linux-kernel - Re: [PATCH] interconnect: Restore sync state by ignoring ipa-virt in provider count

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Date:   Tue, 3 May 2022 15:07:07 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Georgi Djakov <djakov@...nel.org>, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Doug Anderson <dianders@...omium.org>,
        Alex Elder <elder@...aro.org>,
        Taniya Das <quic_tdas@...cinc.com>,
        Mike Tipton <quic_mdtipton@...cinc.com>
Subject: Re: [PATCH] interconnect: Restore sync state by ignoring ipa-virt in
 provider count

Quoting Nathan Chancellor (2022-05-02 08:18:24)
> Hi Stephen,
>
> On Tue, Apr 26, 2022 at 06:32:26PM -0700, Stephen Boyd wrote:
> > Ignore compatible strings for the IPA virt drivers that were removed in
> > commits 2fb251c26560 ("interconnect: qcom: sdx55: Drop IP0
> > interconnects") and 2f3724930eb4 ("interconnect: qcom: sc7180: Drop IP0
> > interconnects") so that the sync state logic can kick in again.
> > Otherwise all the interconnects in the system will stay pegged at max
> > speeds because 'providers_count' is always going to be one larger than
> > the number of drivers that will ever probe on sc7180 or sdx55. This
> > fixes suspend on sc7180 and sdx55 devices when you don't have a
> > devicetree patch to remove the ipa-virt compatible node.
> >
> > Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> > Cc: Doug Anderson <dianders@...omium.org>
> > Cc: Alex Elder <elder@...aro.org>
> > Cc: Taniya Das <quic_tdas@...cinc.com>
> > Cc: Mike Tipton <quic_mdtipton@...cinc.com>
> > Fixes: 2fb251c26560 ("interconnect: qcom: sdx55: Drop IP0 interconnects")
> > Fixes: 2f3724930eb4 ("interconnect: qcom: sc7180: Drop IP0 interconnects")
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
>
> This patch as commit ad3cc2f05fda ("interconnect: Restore sync state by
> ignoring ipa-virt in provider count") in -next causes the following
> build warning when CONFIG_OF is disabled because of_match_node is just
> NULL:
>
> drivers/interconnect/core.c:1090:28: warning: unused variable 'ignore_list' [-Wunused-variable]
>         const struct of_device_id ignore_list[] = {
>                                   ^
> 1 warning generated.
>
> Should it just be marked as __maybe_unused or is there a different fix
> that would be more appropriate?

Yeah I think __maybe_unused would work. The other approach would be to
make of_match_node() a static inline that returns false with CONFIG_OF=n
but that's probably a super large change. I hope the compiler would be
able to optimize that whole thing away because the arguments are const
pointers but I don't know.