linux-kernel - Re: [PATCH V2] spmi: pmic-arb: Enforce the ownership check optionally

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Message-ID: <20170830210203.GS21656@codeaurora.org>
Date:   Wed, 30 Aug 2017 14:02:03 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Shawn Guo <shawnguo@...nel.org>
Cc:     Kiran Gunda <kgunda@...eaurora.org>, gregkh@...uxfoundation.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
        David Collins <collinsd@...eaurora.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH V2] spmi: pmic-arb: Enforce the ownership check optionally

On 08/26, Shawn Guo wrote:
> On Fri, Aug 25, 2017 at 04:18:18PM -0700, Stephen Boyd wrote:
> > 
> > Right. Does the GPIO work? If so, it sounds like the read/write
> > access checks in spmi pmic arb don't work properly.
> 
> The check works.  With the check in there, PM8916 GPIO doesn't work.
> However, the consequence is that not only user3 but all GPIO leds under
> 'leds' node will fail to register, because any GPIO led's failing on
> create_gpio_led() makes leds-gpio driver probe fail as a while.  That's
> how leds-gpio driver works.
> 
> Also, per schematics, PM8916 GPIO1 is indeed routed to user3 LED on
> db410c board.  Why do you think apq8016-sbc device tree shouldn't use
> the GPIO for that at all?  Isn't it firmware's fault that the ownership
> of the peripheral is not properly configured?

If the ownership was not properly configured in the firmware,
then I imagine it would mean that we can't control the GPIO for
the LED. But that doesn't seem to be true. I can see on my board
that I get impermissible write failures on the GPIO when
controlling the GPIO brightness, but it doesn't actually matter
because the led still lights up. So the checks for write/read
permission seem incorrect, or they're not being enforced.

Anyway, I just wanted to make sure the GPIO still works, and it
looks like it does, so removing the permission checks is enough
to make me happy.

-- 
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