[PATCH v2 3/5] drm/xe/display: Avoid calling readq()

[Matt Roper]

On Tue, Jan 16, 2024 at 09:40:48AM -0800, Lucas De Marchi wrote:
> readq() is not available in 32bits. iosys-map already has the logic in
> place to use read u64 in all cases, so simply add a helper variable for
> using that.
> 
> Fixes: 44e694958b95 ("drm/xe/display: Implement display support")
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>  .../gpu/drm/xe/compat-i915-headers/gem/i915_gem_object.h   | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/compat-i915-headers/gem/i915_gem_object.h b/drivers/gpu/drm/xe/compat-i915-headers/gem/i915_gem_object.h
> index 5f19550cc845..6739dadaf1a9 100644
> --- a/drivers/gpu/drm/xe/compat-i915-headers/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/xe/compat-i915-headers/gem/i915_gem_object.h
> @@ -7,6 +7,7 @@
>  #define _I915_GEM_OBJECT_H_
>  
>  #include <linux/types.h>
> +#include <linux/iosys-map.h>
>  
>  #include "xe_bo.h"
>  
> @@ -36,6 +37,7 @@ static inline int i915_gem_object_read_from_page(struct xe_bo *bo,
>  {
>  	struct ttm_bo_kmap_obj map;
>  	void *virtual;
> +	struct iosys_map vaddr;
>  	bool is_iomem;
>  	int ret;
>  
> @@ -52,10 +54,11 @@ static inline int i915_gem_object_read_from_page(struct xe_bo *bo,
>  	ofs &= ~PAGE_MASK;
>  	virtual = ttm_kmap_obj_virtual(&map, &is_iomem);
>  	if (is_iomem)
> -		*ptr = readq((void __iomem *)(virtual + ofs));
> +		iosys_map_set_vaddr_iomem(&vaddr, (void __iomem *)(virtual));

Should we just use a memcpy_fromio (and memcpy in the else branch) and
pass the size actually requested rather than hardcoding it to a u64?  At
the moment the only callsite happens to want a u64, and thus the Xe
compat header has an XE_WARN_ON that complains if any other size is
requested, but in theory this function is supposed to be general purpose
and take any size.


Matt

>  	else
> -		*ptr = *(u64 *)(virtual + ofs);
> +		iosys_map_set_vaddr(&vaddr, virtual);
>  
> +	*ptr = iosys_map_rd(&vaddr, ofs, u64);
>  	ttm_bo_kunmap(&map);
>  out_unlock:
>  	xe_bo_unlock(bo);
> -- 
> 2.40.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation