From: Peter Rosin <peda@axentia.se>
To: Sylvain Rochet <sylvain.rochet@finsecur.com>,
Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: 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 15:58:44 +0000 [thread overview]
Message-ID: <372b731350484f8ea1d29bd016421dfb@EMAIL.axentia.se> (raw)
In-Reply-To: <20150126134453.GA27559@gradator.net>
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 2147 bytes --]
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?
If others feel differently, by all means please reword and expand the
comment.
Cheers,
Peter
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WARNING: multiple messages have this Message-ID (diff)
From: peda@axentia.se (Peter Rosin)
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 15:58:44 +0000 [thread overview]
Message-ID: <372b731350484f8ea1d29bd016421dfb@EMAIL.axentia.se> (raw)
In-Reply-To: <20150126134453.GA27559@gradator.net>
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?
If others feel differently, by all means please reword and expand the
comment.
Cheers,
Peter
next prev parent reply other threads:[~2015-01-26 15:58 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 [this message]
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
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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