linux-kernel - Re: [PATCH] OPP: debugfs: Use performance level to distinguish between rates

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Message-ID: <nbm2hpbh5ejpyig344tlfod7armbavv33u7mwo7ur3nhaarnvl@jkelr2ni4vpy>
Date: Fri, 30 Jan 2026 12:47:36 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: vireshk@...nel.org, nm@...com, sboyd@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH] OPP: debugfs: Use performance level to distinguish
 between rates

On Fri, Jan 30, 2026 at 12:01:37PM +0530, Viresh Kumar wrote:
> On 29-01-26, 23:03, Manivannan Sadhasivam wrote:
> > Some OPP tables have entries with same rate and different performance
> > level. For these entries, using only the rate as the debugfs directory name
> > causes below error:
> > 
> > debugfs: 'opp:5000000' already exists in 'soc@...c00000.pci'
> > 
> > Fix it by appending the performance level to the dir name.
> > 
> > Reported-by: Bjorn Andersson <andersson@...nel.org>
> > Closes: https://lore.kernel.org/linux-arm-msm/75lzykd37zdvrks5i2bb4zb2yzjtm25kv3hegmikndkbr772mz@w2ykff3ny45u/
> > Fixes: 05db35963eef ("OPP: Add support to find OPP for a set of keys")
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > ---
> >  drivers/opp/debugfs.c | 13 ++++++++-----
> >  1 file changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
> > index 8fc6238b1728..7c912bae2a5a 100644
> > --- a/drivers/opp/debugfs.c
> > +++ b/drivers/opp/debugfs.c
> > @@ -131,21 +131,24 @@ void opp_debug_create_one(struct dev_pm_opp *opp, struct opp_table *opp_table)
> >  	struct dentry *pdentry = opp_table->dentry;
> >  	struct dentry *d;
> >  	unsigned long id;
> > -	char name[25];	/* 20 chars for 64 bit value + 5 (opp:\0) */
> > +	char name[36];	/* "opp:"(4) + u64(20) + "-" (1) + u32(10) + NULL(1) */
> >  
> >  	/*
> >  	 * Get directory name for OPP.
> >  	 *
> > -	 * - Normally rate is unique to each OPP, use it to get unique opp-name.
> > +	 * - Normally rate is unique to each OPP, use it to get unique opp-name,
> > +	 *   together with performance level.
> >  	 * - For some devices rate isn't available or there are multiple, use
> >  	 *   index instead for them.
> >  	 */
> > -	if (likely(opp_table->clk_count == 1 && opp->rates[0]))
> > +	if (likely(opp_table->clk_count == 1 && opp->rates[0])) {
> >  		id = opp->rates[0];
> > -	else
> > +		snprintf(name, sizeof(name), "opp:%lu-%u", id, opp->level);
> 
> This would be confusing for devices that don't have the level
> property. Maybe add the second part only if level is used.
> 

Yeah. I got to know that the level field as an 'OPP_LEVEL_UNSET' default value.
So I can use that:

+       if (likely(opp_table->clk_count == 1 && opp->rates[0])) {
+               if (opp->level == OPP_LEVEL_UNSET)
+                       snprintf(name, sizeof(name), "opp:%lu", opp->rates[0]);
+               else
+                       snprintf(name, sizeof(name), "opp:%lu-%u", opp->rates[0], opp->level);
+       } else {
+               snprintf(name, sizeof(name), "opp:%u", _get_opp_count(opp_table));
+       }

- Mani

-- 
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