[Intel-gfx] [PATCH] drm/i915: Switch TGL-H DP-IN to dGFX when it's supported

[Kai-Heng Feng]

On mobile workstations like HP ZBook Fury G8, iGFX's DP-IN can switch to
dGFX so external monitors are routed to dGFX, and more monitors can be
supported as result.

To switch the DP-IN to dGFX, the driver needs to invoke _DSM function 20
on intel_dsm_guid2. This method is described in Intel document 632107.

Signed-off-by: Kai-Heng Feng <kai.heng.f...@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_acpi.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c 
b/drivers/gpu/drm/i915/display/intel_acpi.c
index e78430001f077..3bd5930e2769b 100644
--- a/drivers/gpu/drm/i915/display/intel_acpi.c
+++ b/drivers/gpu/drm/i915/display/intel_acpi.c
@@ -20,6 +20,7 @@ static const guid_t intel_dsm_guid =
                  0xa8, 0x54, 0x0f, 0x13, 0x17, 0xb0, 0x1c, 0x2c);
 
 #define INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED 0 /* No args */
+#define INTEL_DSM_FN_DP_IN_SWITCH_TO_DGFX 20 /* No args */
 
 static const guid_t intel_dsm_guid2 =
        GUID_INIT(0x3e5b41c6, 0xeb1d, 0x4260,
@@ -187,6 +188,7 @@ void intel_dsm_get_bios_data_funcs_supported(struct 
drm_i915_private *i915)
        struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
        acpi_handle dhandle;
        union acpi_object *obj;
+       int supported = 0;
 
        dhandle = ACPI_HANDLE(&pdev->dev);
        if (!dhandle)
@@ -194,8 +196,22 @@ void intel_dsm_get_bios_data_funcs_supported(struct 
drm_i915_private *i915)
 
        obj = acpi_evaluate_dsm(dhandle, &intel_dsm_guid2, 
INTEL_DSM_REVISION_ID,
                                INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED, 
NULL);
-       if (obj)
+       if (obj) {
+               if (obj->type == ACPI_TYPE_INTEGER)
+                       supported = obj->integer.value;
+
                ACPI_FREE(obj);
+       }
+
+       /* Tiger Lake H DP-IN Boot Time Switching from iGfx to dGfx */
+       if (supported & BIT(20)) {
+               obj = acpi_evaluate_dsm(dhandle, &intel_dsm_guid2,
+                                       INTEL_DSM_REVISION_ID,
+                                       INTEL_DSM_FN_DP_IN_SWITCH_TO_DGFX,
+                                       NULL);
+               if (obj)
+                       ACPI_FREE(obj);
+       }
 }
 
 /*
-- 
2.36.1