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From: Jean Delvare <jdelvare@suse.de>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>,
	linux-acpi@vger.kernel.org,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Guenter Roeck <linux@roeck-us.net>,
	linux-watchdog@vger.kernel.org,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Tom Abraham <tabraham@suse.com>
Subject: wdat_wdt: access width inconsistency
Date: Mon, 10 Feb 2020 11:16:38 +0100
Message-ID: <20200210111638.64925c8e@endymion> (raw)

Hi all,

I'm still working on my customer issue where the wdat_wdt driver
reboots the server instantly as soon as the watchdog daemon is started.
I looked at all the upstream fixes and we already have all relevant
ones in our kernel so I start suspecting either a driver bug or a BIOS
issue.

While reading the driver code I noticed one suspect thing related to
the register access width, which I'd like a second opinion on.

Both acpi_watchdog.c and wdat_wdt.c contain code like:

	res.end = res.start + gas->access_width - 1;

This suggests that gas->access_width is expected to be 4 in case of a
32-bit register. However in wdat_wdt_read/wdat_wdt_write we have:

	switch (gas->access_width) {
	(...)
	case 3:
		*value = ioread32(instr->reg);

This looks inconsistent to me.

My reading of the ACPI specification suggests that 3 is the right value
for 32-bit registers. If so, then shouldn't the resource's end be set
to:

	res.end = res.start + (1 << (gas->access_width - 1)) - 1;

?

Thanks,
-- 
Jean Delvare
SUSE L3 Support

             reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10 10:16 Jean Delvare [this message]
2020-02-10 11:23 ` Mika Westerberg
2020-02-11 13:11   ` Jean Delvare
2020-02-11 13:59     ` Mika Westerberg
2020-02-11 16:25       ` Jean Delvare
2020-02-11 16:37         ` Mika Westerberg
2020-02-11 17:03           ` Jean Delvare
2020-02-12 11:05             ` [PATCH 1/3] ACPICA: Introduce ACPI_ACCESS_BIT_WIDTH() macro Mika Westerberg
2020-02-12 11:05               ` [PATCH 2/3] ACPI / watchdog: Fix gas->access_width usage Mika Westerberg
2020-02-12 11:56                 ` Jean Delvare
2020-02-12 12:10                   ` Mika Westerberg
2020-02-12 11:05               ` [PATCH 3/3] ACPI / watchdog: Set default timeout in probe Mika Westerberg
2020-02-12 12:07                 ` Jean Delvare
2020-02-12 12:13                   ` Mika Westerberg
2020-02-12 11:52               ` [PATCH 1/3] ACPICA: Introduce ACPI_ACCESS_BIT_WIDTH() macro Jean Delvare
2020-02-12 12:08                 ` Mika Westerberg
2020-02-11 16:45         ` wdat_wdt: access width inconsistency Guenter Roeck
2020-02-12 10:30   ` Jean Delvare
2020-02-12 10:47     ` Mika Westerberg
2020-02-12 11:05       ` Jean Delvare

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