Re: [PATCH] drivers/perf: riscv: Remove redundant macro check

From: Charlie Jenkins <charlie@rivosinc.com>
To: Conor Dooley <conor@kernel.org>
Cc: Xiao Wang <xiao.w.wang@intel.com>,
	Alexandre Ghiti <alexghiti@rivosinc.com>,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, atishp@atishpatra.org,
	anup@brainfault.org, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drivers/perf: riscv: Remove redundant macro check
Date: Tue, 9 Jul 2024 13:57:47 -0700	[thread overview]
Message-ID: <Zo2kSxsJkdkBdBEW@ghost> (raw)
In-Reply-To: <20240709-unengaged-handgrip-56a5c7b3e1d1@spud>

On Tue, Jul 09, 2024 at 09:44:17PM +0100, Conor Dooley wrote:
> On Tue, Jul 09, 2024 at 01:29:42PM -0700, Charlie Jenkins wrote:
> > On Mon, Jul 08, 2024 at 01:22:11PM +0100, Conor Dooley wrote:
> > > On Mon, Jul 08, 2024 at 08:12:24PM +0800, Xiao Wang wrote:
> > > > The macro CONFIG_RISCV_PMU must have been defined when riscv_pmu.c gets
> > > > compiled, so this patch removes the redundant check.
> > > 
> > > Did you investigate why this define was added? Why do you think that it
> > > is redundant, rather than checking the incorrect config option?
> > 
> > This file is only compiled with CONFIG_RISCV_PMU:
> 
> I might be ill, but I can still read. I was not disagreeing with Xiao
> that the condition is redundant as written - I want to know whether they
> made sure that this check was intentionally using CONFIG_RISCV_PMU in the
> first place, or if another option should have been here instead.

Makes sense! Looking through the lists I see this RFC from Atish where
he introduced a different config option for this
"CONFIG_RISCV_PMU_COMMON"[1]. I wonder if something got confused in the
development of these two patches.

Link:
https://lore.kernel.org/lkml/20240217005738.3744121-12-atishp@rivosinc.com/
[1]

- Charlie

> 
> > 
> > # drivers/perf/Makefile
> > obj-$(CONFIG_RISCV_PMU) += riscv_pmu.o
> > 
> > So having this check does seem redundant. I am copying Alex as it looks
> > like he wrote this.
> > 
> > - Charlie
> > 
> > > 
> > > Cheers,
> > > Conor.
> > > 
> > > > 
> > > > Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> > > > ---
> > > >  drivers/perf/riscv_pmu.c | 2 --
> > > >  1 file changed, 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c
> > > > index 0a02e85a8951..7644147d50b4 100644
> > > > --- a/drivers/perf/riscv_pmu.c
> > > > +++ b/drivers/perf/riscv_pmu.c
> > > > @@ -39,7 +39,6 @@ void arch_perf_update_userpage(struct perf_event *event,
> > > >  	userpg->cap_user_time_short = 0;
> > > >  	userpg->cap_user_rdpmc = riscv_perf_user_access(event);
> > > >  
> > > > -#ifdef CONFIG_RISCV_PMU
> > > >  	/*
> > > >  	 * The counters are 64-bit but the priv spec doesn't mandate all the
> > > >  	 * bits to be implemented: that's why, counter width can vary based on
> > > > @@ -47,7 +46,6 @@ void arch_perf_update_userpage(struct perf_event *event,
> > > >  	 */
> > > >  	if (userpg->cap_user_rdpmc)
> > > >  		userpg->pmc_width = to_riscv_pmu(event->pmu)->ctr_get_width(event->hw.idx) + 1;
> > > > -#endif
> > > >  
> > > >  	do {
> > > >  		rd = sched_clock_read_begin(&seq);
> > > > -- 
> > > > 2.25.1
> > > > 
> > > > 
> > > > _______________________________________________
> > > > linux-riscv mailing list
> > > > linux-riscv@lists.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> > 