From: Sylvain Rochet <sylvain.rochet@finsecur.com>
To: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Peter Rosin <peda@axentia.se>,
Wenyou Yang <wenyou.yang@atmel.com>,
"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"alexandre.belloni@free-electrons.com"
<alexandre.belloni@free-electrons.com>
Subject: Re: [PATCH v2 02/12] pm: at91: Workaround DDRSDRC self-refresh bug with LPDDR1 memories.
Date: Mon, 26 Jan 2015 17:11:24 +0100 [thread overview]
Message-ID: <20150126161124.GA24190@gradator.net> (raw)
In-Reply-To: <54C66589.3040505@atmel.com>
Hello Nicolas and Peter,
On Mon, Jan 26, 2015 at 05:04:25PM +0100, Nicolas Ferre wrote:
> Le 26/01/2015 16:58, Peter Rosin a écrit :
> > Sylvain Rochet wrote:
> >> Hello Nicolas,
> >>
> >> On Mon, Jan 26, 2015 at 02:34:38PM +0100, Nicolas Ferre wrote:
> >>> Le 26/01/2015 11:36, Sylvain Rochet a écrit :
> >>>>
> >>>> I think we should explain we are dealing with an errata here, this
> >>>> is not obvious at first sight, the patch summary may find its place
> >>>> here :-)
> >>>
> >>> True but the problem is that this errata is not public yet, it will be
> >>> in a couple of weeks.
> >>>
> >>> I have the feeling though that the commit message is pretty clear.
> >>> We'll maybe add that it"s an actual errata.
> >>
> >> Humm, this is not what I meant actually. I only proposed a code source
> >> comment explaining why this is done this way, the current patch summary
> >> looked like it will be perfect between /* */ ;-)
> >
> > I did not want to fill up the source with wordy comments, and settled
> > for a one-liner. I don't know much about the underlying reasons other
> > than the fact that LPDDR1 mode of the controller isn't working properly
> > in self-refresh and that the DDR2 spec is similar enough to work.
> >
> > The one-liner comment says about the same thing, but not with so
> > many words. The comment does make it clear that the switch to DDR2
> > is intentional, and that is all that is needed as protection from some
> > future cleanup. I mean, anyone seeing that comment and just erasing
> > the whole thing without further investigation is not doing a very good
> > job as there is no reason to intentionally switch from LPDDR1 mode to
> > DDR2 mode, other that the fact that the LPDDR1 mode isn't working for
> > some reason. That reason is not to be found in the commit message
> > and I have no information to improve the situation. IMO, the only thing
> > missing is a pointer to the as yet unreleased errata, which should explain
> > the situation clearly for any and all interested parties. May I suggest that
> > someone who cares sends a patch with the comment update when the
> > errata is released?
>
> That's the option that I'll take.
>
> Let's go for it (and anyone remind me if I don't when the errata is
> released).
I fully agree with that, a pointer to a datasheet errata is exactly the
same thing as explaining the issue.
Sylvain
WARNING: multiple messages have this Message-ID (diff)
From: sylvain.rochet@finsecur.com (Sylvain Rochet)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 02/12] pm: at91: Workaround DDRSDRC self-refresh bug with LPDDR1 memories.
Date: Mon, 26 Jan 2015 17:11:24 +0100 [thread overview]
Message-ID: <20150126161124.GA24190@gradator.net> (raw)
In-Reply-To: <54C66589.3040505@atmel.com>
Hello Nicolas and Peter,
On Mon, Jan 26, 2015 at 05:04:25PM +0100, Nicolas Ferre wrote:
> Le 26/01/2015 16:58, Peter Rosin a ?crit :
> > Sylvain Rochet wrote:
> >> Hello Nicolas,
> >>
> >> On Mon, Jan 26, 2015 at 02:34:38PM +0100, Nicolas Ferre wrote:
> >>> Le 26/01/2015 11:36, Sylvain Rochet a ?crit :
> >>>>
> >>>> I think we should explain we are dealing with an errata here, this
> >>>> is not obvious at first sight, the patch summary may find its place
> >>>> here :-)
> >>>
> >>> True but the problem is that this errata is not public yet, it will be
> >>> in a couple of weeks.
> >>>
> >>> I have the feeling though that the commit message is pretty clear.
> >>> We'll maybe add that it"s an actual errata.
> >>
> >> Humm, this is not what I meant actually. I only proposed a code source
> >> comment explaining why this is done this way, the current patch summary
> >> looked like it will be perfect between /* */ ;-)
> >
> > I did not want to fill up the source with wordy comments, and settled
> > for a one-liner. I don't know much about the underlying reasons other
> > than the fact that LPDDR1 mode of the controller isn't working properly
> > in self-refresh and that the DDR2 spec is similar enough to work.
> >
> > The one-liner comment says about the same thing, but not with so
> > many words. The comment does make it clear that the switch to DDR2
> > is intentional, and that is all that is needed as protection from some
> > future cleanup. I mean, anyone seeing that comment and just erasing
> > the whole thing without further investigation is not doing a very good
> > job as there is no reason to intentionally switch from LPDDR1 mode to
> > DDR2 mode, other that the fact that the LPDDR1 mode isn't working for
> > some reason. That reason is not to be found in the commit message
> > and I have no information to improve the situation. IMO, the only thing
> > missing is a pointer to the as yet unreleased errata, which should explain
> > the situation clearly for any and all interested parties. May I suggest that
> > someone who cares sends a patch with the comment update when the
> > errata is released?
>
> That's the option that I'll take.
>
> Let's go for it (and anyone remind me if I don't when the errata is
> released).
I fully agree with that, a pointer to a datasheet errata is exactly the
same thing as explaining the issue.
Sylvain
next prev parent reply other threads:[~2015-01-26 16:11 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-26 9:36 [PATCH v2 00/12] AT91 pm cleanup for 3.20 Wenyou Yang
2015-01-26 9:36 ` Wenyou Yang
2015-01-26 9:37 ` [PATCH v2 01/12] pm: at91: pm_slowclock: improve reliability of suspend/resume Wenyou Yang
2015-01-26 9:37 ` Wenyou Yang
2015-01-26 14:54 ` [PATCH v2 0/2] " Sylvain Rochet
2015-01-26 14:54 ` Sylvain Rochet
2015-01-26 14:54 ` [PATCH v2 1/2] pm: at91: pm_slowclock: fix suspend/resume hang up in timeouts Sylvain Rochet
2015-01-26 14:54 ` Sylvain Rochet
2015-01-26 14:54 ` [PATCH v2 2/2] pm: at91: pm_slowclock: remove clocks which are already stopped when entering slow clock mode Sylvain Rochet
2015-01-26 14:54 ` Sylvain Rochet
2015-01-26 9:38 ` [PATCH v2 02/12] pm: at91: Workaround DDRSDRC self-refresh bug with LPDDR1 memories Wenyou Yang
2015-01-26 9:38 ` Wenyou Yang
2015-01-26 10:36 ` Sylvain Rochet
2015-01-26 10:36 ` Sylvain Rochet
2015-01-26 13:34 ` Nicolas Ferre
2015-01-26 13:34 ` Nicolas Ferre
2015-01-26 13:44 ` Sylvain Rochet
2015-01-26 13:44 ` Sylvain Rochet
2015-01-26 15:58 ` Peter Rosin
2015-01-26 15:58 ` Peter Rosin
2015-01-26 16:04 ` Nicolas Ferre
2015-01-26 16:04 ` Nicolas Ferre
2015-01-26 16:11 ` Sylvain Rochet [this message]
2015-01-26 16:11 ` Sylvain Rochet
2015-01-26 9:39 ` [PATCH v2 03/12] pm: at91: pm_slowclock: remove the unused code related with SLOWDOWN_MASTER_CLOCK Wenyou Yang
2015-01-26 9:39 ` Wenyou Yang
2015-01-26 9:40 ` [PATCH v2 04/12] pm: at91: move the copying the sram function to the sram initializationi phase Wenyou Yang
2015-01-26 9:40 ` Wenyou Yang
2015-01-26 12:57 ` Sergei Shtylyov
2015-01-26 12:57 ` Sergei Shtylyov
2015-01-27 3:27 ` Yang, Wenyou
2015-01-27 3:27 ` Yang, Wenyou
2015-01-26 9:40 ` [PATCH v2 05/12] ARM: at91: move select SRAM to ARCH_AT91 Wenyou Yang
2015-01-26 9:40 ` Wenyou Yang
2015-01-26 9:41 ` [PATCH v2 06/12] pm: at91: remove the config item CONFIG_AT91_SLOW_CLOCK Wenyou Yang
2015-01-26 9:41 ` Wenyou Yang
2015-01-26 9:42 ` [PATCH v2 07/12] pm: at91: the standby mode uses the same sram function as the suspend to memory mode Wenyou Yang
2015-01-26 9:42 ` Wenyou Yang
2015-01-26 10:09 ` Sylvain Rochet
2015-01-26 10:09 ` Sylvain Rochet
2015-01-27 4:44 ` Yang, Wenyou
2015-01-27 4:44 ` Yang, Wenyou
2015-01-26 9:42 ` [PATCH v2 08/12] pm: at91: rename file name: pm_slowclock.S -->pm_suspend.S Wenyou Yang
2015-01-26 9:42 ` Wenyou Yang
2015-01-26 9:43 ` [PATCH v2 09/12] pm: at91: rename function name: at91_slow_clock()-->at91_pm_suspend_sram_fn Wenyou Yang
2015-01-26 9:43 ` Wenyou Yang
2015-01-26 9:44 ` [PATCH v2 10/12] pm: at91: remove the at91_xxx_standby() function definitions in the pm.h Wenyou Yang
2015-01-26 9:44 ` Wenyou Yang
2015-01-26 9:45 ` [PATCH v2 11/12] pm: at91: setup: remove the struct ramc_ids .data at91_xxx_standby members Wenyou Yang
2015-01-26 9:45 ` Wenyou Yang
2015-01-26 9:45 ` [PATCH v2 12/12] pm: at91: amend the pm_suspend entry for at91_cpuidle_device Wenyou Yang
2015-01-26 9:45 ` Wenyou Yang
2015-01-26 9:55 ` [PATCH v2 00/12] AT91 pm cleanup for 3.20 Sylvain Rochet
2015-01-26 9:55 ` Sylvain Rochet
2015-01-27 2:58 ` Yang, Wenyou
2015-01-27 2:58 ` Yang, Wenyou
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