linux-kernel - Re: [char-misc-next 3/4] mei: pxp: re-enable client on errors

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Message-ID: <ade96d9edd8bce1bc63dba4e2f1a92517180d774.camel@intel.com>
Date:   Tue, 14 Nov 2023 15:31:34 +0000
From:   "Teres Alexis, Alan Previn" <alan.previn.teres.alexis@...el.com>
To:     "ville.syrjala@...ux.intel.com" <ville.syrjala@...ux.intel.com>,
        "Winkler, Tomas" <tomas.winkler@...el.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Usyskin, Alexander" <alexander.usyskin@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "Lubart, Vitaly" <vitaly.lubart@...el.com>
Subject: Re: [char-misc-next 3/4] mei: pxp: re-enable client on errors

On Tue, 2023-11-14 at 16:00 +0200, Ville Syrjälä wrote:
> On Wed, Oct 11, 2023 at 02:01:56PM +0300, Tomas Winkler wrote:
> > From: Alexander Usyskin <alexander.usyskin@...el.com>
> > 
> > Disable and enable mei-pxp client on errors to clean the internal state.
> 
> This broke i915 on my Alderlake-P laptop.
> 

Hi Alex, i just relooked at the series that got merged, and i noticed
that in patch #3 of the series, you had changed mei_pxp_send_message
to return bytes sent instead of zero on success. IIRC, we had
agreed to not effect the behavior of this component interface (other
than adding the timeout) - this was the intention of Patch #4 that i
was pushing for in order to spec the interface (which continues
to say zero on success). We should fix this to stay with the original
behavior - where mei-pxp should NOT send partial packets and
will only return zero in success case where success is sending of
the complete packets - so we don't need to get back the "bytes sent"
from mei_pxp_send_message. So i think this might be causing the problem.

Side note  to Ville:, are you enabling PXP kernel config by default in
all MESA contexts? I recall that MESA folks were running some CI testing
with enable pxp contexts, but didn't realize this is being enabled by
default in all contexts. Please be aware that enabling pxp-contexts
would temporarily disabled runtime-pm during that contexts lifetime.
Also pxp contexts will be forced to be irrecoverable if it ever hangs.
The former is a hardware architecture requirement but doesn't do anything
if you're enabling display (which I beleive also blocks in ADL). The
latter was a requirement to comply with Vulkan.

...alan