Re: [PATCH 12/20] drm/i915/icl: Check for fused-off VDBOX and VEBOX instances

From: Sagar Arun Kamble <sagar.a.kamble@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Mika Kuoppala <mika.kuoppala@linux.intel.com>,
	intel-gfx@lists.freedesktop.org
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: Re: [PATCH 12/20] drm/i915/icl: Check for fused-off VDBOX and VEBOX instances
Date: Sat, 17 Feb 2018 17:40:32 +0530	[thread overview]
Message-ID: <f43a0040-6b2a-5818-6838-a502eafd7f27@intel.com> (raw)
In-Reply-To: <151885828715.7225.2871916243535188597@mail.alporthouse.com>


On 2/17/2018 2:34 PM, Chris Wilson wrote:
> Quoting Sagar Arun Kamble (2018-02-17 08:51:44)
>> Earlier I had thought of calling ASSIGN_FW_DOMAINS_TABLE,
>> ASSIGN_*_MMIO_VFUNCS before intel_uncore_fw_domains_init
>> and use I915_READ here for reading the fuse. But that approach seems to
>> expose the vfuncs and forcewake table before fw domains
>> are initialized. Although we can get to know invalid access to
>> read/write accessors before fw_domains get initialized, current ordering
>> of fw_domains init followed by fw domain table/read/write vfuncs init
>> seems right. So using fw_domains_get/put as suggested above
>> should be the way.
>>
>> Chris, Tvrtko, Mika, do you agree?
> What's the complication with the fw_domains? Do the additional powerwell
> depend on the fused status of the extra engines? Does it matter if the
> fw_domain are prepped if they are never used?
Yes. To discover the available VD/VE engines/power domains, fuse needs 
to be read under blitter forcewake as
RC6 will be enabled by BIOS. We do have usage of forcewake in IVB to 
discover FORCEWAKE_MT availability in fw_domains_init.
It should not be a problem if they are prepped but never used.
> Imo, I would have placed the fused discovery in
> intel_engines_init_mmio() (where we do the setup and can take forcewake).
> Then adding something like intel_uncore_reinit_mmio() (which would just
> prune the uncore->fw_domains) after checking fused status with commentary
> doesn't seem that horrible.
Yes. This approach looks good too. But, we might want to optimize the 
driver_load to avoid this setup at first place
instead of pruning later.
Another related setup that can be avoided/pruned is the fw_range for the 
engine fused off as it can improve the fw lookup.
> -Chris

-- 
Thanks,
Sagar

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx