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.
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.
Kai-Heng
+ dell_switchable_gfx_enabled_func =
+ symbol_request(dell_switchable_gfx_enabled);
+ if (!dell_switchable_gfx_enabled_func)
+ return false;
+
+ err = dell_switchable_gfx_enabled_func(&enabled);
+
+ symbol_put(dell_switchable_gfx_enabled);
+
+ return !err ? enabled : false;
+}
+#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)
{
@@ -1702,6 +1732,11 @@ 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);
--
Pali Rohár
pali.rohar@xxxxxxxxx
