linux-kernel - Re: [RFC 18/18] power: supply: max17040: Do not enforce (incorrect) interrupt trigger type

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Date:   Fri, 11 Dec 2020 17:44:26 +0200
From:   Iskren Chernev <iskren.chernev@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-rtc@...r.kernel.org
Cc:     Matheus Castello <matheus@...tello.eng.br>,
        Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>,
        Angus Ainslie <angus@...ea.ca>,
        Hans de Goede <hdegoede@...hat.com>
Subject: Re: [RFC 18/18] power: supply: max17040: Do not enforce (incorrect)
 interrupt trigger type


On 12/11/20 9:47 AM, Krzysztof Kozlowski wrote:
 > On Thu, Dec 10, 2020 at 10:25:34PM +0100, Krzysztof Kozlowski wrote:
 >> Interrupt line can be configured on different hardware in different way,
 >> even inverted.  Therefore driver should not enforce specific trigger
 >> type - edge falling - but instead rely on Devicetree to configure it.
 >>
 >> The Maxim 14577/77836 datasheets describe the interrupt line as active
 >> low with a requirement of acknowledge from the CPU therefore the edge
 >> falling is not correct.
 >>
 >> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
 >>
 >> ---
 >>
 >> This patch should wait till DTS changes are merged, as it relies on
 >> proper Devicetree.
 >> ---
 >> .../devicetree/bindings/power/supply/max17040_battery.txt       | 2 +-
 >> drivers/power/supply/max17040_battery.c                         | 2 +-
 >>  2 files changed, 2 insertions(+), 2 deletions(-)
 >>
 >> diff --git 
a/Documentation/devicetree/bindings/power/supply/max17040_battery.txt 
b/Documentation/devicetree/bindings/power/supply/max17040_battery.txt
 >> index c802f664b508..194eb9fe574d 100644
 >> --- 
a/Documentation/devicetree/bindings/power/supply/max17040_battery.txt
 >> +++ 
b/Documentation/devicetree/bindings/power/supply/max17040_battery.txt
 >> @@ -39,7 +39,7 @@ Example:
 >>          reg = <0x36>;
 >>          maxim,alert-low-soc-level = <10>;
 >>          interrupt-parent = <&gpio7>;
 >> -        interrupts = <2 IRQ_TYPE_EDGE_FALLING>;
 >> +        interrupts = <2 IRQ_TYPE_LEVEL_LOW>;
 >>          wakeup-source;
 >>      };
 >>
 >> diff --git a/drivers/power/supply/max17040_battery.c 
b/drivers/power/supply/max17040_battery.c
 >> index d956c67d5155..f737de0470de 100644
 >> --- a/drivers/power/supply/max17040_battery.c
 >> +++ b/drivers/power/supply/max17040_battery.c
 >> @@ -367,7 +367,7 @@ static int max17040_enable_alert_irq(struct 
max17040_chip *chip)
 >>
 >>      flags = IRQF_TRIGGER_FALLING | IRQF_ONESHOT;
 >
 > This has to be removed. I will fix it in v2.
 >
 > Best regards,
 > Krzysztof

I removed the IRQF_TRIGGER_FALLING, tweaked the DT as per the DT patch, and
it worked on the samsung klte.

I don't understand how the DT irq flag ends up being used by the kernel. It
is never explicitly read from DT or passed to interrupt API, only i2c->irq,
which is a pure int.

Fixing the DT and the drivers will hopefully set a precedent, so future
drivers (when copied/tweaked from existing drivers) will do it right.

Acked-by: Iskren Chernev <iskren.chernev@...il.com>

 >>      ret = devm_request_threaded_irq(&client->dev, client->irq, NULL,
 >> -                    max17040_thread_handler, flags,
 >> +                    max17040_thread_handler, IRQF_ONESHOT,
 >>                      chip->battery->desc->name, chip);
 >>
 >>      return ret;
 >> --
 >> 2.25.1
 >>