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Subject: Re: [PATCH] RFC: ACPI / OSI: remove workarounds for hybrid graphics
 laptops
To:     Karol Herbst <kherbst@redhat.com>, linux-acpi@vger.kernel.org
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>, Lyude Paul <lyude@redhat.com>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        nouveau@lists.freedesktop.org
References: <20200717190547.648604-1-kherbst@redhat.com>
From:   Alex Hung <alex.hung@canonical.com>
Message-ID: <e7a8cb3a-e9f8-b78a-93f0-c09e5eb5ed10@canonical.com>
Date:   Fri, 17 Jul 2020 13:52:12 -0600
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On 2020-07-17 1:05 p.m., Karol Herbst wrote:
> It's hard to figure out what systems are actually affected and right now I
> don't see a good way of removing those...
> 
> But I'd like to see thos getting removed and drivers fixed instead (which
> happened at least for nouveau).
> 
> And as mentioned before, I prefer people working on fixing issues instead
> of spending time to add firmware level workarounds which are hard to know
> to which systems they apply to, hard to remove and basically a big huge
> pain to work with.> In the end I have no idea how to even figure out what systems are affected
> and which not by this, so I have no idea how to even verify we can safely
> remove this (which just means those are impossible to remove unless we risk
> breaking systems, which again makes those supper annoying to deal with).
> 
> Also from the comments it's hard to get what those bits really do. Are they
> just preventing runtime pm or do the devices are powered down when booting?
> I am sure it's the former, still...
> 
> Please, don't do this again.
> 
> For now, those workaround prevent power savings on systems those workaround
> applies to, which might be any so those should get removed asap and if
> new issues arrise removing those please do a proper bug report and we can
> look into it and come up with a proper fix (and keep this patch out until
> we resolve all of those).
> 
> Signed-off-by: Karol Herbst <kherbst@redhat.com>
> CC: Alex Hung <alex.hung@canonical.com>
> CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> CC: Len Brown <lenb@kernel.org>
> CC: Lyude Paul <lyude@redhat.com>
> CC: linux-kernel@vger.kernel.org
> CC: dri-devel@lists.freedesktop.org
> CC: nouveau@lists.freedesktop.org
> ---
>  drivers/acpi/osi.c | 24 ------------------------
>  1 file changed, 24 deletions(-)
> 
> diff --git a/drivers/acpi/osi.c b/drivers/acpi/osi.c
> index 9f68538091384..d4405e1ca9b97 100644
> --- a/drivers/acpi/osi.c
> +++ b/drivers/acpi/osi.c
> @@ -44,30 +44,6 @@ osi_setup_entries[OSI_STRING_ENTRIES_MAX] __initdata = {
>  	{"Processor Device", true},
>  	{"3.0 _SCP Extensions", true},
>  	{"Processor Aggregator Device", true},
> -	/*
> -	 * Linux-Dell-Video is used by BIOS to disable RTD3 for NVidia graphics
> -	 * cards as RTD3 is not supported by drivers now.  Systems with NVidia
> -	 * cards will hang without RTD3 disabled.
> -	 *
> -	 * Once NVidia drivers officially support RTD3, this _OSI strings can
> -	 * be removed if both new and old graphics cards are supported.
> -	 */
> -	{"Linux-Dell-Video", true},
> -	/*
> -	 * Linux-Lenovo-NV-HDMI-Audio is used by BIOS to power on NVidia's HDMI
> -	 * audio device which is turned off for power-saving in Windows OS.
> -	 * This power management feature observed on some Lenovo Thinkpad
> -	 * systems which will not be able to output audio via HDMI without
> -	 * a BIOS workaround.
> -	 */
> -	{"Linux-Lenovo-NV-HDMI-Audio", true},
> -	/*
> -	 * Linux-HPI-Hybrid-Graphics is used by BIOS to enable dGPU to
> -	 * output video directly to external monitors on HP Inc. mobile
> -	 * workstations as Nvidia and AMD VGA drivers provide limited
> -	 * hybrid graphics supports.
> -	 */
> -	{"Linux-HPI-Hybrid-Graphics", true},
>  };
>  
>  static u32 acpi_osi_handler(acpi_string interface, u32 supported)
> 

The changes were discussed and tested a while ago, and no crashes were
observed. Thanks for solving PM issues in nouveau.

Acked-by: Alex Hung <alex.hung@canonical.com>