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SubjectRe: [PATCH] rtc: pcf2127: handle timestamp interrupts
Hello,

On 29/04/2021 16:47:58+0200, Mian Yousaf Kaukab wrote:
> commit 03623b4b041c ("rtc: pcf2127: add tamper detection support")
> added support for timestamp interrupts. However they are not being
> handled in the irq handler. If a timestamp interrupt occurs it
> results in kernel disabling the interrupt and displaying the call
> trace:
>
> [ 121.145580] irq 78: nobody cared (try booting with the "irqpoll" option)
> ...
> [ 121.238087] [<00000000c4d69393>] irq_default_primary_handler threaded [<000000000a90d25b>] pcf2127_rtc_irq [rtc_pcf2127]
> [ 121.248971] Disabling IRQ #78
>
> Handle timestamp interrupts in pcf2127_rtc_irq(). Display a message
> in kernel log when a timestamp interrupt occurs. Don’t check for
> TSF1 and TSF2 flags in timestamp0_show() as they are cleared in the
> IRQ handler now.

This breaks an important functionality (as I already replied to a
previous fix a while ago) as then there is no way to know whether the
timestamp is bogus or if an event really happened. Please fix properly.

>
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> ---
> drivers/rtc/rtc-pcf2127.c | 34 +++++++++++++++++++++++++---------
> 1 file changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> index d13c20a2adf7..0dbc0473cc68 100644
> --- a/drivers/rtc/rtc-pcf2127.c
> +++ b/drivers/rtc/rtc-pcf2127.c
> @@ -94,6 +94,13 @@
> #define PCF2127_WD_VAL_MAX 255
> #define PCF2127_WD_VAL_DEFAULT 60
>
> +/* Mask for currently enabled interrupts */
> +#define PCF2127_CTRL1_IRQ_MASK (PCF2127_BIT_CTRL1_TSF1)
> +#define PCF2127_CTRL2_IRQ_MASK ( \
> + PCF2127_BIT_CTRL2_AF | \
> + PCF2127_BIT_CTRL2_WDTF | \
> + PCF2127_BIT_CTRL2_TSF2)
> +
> struct pcf2127 {
> struct rtc_device *rtc;
> struct watchdog_device wdd;
> @@ -437,20 +444,33 @@ static int pcf2127_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> static irqreturn_t pcf2127_rtc_irq(int irq, void *dev)
> {
> struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
> - unsigned int ctrl2 = 0;
> + unsigned int ctrl1, ctrl2;
> int ret = 0;
>
> + ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL1, &ctrl1);
> + if (ret)
> + return IRQ_NONE;
> +
> ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL2, &ctrl2);
> if (ret)
> return IRQ_NONE;
>
> - if (!(ctrl2 & PCF2127_BIT_CTRL2_AF))
> + if (!(ctrl1 & PCF2127_CTRL1_IRQ_MASK || ctrl2 & PCF2127_CTRL2_IRQ_MASK))
> return IRQ_NONE;
>
> - regmap_write(pcf2127->regmap, PCF2127_REG_CTRL2,
> - ctrl2 & ~(PCF2127_BIT_CTRL2_AF | PCF2127_BIT_CTRL2_WDTF));
> + if (ctrl1 & PCF2127_CTRL1_IRQ_MASK)
> + regmap_write(pcf2127->regmap, PCF2127_REG_CTRL1,
> + ctrl1 & ~PCF2127_CTRL1_IRQ_MASK);
>
> - rtc_update_irq(pcf2127->rtc, 1, RTC_IRQF | RTC_AF);
> + if (ctrl2 & PCF2127_CTRL2_IRQ_MASK)
> + regmap_write(pcf2127->regmap, PCF2127_REG_CTRL2,
> + ctrl2 & ~PCF2127_CTRL2_IRQ_MASK);
> +
> + if (ctrl1 & PCF2127_BIT_CTRL1_TSF1 || ctrl2 & PCF2127_BIT_CTRL2_TSF2)
> + dev_info(dev, "timestamp interrupt generated");
> +

Please do not add random strings in the kernel, this will probably never
be seen by any real user.

> + if (ctrl2 & PCF2127_BIT_CTRL2_AF)
> + rtc_update_irq(pcf2127->rtc, 1, RTC_IRQF | RTC_AF);
>
> pcf2127_wdt_active_ping(&pcf2127->wdd);
>
> @@ -524,10 +544,6 @@ static ssize_t timestamp0_show(struct device *dev,
> if (ret)
> return ret;
>
> - if (!(data[PCF2127_REG_CTRL1] & PCF2127_BIT_CTRL1_TSF1) &&
> - !(data[PCF2127_REG_CTRL2] & PCF2127_BIT_CTRL2_TSF2))
> - return 0;
> -
> tm.tm_sec = bcd2bin(data[PCF2127_REG_TS_SC] & 0x7F);
> tm.tm_min = bcd2bin(data[PCF2127_REG_TS_MN] & 0x7F);
> tm.tm_hour = bcd2bin(data[PCF2127_REG_TS_HR] & 0x3F);
> --
> 2.26.2
>

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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