From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org,
Xingyu Wu <xingyu.wu@starfivetech.com>,
Ziv Xu <ziv.xu@starfivetech.com>
Subject: Re: [PATCH v2 6/8] watchdog: starfive-wdt: Avoid unclocked MMIO read in starfive_wdt_get_timeleft()
Date: Fri, 6 Nov 2026 14:22:01 +0000 [thread overview]
Message-ID: <au3iicqFfz6iuvF3@google.com> (raw)
In-Reply-To: <20261105190530.2371854-7-linux@roeck-us.net>
On Thu, Nov 05, 2026 at 11:05:27AM -0800, Guenter Roeck wrote:
> When the watchdog is inactive, runtime PM suspends the device and gates
> off apb_clk and core_clk via starfive_wdt_runtime_suspend(). However,
> reading the sysfs timeleft attribute via timeleft_show() or issuing
> ioctl(WDIOC_GETTIMELEFT) calls starfive_wdt_get_timeleft() unconditionally.
>
> Because starfive_wdt_get_timeleft() reads the counter and interrupt status
> registers without checking whether the hardware watchdog is running,
> querying timeleft while inactive performs unclocked MMIO reads and triggers
> a bus fault.
>
> Return 0 immediately in starfive_wdt_get_timeleft() when
> watchdog_hw_running() is false. When watchdog_hw_running() is true, the
> driver holds an active runtime PM reference keeping the clocks enabled.
>
> Fixes: db728ea9c7be ("drivers: watchdog: Add StarFive Watchdog driver")
> Cc: Xingyu Wu <xingyu.wu@starfivetech.com>
> Cc: Ziv Xu <ziv.xu@starfivetech.com>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
next prev parent reply other threads:[~2026-11-06 14:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 19:05 [PATCH v2 0/8] watchdog: starfive-wdt: Fix runtime PM and unclocked register access bugs Guenter Roeck
2026-11-05 19:05 ` [PATCH v2 1/8] watchdog: starfive-wdt: Drop runtime PM reference if starting watchdog fails Guenter Roeck
2026-11-05 19:05 ` [PATCH v2 2/8] watchdog: starfive-wdt: Balance pm_runtime_enable() on probe error paths Guenter Roeck
2026-11-05 19:05 ` [PATCH v2 3/8] watchdog: starfive-wdt: Avoid unclocked register access in remove and PM paths Guenter Roeck
2026-11-06 14:21 ` Tzung-Bi Shih
2026-11-05 19:05 ` [PATCH v2 4/8] watchdog: starfive-wdt: Fix runtime PM usage count leaks in probe and remove Guenter Roeck
2026-11-05 19:05 ` [PATCH v2 5/8] watchdog: starfive-wdt: Drop runtime PM reference before registering watchdog Guenter Roeck
2026-11-05 19:05 ` [PATCH v2 6/8] watchdog: starfive-wdt: Avoid unclocked MMIO read in starfive_wdt_get_timeleft() Guenter Roeck
2026-11-06 14:22 ` Tzung-Bi Shih [this message]
2026-11-05 19:05 ` [PATCH v2 7/8] watchdog: starfive-wdt: Stop ping worker on system suspend Guenter Roeck
2026-11-06 14:22 ` Tzung-Bi Shih
2026-11-05 19:05 ` [PATCH v2 8/8] watchdog: starfive-wdt: Avoid unclocked MMIO access in starfive_wdt_set_timeout() Guenter Roeck
2026-11-06 14:21 ` Tzung-Bi Shih
2026-11-06 15:20 ` Guenter Roeck
2026-11-06 15:51 ` Tzung-Bi Shih
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