +            return -ENOMEM;
>>> +
>>> +        dma_buf_map_set_vaddr(map, vaddr);
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +EXPORT_SYMBOL(ttm_bo_vmap);
>>> +
>>> +void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct dma_buf_map
>>> *map)
>>> +{
>>> +    if (dma_buf_map_is_null(map))
>>> +        return;
>>> +
>>> +    if (map->is_iomem)
>>> +        iounmap(map->vaddr_iomem);
>>> +    else
>>> +        vunmap(map->vaddr);
>>> +    dma_buf_map_clear(map);
>>> +
>>> +    ttm_mem_io_free(bo->bdev, &bo->mem);
>>> +}
>>> +EXPORT_SYMBOL(ttm_bo_vunmap);
>>> +
>>>    static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
>>>                     bool dst_use_tt)
>>>    {
>>> diff --git a/include/drm/drm_gem_ttm_helper.h
>>> b/include/drm/drm_gem_ttm_helper.h
>>> index 118cef76f84f..7c6d874910b8 100644
>>> --- a/include/drm/drm_gem_ttm_helper.h
>>> +++ b/include/drm/drm_gem_ttm_helper.h
>>> @@ -10,11 +10,17 @@
>>>    #include <drm/ttm/ttm_bo_api.h>
>>>    #include <drm/ttm/ttm_bo_driver.h>
>>>    +struct dma_buf_map;
>>> +
>>>    #define drm_gem_ttm_of_gem(gem_obj) \
>>>        container_of(gem_obj, struct ttm_buffer_object, base)
>>>      void drm_gem_ttm_print_info(struct drm_printer *p, unsigned int
>>> indent,
>>>                    const struct drm_gem_object *gem);
>>> +int drm_gem_ttm_vmap(struct drm_gem_object *gem,
>>> +             struct dma_buf_map *map);
>>> +void drm_gem_ttm_vunmap(struct drm_gem_object *gem,
>>> +            struct dma_buf_map *map);
>>>    int drm_gem_ttm_mmap(struct drm_gem_object *gem,
>>>                 struct vm_area_struct *vma);
>>>    diff --git a/include/drm/ttm/ttm_bo_api.h
>>> b/include/drm/ttm/ttm_bo_api.h
>>> index 37102e45e496..2c59a785374c 100644
>>> --- a/include/drm/ttm/ttm_bo_api.h
>>> +++ b/include/drm/ttm/ttm_bo_api.h
>>> @@ -48,6 +48,8 @@ struct ttm_bo_global;
>>>      struct ttm_bo_device;
>>>    +struct dma_buf_map;
>>> +
>>>    struct drm_mm_node;
>>>      struct ttm_placement;
>>> @@ -494,6 +496,32 @@ int ttm_bo_kmap(struct ttm_buffer_object *bo,
>>> unsigned long start_page,
>>>     */
>>>    void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
>>>    +/**
>>> + * ttm_bo_vmap
>>> + *
>>> + * @bo: The buffer object.
>>> + * @map: pointer to a struct dma_buf_map representing the map.
>>> + *
>>> + * Sets up a kernel virtual mapping, using ioremap or vmap to the
>>> + * data in the buffer object. The parameter @map returns the virtual
>>> + * address as struct dma_buf_map. Unmap the buffer with ttm_bo_vunmap().
>>> + *
>>> + * Returns
>>> + * -ENOMEM: Out of memory.
>>> + * -EINVAL: Invalid range.
>>> + */
>>> +int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map);
>>> +
>>> +/**
>>> + * ttm_bo_vunmap
>>> + *
>>> + * @bo: The buffer object.
>>> + * @map: Object describing the map to unmap.
>>> + *
>>> + * Unmaps a kernel map set up by ttm_bo_vmap().
>>> + */
>>> +void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct dma_buf_map
>>> *map);
>>> +
>>>    /**
>>>     * ttm_bo_mmap_obj - mmap memory backed by a ttm buffer object.
>>>     *
>>> 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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