linux-kernel - Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode.

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Message-Id: <201504110114.45676@pali>
Date:	Sat, 11 Apr 2015 01:14:45 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Mario Limonciello <mario_limonciello@...l.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
Subject: Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode.

On Saturday 11 April 2015 01:07:03 Mario Limonciello wrote:
> On 04/10/2015 05:39 PM, Pali Rohár wrote:
> > On Wednesday 25 February 2015 21:45:22 Pali Rohár wrote:
> > Hello Mario,
> > have you patched synaptics driver with some resetafter
> > parameter? And have some team in dell found reason for
> > invalid packets?
> 
> Hi Pali,
> 
> The reason was found for the invalid packets in PS2 mode, but
> I can't go into the details about it publicly.
> 
> I think it's better to not bother including my proposed
> solution, however.  The vector of users in PS2 mode should be
> very small now. Here's why:
> With no kernel command line options applied the touchpad will
> run in I2C mode with the current kernel.  The only reason
> that users were being exposed to the PS2 mode was if they ran
> with the kernel command line option acpi_osi="!Windows 2013".
>  This was required with BIOS A01 due to the problem with I2S
> audio.  This I2S audio problem has been resolved for BIOS A02
> and BIOS A03.  With no options applied on the kernel command
> line the system will run in I2C touchpad and HDA audio. All
> new machines will be coming with A03 or later.  Users with
> earlier versions have been advised to upgrade to fix this
> among other issues.
> 
> The HDA audio will work correctly for output with 4.0.  It
> will work properly for input when these two patches are
> applied (which will land in 4.1)
> 
> https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/c
> ommit/?h=for-next&id=e1e62b98ebddc3234f3259019d3236f66fc667f8
> 
> and
> 
> https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/c
> ommit/?h=for-next&id=f3b703326541d0c1ce85f5e570f6d2b6bd4296ec
> 
> 
> If the patch to disambiguate the value of _REV() lands in 4.1
> the audio will begin to operate fully in I2S mode and the
> necessary support will be included in 4.1 as well.
> 
> So with all those factors I feel that it's a very low risk
> that users will end up in PS2 mode with the current
> development focus kernels.
> 
> Thanks,

I could see problem with using older kernels which are in more 
stable or LTS distribution versions...

But it is nice that problems are fixes for future 4.0/4.1 
versions.

And if you located reason for invalid packets in PS/2 mode, will 
you fix it in some new bios versions?

Can you comment if this is also same problem with invalid packets 
on E6440/E7440 machines?

-- 
Pali Rohár
pali.rohar@...il.com

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