linux-kernel - Re: [PATCH V2 2/2] firmware: arm_scmi: Skip adding bad duplicates

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Message-ID: <ZwaRMWG7iCEjp1Q3@pluto>
Date: Wed, 9 Oct 2024 15:20:33 +0100
From: Cristian Marussi <cristian.marussi@....com>
To: Sibi Sankar <quic_sibis@...cinc.com>
Cc: Cristian Marussi <cristian.marussi@....com>, sudeep.holla@....com,
	linux-kernel@...r.kernel.org, arm-scmi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
	johan@...nel.org, konradybcio@...nel.org
Subject: Re: [PATCH V2 2/2] firmware: arm_scmi: Skip adding bad duplicates

On Mon, Oct 07, 2024 at 12:30:14PM +0530, Sibi Sankar wrote:
> 
> 
> On 9/4/24 21:00, Cristian Marussi wrote:
> > On Wed, Sep 04, 2024 at 04:21:49PM +0100, Cristian Marussi wrote:
> > > On Wed, Sep 04, 2024 at 08:43:24AM +0530, Sibi Sankar wrote:
> > > > Ensure that the bad duplicates reported by the platform firmware doesn't
> > > > get added to the opp-tables.
> > > > 
> > > 
> > > Hi Sibi,
> > > 
> > > so if the idea is to make the code more robust when FW sends BAD
> > > duplicates, you necessarily need to properly drop opps in opp_count too.
> > > 
> > > One other option would be to just loop with xa_for_each BUT opp_count is
> > > used in a number of places...so first of all let's try drop count properly.
> > > 
> > > Can you try this patch down below, instead of your patch.
> > > If it solves, I will send a patch (after testing it a bit more :D)
> > 
> > Hold on... I sent you a diff that does not apply probably on your tree due
> > to some uncomitted local work of mine...my bad...let me resend.
> 
> Hey Cristian,
> Thanks for taking time to send out the diff. I thought this would be
> enough but there will still be a disconnect between opp_count and idx
> of the opp we populate. Consider a case were we get to have a valid
> opp just after duplicate opp. The opp_count will still limit us on what
> levels we are allowed to see.
>

Ah right...indeed... I missed that the opp_count is used also to loop on the
opps arrays and OPPs are not only accessed by xa_load....

...anyway the index in the dom->opp arrauy is NOT related to index/level
indexing, so we just have to have the bad oop dupicates also in the
array and NOT only in the XArray...

I am sending you, as a reply to this patch, a new version of my fix
with just a one-line difference tthat should solve completely the issue
also in the usecase that you describe.

Thanks,
Cristian