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Mon, 10 May 2021 20:59:27 -0700 (PDT) Subject: Re: [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend To: Robin Gong , wim@linux-watchdog.org, shawnguo@kernel.org, s.hauer@pengutronix.de, festevam@gmail.com Cc: linux-imx@nxp.com, kernel@pengutronix.de, linux-watchdog@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <1620732032-7675-1-git-send-email-yibin.gong@nxp.com> From: Guenter Roeck Message-ID: Date: Mon, 10 May 2021 20:59:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <1620732032-7675-1-git-send-email-yibin.gong@nxp.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210510_205929_307486_03C2DE39 X-CRM114-Status: GOOD ( 24.02 ) /bin/ln: failed to access 'reaver_cache/texts/20210510_205929_307486_03C2DE39': No such file or directory X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210510_205929_307486_03C2DE39 X-CRM114-Status: GOOD ( 20.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/11/21 4:20 AM, Robin Gong wrote: > Since watchdog_ping_work is not freezable so that it maybe scheduled before > imx2_wdt_resume where watchdog clock enabled, hence, kernel will hang in > imx2_wdt_ping without clock, and then watchdog reset happen. Prevent the > above case by clearing WDOG_HW_RUNNING before suspend, and restore it with > ping in imx2_wdt_resume. > > Signed-off-by: Robin Gong > --- > drivers/watchdog/imx2_wdt.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c > index b84f80f..d3751e9 100644 > --- a/drivers/watchdog/imx2_wdt.c > +++ b/drivers/watchdog/imx2_wdt.c > @@ -357,6 +357,13 @@ static int __maybe_unused imx2_wdt_suspend(struct device *dev) > */ > __imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME); > imx2_wdt_ping(wdog); > + > + /* > + * clear WDOG_HW_RUNNING to prevent watchdog_ping_work running > + * before imx2_wdt_resume where clock enabled, otherwise kernel > + * will hang and watchdog reset happen then. > + */ > + clear_bit(WDOG_HW_RUNNING, &wdog->status); > } > > clk_disable_unprepare(wdev->clk); > @@ -386,6 +393,7 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev) > if (imx2_wdt_is_running(wdev)) { > imx2_wdt_set_timeout(wdog, wdog->timeout); > imx2_wdt_ping(wdog); > + set_bit(WDOG_HW_RUNNING, &wdog->status); > } > > return 0; > I really don't like this; it depends on assumptions how the watchdog core works, and it misuses WDOG_HW_RUNNING to indicate that the clock is stopped (or that the driver is in suspend mode). If ping doesn't work with the clock stopped, I think it would be much better to have a flag indicating that the clock is stopped, and have the ping function do nothing if it is called with stopped clock (ie if suspended). Guenter _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel