linux-kernel - Re: i2c-designware: NULL ptr at RIP: 0010:regmap

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Date: Sat, 6 Jan 2024 18:06:23 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc: "V, Narasimhan" <Narasimhan.V@....com>, Borislav Petkov <bp@...en8.de>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Jan Dabros <jsd@...ihalf.com>, Andi Shyti <andi.shyti@...nel.org>,
	"Limonciello, Mario" <Mario.Limonciello@....com>
Subject: Re: i2c-designware: NULL ptr at RIP: 0010:regmap_read+0x12/0x70

On Thu, Jan 04, 2024 at 03:40:44PM +0200, Jarkko Nikula wrote:
> On 1/4/24 08:35, V, Narasimhan wrote:
> > > [    6.245173] i2c_designware AMDI0010:00: Unknown Synopsys component type: 0xffffffff
> > 
> > This made me scratching my head since driver probing will fail in this
> > case with -ENODEV and I could not trigger runtime PM activity in such
> > case but perhaps this is timing specific which happens to happen in your
> > case.
> > 
> > Out of curiosity do you see this same "i2c_designware AMDI0010:00:
> > Unknown Synopsys component type: 0xffffffff" error on Vanilla or is it
> > also regression in linux-next?
> > 
> > This does not happen on Vanilla, only on linux-next.
> > 
> This is even more strange. Controller is in reset but I'm blind to see from
> Andy's patches why. Do you have change to test at these commits?
> 
> bd466a892612 ("i2c: designware: Fix PM calls order in dw_i2c_plat_probe()")
> c012fde343d2 ("i2c: designware: Fix reset call order in dw_i2c_plat_probe()"
> 
> and maybe the last one
> 4bff054b64e1 ("i2c: designware: Fix spelling and other issues in the
> comments")
> 
> I'm trying to narrow does the regression come from first two patches and if
> not, then test the last one.
> 
> Andy is out of office and if we can narrow the regression to first two
> patches we perhaps can revert just them and otherwise need to drop the whole
> set.

Since I saw this email...

First of all, it's easy just to go patch-by-patch and see if it helps.
Or simple bisect among 24 commits (4 iterations only).

Second, it seems that we are using autosuspend but we don't prevent
the PM to go down during the ->probe(). So, a WA can be to take a reference
count preventing PM from going down.

->remove, for instance, uses RPM get/put calls.

-- 
With Best Regards,
Andy Shevchenko