[PATCH 1/2] drm/amdgpu: fix power state when port pm is unavailable

[Peter Wu]

When PCIe port PM is not enabled (system BIOS is pre-2015 or the
pcie_port_pm=off parameter is set), legacy ATPX PM should still be
marked as supported. Otherwise the GPU can fail to power on after
runtime suspend. This affected a Dell Inspiron 5548.

Ideally the BIOS date in the PCI core is lowered to 2013 (the first year
where hybrid graphics platforms using power resources was introduced),
but that seems more risky at this point and would not solve the
pcie_port_pm=off issue.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98505
Reported-and-tested-by: Nayan Deshmukh <nayan26deshmukh at gmail.com>
Signed-off-by: Peter Wu <peter at lekensteyn.nl>
---
Hi,

This patch is already three weeks old. One alternative idea was lowering BIOS
date in PCI core, but as pcie_port_pm=force did not have the desired effect, I
do not think that this would help though.

I have also not contacted linux-pci or Mika about lowering the year due to the
lack of a good reason.  Might do it later though once ACPICA bug 1333 is sorted
out such that lowering the year actually has benefits for a Nvidia laptop (or if
some amdgpu problem can be solved by this).

Both patches should probably be Cc stable (4.8+), fixing 2f5af82eeab2 and
b8c9fd5ad4b4 ("track whether if this is a hybrid graphics platform"). There have
been some ifdef 0's and reverts in between, so I was not sure if adding the
Fixes tag is appropriate.

Kind regards,
Peter
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c
index 10b5ddf..951addf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c
@@ -33,6 +33,7 @@ struct amdgpu_atpx {
 
 static struct amdgpu_atpx_priv {
 	bool atpx_detected;
+	bool bridge_pm_usable;
 	/* handle for device - and atpx */
 	acpi_handle dhandle;
 	acpi_handle other_handle;
@@ -200,7 +201,11 @@ static int amdgpu_atpx_validate(struct amdgpu_atpx *atpx)
 	atpx->is_hybrid = false;
 	if (valid_bits & ATPX_MS_HYBRID_GFX_SUPPORTED) {
 		printk("ATPX Hybrid Graphics\n");
-		atpx->functions.power_cntl = false;
+		/*
+		 * Disable legacy PM methods only when pcie port PM is usable,
+		 * otherwise the device might fail to power off or power on.
+		 */
+		atpx->functions.power_cntl = !amdgpu_atpx_priv.bridge_pm_usable;
 		atpx->is_hybrid = true;
 	}
 
@@ -471,6 +476,7 @@ static int amdgpu_atpx_power_state(enum vga_switcheroo_client_id id,
  */
 static bool amdgpu_atpx_pci_probe_handle(struct pci_dev *pdev)
 {
+	struct pci_dev *parent_pdev = pci_upstream_bridge(pdev);
 	acpi_handle dhandle, atpx_handle;
 	acpi_status status;
 
@@ -485,6 +491,7 @@ static bool amdgpu_atpx_pci_probe_handle(struct pci_dev *pdev)
 	}
 	amdgpu_atpx_priv.dhandle = dhandle;
 	amdgpu_atpx_priv.atpx.handle = atpx_handle;
+	amdgpu_atpx_priv.bridge_pm_usable = parent_pdev && parent_pdev->bridge_d3;
 	return true;
 }
 
-- 
2.10.2