[Intel-gfx] [PATCH v2] drm/i915: use unsigned long for platform_mask

[Tvrtko Ursulin]

On 03/04/2019 02:46, Lucas De Marchi wrote:
> No reason to stick to u32 for platform mask if we can just use more bits
> on 64 bit platforms.
> 
> $ size drivers/gpu/drm/i915/i915.ko*
>     text	   data	    bss	    dec	    hex	filename
> 1884779	  41334	   5408	1931521	 1d7901	drivers/gpu/drm/i915/i915.ko
> 1886693	  41358	   5408	1933459	 1d8093	drivers/gpu/drm/i915/i915.ko.old

How did you get such a large difference, and decrease even? Could you 
check in the code what is happening? Because I get an increase with this 
patch:

    text    data     bss     dec     hex filename
1905314   43903    7424 1956641  1ddb21 i915.ko.orig
1905796   43903    7424 1957123  1ddd03 i915.ko.patch

Regards,

Tvrtko

> 
> Now on 64 bits we have only one long as opposed to 2 u32:
> 
> $ pahole -C intel_runtime_info drivers/gpu/drm/i915/i915.ko
> struct intel_runtime_info {
> 	long unsigned int          platform_mask[1];     /*     0     8 */
> ...
> }
> 
> On 32 bits we still have the same thing as before:
> $ size drivers/gpu/drm/i915/i915.ko*
>     text	   data	    bss	    dec	    hex	filename
> 1489839	  32485	   2816	1525140	 174594	drivers/gpu/drm/i915/i915.ko
> 1489839	  32485	   2816	1525140	 174594	drivers/gpu/drm/i915/i915.ko.old
> 
> Besides reducing the code on x86-64 now the array size is automatically
> calculated and we don't have to worry about extending it anymore.
> 
> v2: fix sparse and checkpatch warnings
> 
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h          | 6 +-----
>   drivers/gpu/drm/i915/intel_device_info.h | 7 +++----
>   2 files changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 0ab4826921f7..9fe765ffe878 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2309,10 +2309,6 @@ __platform_mask_index(const struct intel_runtime_info *info,
>   	const unsigned int pbits =
>   		BITS_PER_TYPE(info->platform_mask[0]) - INTEL_SUBPLATFORM_BITS;
>   
> -	/* Expand the platform_mask array if this fails. */
> -	BUILD_BUG_ON(INTEL_MAX_PLATFORMS >
> -		     pbits * ARRAY_SIZE(info->platform_mask));
> -
>   	return p / pbits;
>   }
>   
> @@ -2354,7 +2350,7 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
>   	const unsigned int pi = __platform_mask_index(info, p);
>   	const unsigned int pb = __platform_mask_bit(info, p);
>   	const unsigned int msb = BITS_PER_TYPE(info->platform_mask[0]) - 1;
> -	const u32 mask = info->platform_mask[pi];
> +	const unsigned long mask = info->platform_mask[pi];
>   
>   	BUILD_BUG_ON(!__builtin_constant_p(p));
>   	BUILD_BUG_ON(!__builtin_constant_p(s));
> diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
> index 0e579f158016..2f5ca2b6f094 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.h
> +++ b/drivers/gpu/drm/i915/intel_device_info.h
> @@ -214,11 +214,10 @@ struct intel_runtime_info {
>   	 * Platform mask is used for optimizing or-ed IS_PLATFORM calls into
>   	 * into single runtime conditionals, and also to provide groundwork
>   	 * for future per platform, or per SKU build optimizations.
> -	 *
> -	 * Array can be extended when necessary if the corresponding
> -	 * BUILD_BUG_ON is hit.
>   	 */
> -	u32 platform_mask[2];
> +	unsigned long platform_mask[DIV_ROUND_UP(INTEL_MAX_PLATFORMS,
> +						 BITS_PER_TYPE(unsigned long)
> +						 - INTEL_SUBPLATFORM_BITS)];
>   
>   	u16 device_id;
>   
>