> -----Original Message----- > From: Kai Heng Feng [mailto:kai.heng.feng@xxxxxxxxxxxxx] > Sent: Friday, March 9, 2018 5:30 PM > To: Pali Rohár <pali.rohar@xxxxxxxxx> > Cc: mjg59@xxxxxxxxxxxxx; dvhart@xxxxxxxxxxxxx; andy@xxxxxxxxxxxxx; > Limonciello, Mario <Mario_Limonciello@xxxxxxxx>; tiwai@xxxxxxxx; platform- > driver-x86@xxxxxxxxxxxxxxx; Linux Kernel Mailing List <linux- > kernel@xxxxxxxxxxxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx > Subject: Re: [PATCH v2 3/3] ALSA: hda: Disabled unused audio controller for Dell > platforms with Switchable Graphics > > > > On Mar 9, 2018, at 5:02 PM, Pali Rohár <pali.rohar@xxxxxxxxx> wrote: > > > > On Thursday 08 March 2018 17:10:23 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@xxxxxxxxxxxxx> > >> --- > >> v2: Mario suggested to squash the HDA part into the same series. > >> > >> sound/pci/hda/hda_intel.c | 35 +++++++++++++++++++++++++++++++++++ > >> 1 file changed, 35 insertions(+) > >> > >> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c > >> index 96143df19b21..8e3e8b88624a 100644 > >> --- a/sound/pci/hda/hda_intel.c > >> +++ b/sound/pci/hda/hda_intel.c > >> @@ -49,6 +49,7 @@ > >> #include <linux/clocksource.h> > >> #include <linux/time.h> > >> #include <linux/completion.h> > >> +#include <linux/dell-common.h> > >> > >> #ifdef CONFIG_X86 > >> /* for snoop control */ > >> @@ -1620,6 +1621,35 @@ static void check_msi(struct azx *chip) > >> } > >> } > >> > >> +#if IS_ENABLED(CONFIG_DELL_LAPTOP) > >> +static bool check_dell_switchable_gfx(struct pci_dev *pdev) > >> +{ > >> + static int (*dell_switchable_gfx_enabled_func)(bool *); > >> + bool enabled; > >> + int err; > >> + > >> + if (pdev->vendor != PCI_VENDOR_ID_ATI || > >> + pdev->subsystem_vendor != PCI_VENDOR_ID_DELL) > >> + return false; > > > > Are you sure that you want to do this check unconditionally on all > > machines which have enabled CONFIG_DELL_LAPTOP? > > > > Subvendor ID_DELL for dell specific code is not suspicious, but ID_ATI > > is. What would happen if ATI vendor changes to NVIDIA or other which is > > not related to Dell? > > We only check it when it's both ATI and DELL, otherwise just return false? > > The platform does have a NVIDIA variant, but the discrete NVIDIA have a > audio controller, hence it doesn't have the issue. > The issue only happens to AMD/ATI configs with "Switchable Graphics" option. > Pali is your concern that this code for matching vendor/subsystem is running on non-Dell too? The only other recommendation I think that can be to restrict to matching Dell OEM strings in SMBIOS table, but I don't think that's any better than the matching for VID/SSVID. > > > > Interesting question would be, how handle this situation Windows? > > I don't know how this platform handles this on Windows, I guess we need > Mario to shed some lights here. Sorry I don't have this information to share. I don't think it's too useful here anyway though because Windows driver architecture is much different in this area.
