linux-kernel - Re: [PATCH] drm/msm/dp: add module parameter for PSR

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Message-ID: <ZGzalLjTvUfzEADU@hovoldconsulting.com>
Date:   Tue, 23 May 2023 17:24:04 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        freedreno@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, quic_jesszhan@...cinc.com,
        swboyd@...omium.org, dianders@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: add module parameter for PSR

On Fri, May 12, 2023 at 09:13:04PM +0300, Dmitry Baryshkov wrote:
> On 28/04/2023 02:28, Abhinav Kumar wrote:
> > On sc7280 where eDP is the primary display, PSR is causing
> > IGT breakage even for basic test cases like kms_atomic and
> > kms_atomic_transition. Most often the issue starts with below
> > stack so providing that as reference
> > 
> > Call trace:
> >   dpu_encoder_assign_crtc+0x64/0x6c
> >   dpu_crtc_enable+0x188/0x204
> >   drm_atomic_helper_commit_modeset_enables+0xc0/0x274
> >   msm_atomic_commit_tail+0x1a8/0x68c
> >   commit_tail+0xb0/0x160
> >   drm_atomic_helper_commit+0x11c/0x124
> >   drm_atomic_commit+0xb0/0xdc
> >   drm_atomic_connector_commit_dpms+0xf4/0x110
> >   drm_mode_obj_set_property_ioctl+0x16c/0x3b0
> >   drm_connector_property_set_ioctl+0x4c/0x74
> >   drm_ioctl_kernel+0xec/0x15c
> >   drm_ioctl+0x264/0x408
> >   __arm64_sys_ioctl+0x9c/0xd4
> >   invoke_syscall+0x4c/0x110
> >   el0_svc_common+0x94/0xfc
> >   do_el0_svc+0x3c/0xb0
> >   el0_svc+0x2c/0x7c
> >   el0t_64_sync_handler+0x48/0x114
> >   el0t_64_sync+0x190/0x194
> > ---[ end trace 0000000000000000 ]---
> > [drm-dp] dp_ctrl_push_idle: PUSH_IDLE pattern timedout
> > 
> > Other basic use-cases still seem to work fine hence add a
> > a module parameter to allow toggling psr enable/disable till
> > PSR related issues are hashed out with IGT.
> 
> For the reference: Bjorn reported that he has issues with VT on a 
> PSR-enabled laptops. This patch fixes the issue for him

Module parameters are almost never warranted, and it is definitely not
the right way to handle a broken implementation.

I've just sent a revert that unconditionally disables PSR support until
the implementation has been fixed:

	https://lore.kernel.org/lkml/20230523151646.28366-1-johan+linaro@kernel.org/

Johan