nouveau: properly check for _DSM function support

According to the ACPI spec version 4, section 9.14.1, _DSM functions
must return a value with the first bit enabled if any DSM functions are
supported for the given UUID and revision ID. For a given function index n
to be marked supported, bit n must be enabled.

Signed-off-by: Peter Lekensteyn <lekensteyn@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 22 insertions, 13 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index 525744d593c1..96756d0d6411 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -18,12 +18,6 @@
 
 #include <linux/vga_switcheroo.h>
 
-#define NOUVEAU_DSM_SUPPORTED 0x00
-#define NOUVEAU_DSM_SUPPORTED_FUNCTIONS 0x00
-
-#define NOUVEAU_DSM_ACTIVE 0x01
-#define NOUVEAU_DSM_ACTIVE_QUERY 0x00
-
 #define NOUVEAU_DSM_LED 0x02
 #define NOUVEAU_DSM_LED_STATE 0x00
 #define NOUVEAU_DSM_LED_OFF 0x10
@@ -35,6 +29,7 @@
 #define NOUVEAU_DSM_POWER_SPEED 0x01
 #define NOUVEAU_DSM_POWER_STAMINA 0x02
 
+#define NOUVEAU_DSM_OPTIMUS_FN 0x1A
 static struct nouveau_dsm_priv {
         bool dsm_detected;
         bool optimus_detected;
@@ -148,6 +143,23 @@ static int nouveau_dsm(acpi_handle handle, int func, int arg, uint32_t *result)
         return 0;
 }
 
+/* Returns 1 if a DSM function is usable and 0 otherwise */
+static int nouveau_test_dsm(acpi_handle test_handle,
+        int (*dsm_func)(acpi_handle, int, int, uint32_t *),
+        int sfnc)
+{
+        u32 result = 0;
+
+        /* Function 0 returns a Buffer containing available functions. The args
+         * parameter is ignored for function 0, so just put 0 in it */
+        if (dsm_func(test_handle, 0, 0, &result))
+                return 0;
+
+        /* ACPI Spec v4 9.14.1: if bit 0 is zero, no function is supported. If
+         * the n-th bit is enabled, function n is supported */
+        return result & 1 && result & (1 << sfnc);
+}
+
 static int nouveau_dsm_switch_mux(acpi_handle handle, int mux_id)
 {
         mxm_wmi_call_mxmx(mux_id == NOUVEAU_DSM_LED_STAMINA ? MXM_MXDS_ADAPTER_IGD : MXM_MXDS_ADAPTER_0);
@@ -212,8 +224,7 @@ static int nouveau_dsm_pci_probe(struct pci_dev *pdev)
 {
         acpi_handle dhandle, nvidia_handle;
         acpi_status status;
-        int ret, retval = 0;
-        uint32_t result;
+        int retval = 0;
 
         dhandle = DEVICE_ACPI_HANDLE(&pdev->dev);
         if (!dhandle)
@@ -224,13 +235,11 @@ static int nouveau_dsm_pci_probe(struct pci_dev *pdev)
                 return false;
         }
 
-        ret = nouveau_dsm(dhandle, NOUVEAU_DSM_SUPPORTED,
-                          NOUVEAU_DSM_SUPPORTED_FUNCTIONS, &result);
-        if (ret == 0)
+        if (nouveau_test_dsm(dhandle, nouveau_dsm, NOUVEAU_DSM_POWER))
                 retval |= NOUVEAU_DSM_HAS_MUX;
 
-        ret = nouveau_optimus_dsm(dhandle, 0, 0, &result);
-        if (ret == 0)
+        if (nouveau_test_dsm(dhandle, nouveau_optimus_dsm,
+                NOUVEAU_DSM_OPTIMUS_FN))
                 retval |= NOUVEAU_DSM_HAS_OPT;
 
         if (retval)