Re: [PATCH 1/3] drm/i915: Make IS_GENx macros work on a mask

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/3] drm/i915: Make IS_GENx macros work on a mask
Date: Fri, 6 May 2016 15:28:44 +0100	[thread overview]
Message-ID: <20160506142844.GE30822@nuc-i3427.alporthouse.com> (raw)
In-Reply-To: <1462542231-7321-1-git-send-email-tvrtko.ursulin@linux.intel.com>

On Fri, May 06, 2016 at 02:43:49PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> If instead of numerical comparison me make these test a
> bitmask, we enable the compiler to optimize all instances
> of IS_GENx || IS_GENy.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_dma.c |  3 +++
>  drivers/gpu/drm/i915/i915_drv.h | 17 +++++++++--------
>  2 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index ad7abe517700..01163da51b1d 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1071,6 +1071,9 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv,
>  	memcpy(device_info, info, sizeof(dev_priv->info));
>  	device_info->device_id = dev->pdev->device;
>  
> +	BUG_ON(device_info->gen > sizeof(device_info->gen_mask) * 8);

Should be gen >= num_bits
BITS_PER_BYTE

> +	device_info->gen_mask = 1 << device_info->gen;

device_info->gen_mask = BIT(device_info->gen) for consistency;
> +
>  	spin_lock_init(&dev_priv->irq_lock);
>  	spin_lock_init(&dev_priv->gpu_error.lock);
>  	mutex_init(&dev_priv->backlight_lock);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d5496aba1cd5..c6351016eaf0 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -760,6 +760,7 @@ struct intel_device_info {
>  	u8 num_pipes:3;
>  	u8 num_sprites[I915_MAX_PIPES];
>  	u8 gen;
> +	u16 gen_mask;

Holey? Move gen_mask next to device id, and those u8
num_pipes/num_sprites can be moved down to the array of u8s.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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