linux-kernel - Re: [PATCH v3 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics

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Date:   Thu, 12 Apr 2018 12:50:02 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Kai-Heng Feng" <kai.heng.feng@...onical.com>
Cc:     Lukas Wunner <lukas@...ner.de>, <mario.limonciello@...l.com>,
        <pali.rohar@...il.com>, <andy@...radead.org>,
        <dvhart@...radead.org>, <mjg59@...f.ucam.org>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics

On Thu, 12 Apr 2018 12:42:39 +0200,
Kai-Heng Feng wrote:
> 
> Some Dell platforms (Preicsion 7510/7710/7520/7720) have a BIOS option
> "Switchable Graphics" (SG).
> 
> When SG is enabled, we have:
> 00:02.0 VGA compatible controller: Intel Corporation Device 591b (rev 04)
> 00:1f.3 Audio device: Intel Corporation CM238 HD Audio Controller (rev 31)
> 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc.  [AMD/ATI] Ellesmere [Polaris10]
> 01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 580]
> 
> The Intel Audio outputs all the sound, including HDMI audio. The audio
> controller comes with AMD graphics doesn't get used.
> 
> When SG is disabled, we have:
> 00:1f.3 Audio device: Intel Corporation CM238 HD Audio Controller (rev 31)
> 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc.  [AMD/ATI] Ellesmere [Polaris10]
> 01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 580]
> 
> Now it's a typical discrete-only system. HDMI audio comes from AMD audio
> controller, others from Intel audio controller.
> 
> When SG is enabled, the unused AMD audio controller still exposes its
> sysfs, so userspace still opens the control file and stream. If
> userspace tries to output sound through the stream, it hangs when
> runtime suspend kicks in:
> [ 12.796265] snd_hda_intel 0000:01:00.1: Disabling via vga_switcheroo
> [ 12.796367] snd_hda_intel 0000:01:00.1: Cannot lock devices!
> 
> Since the discrete audio controller isn't useful when SG enabled, we
> should just disable the device.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

Adding Lukas to Cc.

I thought we manage this better now with runtime PM by Lukas's recent
patchset?


thanks,

Takashi

> ---
> v3: Simplify dell_switchable_gfx_is_enabled() by returning bool instead
>     of error code.
>     Use DMI_DEV_TYPE_OEM_STRING to match Dell System.
> 
> v2: Mario suggested to squash the HDA part into the same series.
> 
>  sound/pci/hda/hda_intel.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> index 7720e3102bcc..d9310616d5ca 100644
> --- a/sound/pci/hda/hda_intel.c
> +++ b/sound/pci/hda/hda_intel.c
> @@ -49,6 +49,8 @@
>  #include <linux/clocksource.h>
>  #include <linux/time.h>
>  #include <linux/completion.h>
> +#include <linux/dell-common.h>
> +#include <linux/dmi.h>
>  
>  #ifdef CONFIG_X86
>  /* for snoop control */
> @@ -1629,6 +1631,38 @@ static void check_msi(struct azx *chip)
>  	}
>  }
>  
> +#if IS_ENABLED(CONFIG_DELL_LAPTOP)
> +static bool check_dell_switchable_gfx(struct pci_dev *pdev)
> +{
> +	bool (*dell_switchable_gfx_is_enabled_func)(void);
> +	bool enabled;
> +
> +	/* Only need to check for Dell laptops and AIOs */
> +	if (!dmi_find_device(DMI_DEV_TYPE_OEM_STRING, "Dell System", NULL) ||
> +	    !(dmi_match(DMI_CHASSIS_TYPE, "10") ||
> +	      dmi_match(DMI_CHASSIS_TYPE, "13")) ||
> +	    !(pdev->vendor == PCI_VENDOR_ID_ATI ||
> +	      pdev->vendor == PCI_VENDOR_ID_NVIDIA))
> +		return false;
> +
> +	dell_switchable_gfx_is_enabled_func =
> +		symbol_request(dell_switchable_gfx_is_enabled);
> +	if (!dell_switchable_gfx_is_enabled_func)
> +		return false;
> +
> +	enabled = dell_switchable_gfx_is_enabled_func();
> +
> +	symbol_put(dell_switchable_gfx_is_enabled);
> +
> +	return enabled;
> +}
> +#else
> +static bool check_dell_switchable_gfx(struct pci_dev *pdev)
> +{
> +	return false;
> +}
> +#endif
> +
>  /* check the snoop mode availability */
>  static void azx_check_snoop_available(struct azx *chip)
>  {
> @@ -1711,6 +1745,11 @@ static int azx_create(struct snd_card *card, struct pci_dev *pci,
>  	if (err < 0)
>  		return err;
>  
> +	if (check_dell_switchable_gfx(pci)) {
> +		pci_disable_device(pci);
> +		return -ENODEV;
> +	}
> +
>  	hda = kzalloc(sizeof(*hda), GFP_KERNEL);
>  	if (!hda) {
>  		pci_disable_device(pci);
> -- 
> 2.17.0
> 
>