[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20200923043907.GA5146@codeaurora.org>
Date: Wed, 23 Sep 2020 12:39:07 +0800
From: Tingwei Zhang <tingweiz@...eaurora.org>
To: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Tingwei Zhang <tingwei@...eaurora.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexandre Torgue <alexandre.torgue@...com>,
tsoni@...eaurora.org,
Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
Mao Jinlong <jinlmao@...eaurora.org>,
linux-kernel@...r.kernel.org,
linux-stm32@...md-mailman.stormreply.com,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 6/6] stm class: ftrace: use different channel
accroding to CPU
On Fri, Sep 18, 2020 at 08:45:52PM +0800, Alexander Shishkin wrote:
> Tingwei Zhang <tingwei@...eaurora.org> writes:
>
> > @@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
> > {
> > int ret;
> >
> > + stm_ftrace.data.nr_chans = num_possible_cpus();
>
> Not a problem with this patch necesarily, but this made me realize that
> .nr_chans may be larger than:
>
> (1) what the policy permits,
> (2) what the stm device can handle.
>
> While (1) the user can fix in the policy, they won't be able to fix (2),
> in which case they won't be able to use stm_ftrace at all. I'm thinking
> if a link-time callback would be good enough.
>
Hi Alex,
I'm not sure if I understand this correct. If the nr_chans requested by
stm_ftrace is larger than policy permits or stm device can handle,
stm_assign_first_policy() returns with error so stm_source_link_add()
will fail. User would notice that when link happens. There's not much
we can do if resource is not enough.
> Another thing is that .nr_chans needs to be a power of 2 at the moment.
>
I'll change to below.
stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
> Regards,
> --
> Alex
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Powered by blists - more mailing lists