linux-kernel - Re: [PATCH 02/11] nvmem: qfprom: Mark core clk as optional

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Message-ID: <CAD=FV=WS2hgY=bQjLOs3Fdp8pbZyMsaS-0BpoxPq90Etfi+Xuw@mail.gmail.com>
Date:   Wed, 30 Aug 2023 07:30:41 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Luca Weiss <luca.weiss@...rphone.com>
Cc:     cros-qcom-dts-watchers@...omium.org,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH 02/11] nvmem: qfprom: Mark core clk as optional

Hi,

On Wed, Aug 30, 2023 at 2:58 AM Luca Weiss <luca.weiss@...rphone.com> wrote:
>
> On some platforms like sc7280 on non-ChromeOS devices the core clock
> cannot be touched by Linux so we cannot provide it. Mark it as optional
> as accessing qfprom works without it.
>
> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> ---
>  drivers/nvmem/qfprom.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Are you actually testing burning fuses from the OS, or are you just
using the nvmem in "read-only" mode? From comments in the bindings, if
you're trying to burn the fuses then the clock is required. If things
are in read-only mode then the clock isn't required.

When I compare to the driver, it seems like the driver assumes that if
more than one memory region is provided then you must be supporting
burning fuses. The bindings agree that having 4 memory regions
specified means that the nvmem supports burning and 1 memory region
specified means read-only. The extra 3 memory regions in the nvmem are
all about fuse burning, I believe.

So maybe the right fix here is to just change your dts to specify one
memory region?

-Doug