Re: [PATCH] drm/ttm: device address space != CPU address space

[Thomas Hellstrom <thellstrom@vmware.com>]

Hi!

IIRC, the interpretation of gpu_offset is fully controlled by the
driver. That means to keep a native integer size
you should be able to set

radeon_gpu_offset := (ttm_gpu_offset << suitable_shift);

However, if you feel that this is too intrusive in the driver, I'm not
against the current patch as it stands. It's important, however that the
interactions with drm_mm is sorted out. I'm not sure the patch that
converted drm_mm to 64-bit instead
of unsigned long went in. (There were similar arguments against that patch).

Thanks,
Thomas


On 03/04/2015 06:18 AM, Alex Deucher wrote:
> We need to store device offsets in 64 bit as the device
> address space may be larger than the CPU's.
>
> Fixes GPU init failures on radeons with 4GB or more of
> vram on 32 bit kernels.  We put vram at the start of the
> GPU's address space so the gart aperture starts at 4 GB
> causing all GPU addresses in the gart aperture to get
> truncated.
>
> bug:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D89072&d=AwIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=M1rvbqZd6hlmRIsZmBXhSypX4cSQqZSddym13SRVKtg&s=sriG7bnxL46LbaYmq_FnswHY9WOrPvTbdK7um05zoxE&e= 
>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> Cc: thellstrom@vmware.com
> ---
> Untested.  Someone more familiar with the ttm internals can
> probably point out any additional bits I missed.  Heading to
> bed now.
>
>  drivers/gpu/drm/ttm/ttm_bo.c    | 2 +-
>  include/drm/ttm/ttm_bo_api.h    | 2 +-
>  include/drm/ttm/ttm_bo_driver.h | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index d395b0b..8d9b7de 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -74,7 +74,7 @@ static void ttm_mem_type_debug(struct ttm_bo_device *bdev, int mem_type)
>  	pr_err("    has_type: %d\n", man->has_type);
>  	pr_err("    use_type: %d\n", man->use_type);
>  	pr_err("    flags: 0x%08X\n", man->flags);
> -	pr_err("    gpu_offset: 0x%08lX\n", man->gpu_offset);
> +	pr_err("    gpu_offset: 0x%08llX\n", man->gpu_offset);
>  	pr_err("    size: %llu\n", man->size);
>  	pr_err("    available_caching: 0x%08X\n", man->available_caching);
>  	pr_err("    default_caching: 0x%08X\n", man->default_caching);
> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> index 0ccf7f2..c768ddf 100644
> --- a/include/drm/ttm/ttm_bo_api.h
> +++ b/include/drm/ttm/ttm_bo_api.h
> @@ -249,7 +249,7 @@ struct ttm_buffer_object {
>  	 * either of these locks held.
>  	 */
>  
> -	unsigned long offset;
> +	uint64_t offset; /* GPU address space is independent of CPU word size */
>  	uint32_t cur_placement;
>  
>  	struct sg_table *sg;
> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
> index 142d752..813042c 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -277,7 +277,7 @@ struct ttm_mem_type_manager {
>  	bool has_type;
>  	bool use_type;
>  	uint32_t flags;
> -	unsigned long gpu_offset;
> +	uint64_t gpu_offset; /* GPU address space is independent of CPU word size */
>  	uint64_t size;
>  	uint32_t available_caching;
>  	uint32_t default_caching;

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