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Message-ID: <d45ac9ca-2b65-3cff-989a-99db5a6096bb@linux.intel.com>
Date:   Tue, 2 Aug 2022 13:23:03 -0400
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Subject: Re: [PATCH V2 1/5] perf/x86/intel/uncore: Parse uncore discovery
 tables
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To:     Lucas De Marchi <lucas.demarchi@intel.com>
Cc:     peterz@infradead.org, mingo@kernel.org, acme@redhat.com,
        linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, eranian@google.com, namhyung@kernel.org,
        ak@linux.intel.com, tilak.tangudu@intel.com
References: <1616003977-90612-1-git-send-email-kan.liang@linux.intel.com>
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 <20220722125552.fmljascpvmi2b6ec@ldmartin-desk2>
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 <bec1bc73-b3bc-50da-8aa7-0aab2328d62f@linux.intel.com>
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 <20220802160237.uqgez4f3ctm7rpyc@ldmartin-desk2>
From:   "Liang, Kan" <kan.liang@linux.intel.com>
In-Reply-To: <20220802160237.uqgez4f3ctm7rpyc@ldmartin-desk2>
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On 2022-08-02 12:02 p.m., Lucas De Marchi wrote:
>>> 2) Trying to read the MMIOs when device is possibly in D3 state:
>>
>> The uncore driver skips the device which doesn't support the discovery
>> mechanism.
>> If 1) is fixed, the uncore driver will not touch the MMIO space of a PVC
>> device. The power issue should be gone.
>>
>> I've already sent you a patch to ignore the PVC added OOBMSM device, you
>> can double check with the patch.
> 
> (2) is a more generic issue that I'm mentioning. Forget for a moment we
> are talking about PVC - that will be fixed by (1). We are trying to read
> the mmio from a device that can be in D3, either because it started in
> D3 or because a driver, loaded before intel_uncore, moved it to that
> state. That won't work even if the device supports the discovery
> mechanism.

The uncore driver is designed to only support the *PMON* discovery
table, not all the discovery tables. The DEVSEC_ID 1 indicates the
*PMON* discovery table.

For other devices which support the discovery mechanism, they should use
another DEVSEC_ID. The uncore driver will ignore the device.

Thanks,
Kan