[Intel-gfx] [PATCH v2 (rebased) 4/4] drm/i915: Add locking to pll updates, v2.

Maarten Lankhorst maarten.lankhorst at linux.intel.com
Wed Mar 16 17:48:02 UTC 2016

Op 16-03-16 om 17:19 schreef Ander Conselvan De Oliveira:
> On Mon, 2016-03-14 at 09:27 +0100, Maarten Lankhorst wrote:
>> With async modesets this is no longer protected with connection_mutex,
>> so ensure that each pll has its own lock. The pll configuration state
>> is still protected; it's only the pll updates that need locking against
>> concurrency.
> I think I need to look at your async branch, since I'm not really sure how async
> will work. But locking the individual plls might fail in SKL with the current
> code. The register DPLL_CTRL1 controls all 4 plls, and currently it is updated
> with a read-modify-write in the enable hook, so we can't update two plls
> concurrently.
Would making the dpll lock global help? I don't think in practice the locks will be contended much,
it's not a performance sensitive path.


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