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From: "Heiko Stübner" <heiko@sntech.de>
To: Andreas Schwab <schwab@suse.de>
Cc: atishp@atishpatra.org, anup@brainfault.org, will@kernel.org,
	mark.rutland@arm.com, paul.walmsley@sifive.com,
	palmer@dabbelt.com, aou@eecs.berkeley.edu,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Conor.Dooley@microchip.com
Subject: Re: [PATCH v3] drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores
Date: Mon, 05 Sep 2022 20:59:53 +0200	[thread overview]
Message-ID: <8712127.JRmrKFJ9eK@diego> (raw)
In-Reply-To: <mvm4jxlao6f.fsf@suse.de>

Hi Andreas,

Am Montag, 5. September 2022, 16:30:48 CEST schrieb Andreas Schwab:
> On Sep 05 2022, Heiko Stuebner wrote:
> > To work properly, this requires a matching change in SBI, though the actual
> > interface between kernel and SBI does not change.
> 
> What happens if you mix different kernel and SBI versions?

The interface kernel <-> sbi itself is not changed at all and this of
course only matters to t-head c9xx cpu cores, so I guess we have
the cases:

- non-t-head core:
  no behaviour change independent of versions


- t-head core with everything "old":
  would just uses the regular sbi pmu setup, but as the necessary
  sbi-side pmu config for the c9xx isn't set from u-boot
  (dt-properties mapping sbi-events to the values needed to be written
   to mhpmevent*), this is broken anyway with standard sbi
  

- t-head core with "old" kernel, "new" sbi:
  kernel does not detect the extended features, so should fall back
  to just use the standard pmu features
  

- t-head core with "new" kernel", "old" sbi:
  Same as everything "old", pmu isn't setup correctly in sbi anyway
  for the c9xx at the moment


Heiko  



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WARNING: multiple messages have this Message-ID (diff)
From: "Heiko Stübner" <heiko@sntech.de>
To: Andreas Schwab <schwab@suse.de>
Cc: atishp@atishpatra.org, anup@brainfault.org, will@kernel.org,
	mark.rutland@arm.com, paul.walmsley@sifive.com,
	palmer@dabbelt.com, aou@eecs.berkeley.edu,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Conor.Dooley@microchip.com
Subject: Re: [PATCH v3] drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores
Date: Mon, 05 Sep 2022 20:59:53 +0200	[thread overview]
Message-ID: <8712127.JRmrKFJ9eK@diego> (raw)
In-Reply-To: <mvm4jxlao6f.fsf@suse.de>

Hi Andreas,

Am Montag, 5. September 2022, 16:30:48 CEST schrieb Andreas Schwab:
> On Sep 05 2022, Heiko Stuebner wrote:
> > To work properly, this requires a matching change in SBI, though the actual
> > interface between kernel and SBI does not change.
> 
> What happens if you mix different kernel and SBI versions?

The interface kernel <-> sbi itself is not changed at all and this of
course only matters to t-head c9xx cpu cores, so I guess we have
the cases:

- non-t-head core:
  no behaviour change independent of versions


- t-head core with everything "old":
  would just uses the regular sbi pmu setup, but as the necessary
  sbi-side pmu config for the c9xx isn't set from u-boot
  (dt-properties mapping sbi-events to the values needed to be written
   to mhpmevent*), this is broken anyway with standard sbi
  

- t-head core with "old" kernel, "new" sbi:
  kernel does not detect the extended features, so should fall back
  to just use the standard pmu features
  

- t-head core with "new" kernel", "old" sbi:
  Same as everything "old", pmu isn't setup correctly in sbi anyway
  for the c9xx at the moment


Heiko  



  reply	other threads:[~2022-09-05 19:44 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-05 14:16 [PATCH v3] drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores Heiko Stuebner
2022-09-05 14:16 ` Heiko Stuebner
2022-09-05 14:30 ` Andreas Schwab
2022-09-05 14:30   ` Andreas Schwab
2022-09-05 18:59   ` Heiko Stübner [this message]
2022-09-05 18:59     ` Heiko Stübner
2022-09-05 19:17 ` Conor.Dooley
2022-09-05 19:17   ` Conor.Dooley
2022-09-07 17:57 ` Heiko Stübner
2022-09-07 17:57   ` Heiko Stübner
     [not found] ` <CAOnJCU+SXQsho=t1vUQFiiDVU7-F0yaAH3ae4nUdYQWEyjmsjw@mail.gmail.com>
2022-09-07 23:15   ` Atish Patra
2022-09-07 23:15     ` Atish Patra

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