drm/i915/skl: Add the additional graphics stolen sizes

Skylake introduces new stolen memory sizes starting at 0xf0 (4MB) and
growing by 4MB increments from there.

v2: Rebase on top of the early-quirk changes from Ville.

v3: Rebase on top of the PCI_IDS/IDS macro rename

Reviewed-by: Thomas Wood <thomas.wood@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

arch/x86/kernel/early-quirks.c

@@ -455,6 +455,23 @@ struct intel_stolen_funcs {
 	u32 (*base)(int num, int slot, int func, size_t size);
 };
 
+static size_t __init gen9_stolen_size(int num, int slot, int func)
+{
+	u16 gmch_ctrl;
+
+	gmch_ctrl = read_pci_config_16(num, slot, func, SNB_GMCH_CTRL);
+	gmch_ctrl >>= BDW_GMCH_GMS_SHIFT;
+	gmch_ctrl &= BDW_GMCH_GMS_MASK;
+
+	if (gmch_ctrl < 0xf0)
+		return gmch_ctrl << 25; /* 32 MB units */
+	else
+		/* 4MB increments starting at 0xf0 for 4MB */
+		return (gmch_ctrl - 0xf0 + 1) << 22;
+}
+
+typedef size_t (*stolen_size_fn)(int num, int slot, int func);
+
 static const struct intel_stolen_funcs i830_stolen_funcs __initconst = {
 	.base = i830_stolen_base,
 	.size = i830_stolen_size,
@@ -490,6 +507,11 @@ static const struct intel_stolen_funcs gen8_stolen_funcs __initconst = {
 	.size = gen8_stolen_size,
 };
 
+static const struct intel_stolen_funcs gen9_stolen_funcs __initconst = {
+	.base = intel_stolen_base,
+	.size = gen9_stolen_size,
+};
+
 static const struct intel_stolen_funcs chv_stolen_funcs __initconst = {
 	.base = intel_stolen_base,
 	.size = chv_stolen_size,
@@ -523,6 +545,7 @@ static const struct pci_device_id intel_stolen_ids[] __initconst = {
 	INTEL_BDW_M_IDS(&gen8_stolen_funcs),
 	INTEL_BDW_D_IDS(&gen8_stolen_funcs),
 	INTEL_CHV_IDS(&chv_stolen_funcs),
+	INTEL_SKL_IDS(&gen9_stolen_funcs),
 };
 
 static void __init intel_graphics_stolen(int num, int slot, int func)