linux-kernel - Re: [PATCH] watchdog: s3c2410_wdt: Report when the watchdog reset the system

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Message-ID: <CAD=FV=XqNnPVHSsKsU2_UrRoMVy8d+gh5eaZUy9xiEDaDBWO7w@mail.gmail.com>
Date:	Thu, 5 Dec 2013 10:16:07 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Leela Krishna Amudala <l.krishna@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Olof Johansson <olof@...om.net>,
	Wim Van Sebroeck <wim@...ana.be>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Ben Dooks <ben-linux@...ff.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] watchdog: s3c2410_wdt: Report when the watchdog reset the system

Tomasz

On Thu, Dec 5, 2013 at 8:18 AM, Tomasz Figa <t.figa@...sung.com> wrote:
> On Thursday 05 of December 2013 08:00:27 Guenter Roeck wrote:
>> On Thu, Dec 05, 2013 at 01:27:13PM +0530, Leela Krishna Amudala wrote:
>> > Hi Guenter Roeck,
>> >
>> > On Tue, Dec 3, 2013 at 3:06 AM, Guenter Roeck <linux@...ck-us.net> wrote:
>> > >
>> > > On Mon, Dec 02, 2013 at 12:47:53PM -0800, Olof Johansson wrote:
>> > > > On Mon, Dec 2, 2013 at 12:21 PM, Guenter Roeck <linux@...ck-us.net> wrote:
>> > > > > On Mon, Dec 02, 2013 at 10:14:41AM -0800, Doug Anderson wrote:
>> > > > >> A good watchdog driver is supposed to report when it was responsible
>> > > > >> for resetting the system.  Implement this for the s3c2410, at least on
>> > > > >> exynos5250 and exynos5420 where we already have a pointer to the PMU
>> > > > >> registers to read the information.
>> > > > >>
>> > > > >> Signed-off-by: Doug Anderson <dianders@...omium.org>
>> > > > >> ---
>> > > > >> This patch is based atop Leela Krishna's recent series that ends with
>> > > > >> (ARM: dts: update watchdog device nodes for Exynos5250 and Exynos5420)
>> > > > >> AKA <https://patchwork.kernel.org/patch/3251861/>.
>> > > > >>
>> > > > >>  drivers/watchdog/s3c2410_wdt.c | 42 +++++++++++++++++++++++++++++++++++++++---
>> > > > >>  1 file changed, 39 insertions(+), 3 deletions(-)
>> > > > >>
>> > > > >> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
>> > > > >> index 47f4dcf..2c87d37 100644
>> > > > >> --- a/drivers/watchdog/s3c2410_wdt.c
>> > > > >> +++ b/drivers/watchdog/s3c2410_wdt.c
>> > > > >> @@ -62,9 +62,13 @@
>> > > > >>  #define CONFIG_S3C2410_WATCHDOG_ATBOOT               (0)
>> > > > >>  #define CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME (15)
>> > > > >>
>> > > > >> +#define RST_STAT_REG_OFFSET          0x0404
>> > > > >>  #define WDT_DISABLE_REG_OFFSET               0x0408
>> > > > >>  #define WDT_MASK_RESET_REG_OFFSET    0x040c
>> > > > >>  #define QUIRK_NEEDS_PMU_CONFIG               (1 << 0)
>> > > > >> +#define QUIRK_HAS_RST_STAT           (1 << 1)
>> > > > >> +#define QUIRKS_NEED_PMUREG           (QUIRK_NEEDS_PMU_CONFIG | \
>> > > > >> +                                      QUIRK_HAS_RST_STAT)
>> > > > >>
>> > > > > I am not really happy about the NEED (both of them, really) here.
>> > > > > How about HAS instead ?
>> > > >
>> > > > Ah, I just commented on these things on our internal review site too
>> > > > on this patch. I don't even think a quirk is needed -- just use the
>> > > > presence of a non-0 rst_stat_reg to tell if you need to use regmap.
>> > > >
>> > > Agreed; same is true for the QUIRK_NEEDS_PMU_CONFIG related registers
>> > > as well.
>> > >
>> >
>> > As Tomasz Figa suggested I introduced quirks,
>> >
>> 'quirk' implies a workaround for non-standard or broken hardware,
>> not a flag indicating device specific functionality.
>
> I wouldn't limit meaning of "quirk" to only this. The word has been widely
> used around the kernel as a name for differences between hardware
> variants.
>
> As for the original issue itself, IMHO Doug's original solution is the
> most practical, as 0 can be a valid register offset and RST_STAT register
> could be used for other purposes as well in future, depending on other
> quirk flag.

OK, I'm keeping my concept but adjusting the names.  Version 2 coming
up shortly.

-Doug
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