drm/radeon/kms: enable ACPI powermanagement mode on radeon gpus.

Some GPUs have an APM/ACPI PM mode selection switch and some BIOSes
set this to APM. We really want this in ACPI mode for Linux.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/r100.c

@@ -1809,6 +1809,7 @@ void r100_set_common_regs(struct radeon_device *rdev)
 {
 	struct drm_device *dev = rdev->ddev;
 	bool force_dac2 = false;
+	u32 tmp;
 
 	/* set these so they don't interfere with anything */
 	WREG32(RADEON_OV0_SCALE_CNTL, 0);
@@ -1880,6 +1881,12 @@ void r100_set_common_regs(struct radeon_device *rdev)
 		WREG32(RADEON_DISP_HW_DEBUG, disp_hw_debug);
 		WREG32(RADEON_DAC_CNTL2, dac2_cntl);
 	}
+
+	/* switch PM block to ACPI mode */
+	tmp = RREG32_PLL(RADEON_PLL_PWRMGT_CNTL);
+	tmp &= ~RADEON_PM_MODE_SEL;
+	WREG32_PLL(RADEON_PLL_PWRMGT_CNTL, tmp);
+
 }
 
 /*

drivers/gpu/drm/radeon/radeon_reg.h

@@ -346,6 +346,7 @@
 #       define RADEON_TVPLL_PWRMGT_OFF      (1 << 30)
 #       define RADEON_TVCLK_TURNOFF         (1 << 31)
 #define RADEON_PLL_PWRMGT_CNTL              0x0015 /* PLL */
+#	define RADEON_PM_MODE_SEL           (1 << 13)
 #       define RADEON_TCL_BYPASS_DISABLE    (1 << 20)
 #define RADEON_CLR_CMP_CLR_3D               0x1a24
 #define RADEON_CLR_CMP_CLR_DST              0x15c8