[Intel-gfx] [PATCH 4/4] drm/i915: Use the real cpu max frequency for ring scaling

Daniel Vetter daniel at ffwll.ch
Tue Oct 8 08:14:03 CEST 2013

On Mon, Oct 07, 2013 at 05:15:48PM -0300, Rodrigo Vivi wrote:
> From: Ben Widawsky <benjamin.widawsky at intel.com>
> The policy's max frequency is not equal to the CPU's max frequency. The
> ring frequency is derived from the CPU frequency, and not the policy
> frequency.
> One example of how this may differ through sysfs. If the sysfs max
> frequency is modified, that will be used for the max ring frequency
> calculation.
> (/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq). As far as I
> know, no current governor uses anything but max as the default, but in
> theory, they could. Similarly distributions might set policy as part of
> their init process.
> It's ideal to use the real frequency because when we're currently scaled
> up on the GPU. In this case we likely want to race to idle, and using a
> less than max ring frequency is non-optimal for this situation.
> AFAIK, this patch should have no impact on a majority of people.
> This behavior hasn't been changed since it was first introduced:
> commit 23b2f8bb92feb83127679c53633def32d3108e70
> Author: Jesse Barnes <jbarnes at virtuousgeek.org>
> Date:   Tue Jun 28 13:04:16 2011 -0700
>     drm/i915: load a ring frequency scaling table v3
> CC: Jesse Barnes <jbarnes at virtuousgeek.org>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>

Queued for -next, thanks for the patch.
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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