From: Daniel Kurtz <djkurtz@chromium.org>
To: Henry Chen <HenryC.Chen@mediatek.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
Mark Brown <broonie@kernel.org>
Cc: "Sascha Hauer" <kernel@pengutronix.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-mediatek@lists.infradead.org,
"Eddie Huang (黃智傑)" <eddie.huang@mediatek.com>,
"Kevin Hilman" <khilman@kernel.org>
Subject: Re: [PATCH] regmap: Add function check before called format_val
Date: Wed, 12 Aug 2015 22:20:57 +0800 [thread overview]
Message-ID: <CAGS+omDa+FhKD2u_VwBG3cWvN+ZiHneqFVz=mtdYuPsiQu4JEQ@mail.gmail.com> (raw)
In-Reply-To: <1437458845.30329.51.camel@mtksdaap41>
Hi Henry & Mark,
On Tue, Jul 21, 2015 at 2:07 PM, Henry Chen <HenryC.Chen@mediatek.com> wrote:
> On Mon, 2015-07-20 at 16:02 +0100, Mark Brown wrote:
>> On Mon, Jul 20, 2015 at 08:41:50PM +0800, Henry Chen wrote:
>> > The regmap_format will not be initialize since regmap_bus is not assgined
>> > on regmap_init(). It should has a function check before using
>> > format_val() to avoid null function called on regmap_bulk_read().
>>
>> > - map->format.format_val(val + (i * val_bytes), ival, 0);
>> > + if (map->format.format_val)
>> > + map->format.format_val(val + (i * val_bytes), ival, 0);
>> > + else
>> > + memcpy(val + (i * val_bytes), &ival, val_bytes);
>>
>> Your changelog doesn't explan why we are in this code path in the first
>> place without a format_val() and why a memcpy() is an appropriate
>> replacement. It should, it's not clear to me that this is a good fix
>> but I don't feel I fully understand the problem.
>
> Sorry for being unclear for issue, the call flow as following,
>
> First, in drivers/mfd/mtk_pmic_wrap.c which registered regmap without
> rebmap_bus.
> devm_regmap_init(wrp->dev, NULL, wrp, &pwrap_regmap_config);
>
> It call to regmap_init() and go to "skip_format_initialization" because
> regmap_bus didn't assign by driver.
>
> if (!bus) {
> map->reg_read = config->reg_read;
> map->reg_write = config->reg_write;
>
> map->defer_caching = false;
> goto skip_format_initialization;"
>
> Then in driver rtc-mt6397.c, it used regmap_bulk_read() to get the time
> of PMIC, and hit the null function of format_val(), because the
> regmap_bus was null.
>
> It skipped the initialization of format_val() because bus == null, but
> called the format_val() at regmap_bulk_read() if bus == null.
>
> Maybe it was not the good fix for this, but should be a problem need to
> be reported, or should I need to give the regmap_bus on mtk_pmic_wrap.c?
I ran into this bug when testing Matthias' v4.2-next/for-next branch
on mt8173. It now crashes on boot.
Since I didn't see it elsewhere in this discussion, I'll point out
that the "regression" here was introduced by commit [0], which added
the call to map->format.format_val from regmap_bulk_read() when
map->bus == NULL.
[0] commit 15b8d2c41fe5839582029f65c5f7004db451cc2b
Author: Arun Chandran <achandran@mvista.com>
regmap: Fix regmap_bulk_read in BE mode
Perhaps the easiest work around to unbreak v4.2 is, as Henry mentions,
for mtk_pmic_wrap to define its own regmap_bus, with .read() &
.write() handlers. This way they will inherit the default built-in
format_val() from the regmap core.
Making mtk_pmic-wrap into a regmap_bus makes a bit of sense
architecturally, too, since it is essentially just a bus for accessing
the registers of an off-chip PMIC. The CPU sees a platform bus, but
the registers of the remote PMIC are accessed over a dedicated SPI
bus.
WDYT?
Henry, can you try to implement this?
Thanks,
-Dan
next prev parent reply other threads:[~2015-08-12 14:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-20 12:41 [PATCH] regmap: Add function check before called format_val Henry Chen
2015-07-20 15:02 ` Mark Brown
2015-07-21 6:07 ` Henry Chen
2015-07-21 17:25 ` Mark Brown
2015-07-22 14:31 ` Henry Chen
2015-07-22 17:00 ` Mark Brown
2015-08-12 14:20 ` Daniel Kurtz [this message]
2015-08-13 15:25 ` Henry Chen
2015-08-14 17:56 ` Mark Brown
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAGS+omDa+FhKD2u_VwBG3cWvN+ZiHneqFVz=mtdYuPsiQu4JEQ@mail.gmail.com' \
--to=djkurtz@chromium.org \
--cc=HenryC.Chen@mediatek.com \
--cc=broonie@kernel.org \
--cc=eddie.huang@mediatek.com \
--cc=kernel@pengutronix.de \
--cc=khilman@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=matthias.bgg@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).