drm/nouveau/bios: fix OF loading

Currently OF bios load fails for a few reasons:
 - checksum failure
 - bios size too small
 - no PCIR header
 - bios length not a multiple of 4

In this change, we resolve all of the above by ignoring any checksum
failures (since OF VBIOS tends not to have a checksum), and faking the
PCIR data when loading from OF.
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/subdev/bios/priv.h

@@ -8,7 +8,10 @@ struct nvbios_source {
 	void *(*init)(struct nvkm_bios *, const char *);
 	void  (*fini)(void *);
 	u32   (*read)(void *, u32 offset, u32 length, struct nvkm_bios *);
+	u32   (*size)(void *);
 	bool rw;
+	bool ignore_checksum;
+	bool no_pcir;
 };
 
 int nvbios_extend(struct nvkm_bios *, u32 length);

drivers/gpu/drm/nouveau/nvkm/subdev/bios/shadow.c

@@ -45,7 +45,7 @@ shadow_fetch(struct nvkm_bios *bios, struct shadow *mthd, u32 upto)
 		u32 read = mthd->func->read(data, start, limit - start, bios);
 		bios->size = start + read;
 	}
-	return bios->size >= limit;
+	return bios->size >= upto;
 }
 
 static int
@@ -55,8 +55,15 @@ shadow_image(struct nvkm_bios *bios, int idx, u32 offset, struct shadow *mthd)
 	struct nvbios_image image;
 	int score = 1;
 
+	if (mthd->func->no_pcir) {
+		image.base = 0;
+		image.type = 0;
+		image.size = mthd->func->size(mthd->data);
+		image.last = 1;
+	} else {
 		if (!shadow_fetch(bios, mthd, offset + 0x1000)) {
-		nvkm_debug(subdev, "%08x: header fetch failed\n", offset);
+			nvkm_debug(subdev, "%08x: header fetch failed\n",
+				   offset);
 			return 0;
 		}
 
@@ -64,6 +71,7 @@ shadow_image(struct nvkm_bios *bios, int idx, u32 offset, struct shadow *mthd)
 			nvkm_debug(subdev, "image %d invalid\n", idx);
 			return 0;
 		}
+	}
 	nvkm_debug(subdev, "%08x: type %02x, %d bytes\n",
 		   image.base, image.type, image.size);
 
@@ -74,7 +82,8 @@ shadow_image(struct nvkm_bios *bios, int idx, u32 offset, struct shadow *mthd)
 
 	switch (image.type) {
 	case 0x00:
-		if (nvbios_checksum(&bios->data[image.base], image.size)) {
+		if (!mthd->func->ignore_checksum &&
+		    nvbios_checksum(&bios->data[image.base], image.size)) {
 			nvkm_debug(subdev, "%08x: checksum failed\n",
 				   image.base);
 			if (mthd->func->rw)

drivers/gpu/drm/nouveau/nvkm/subdev/bios/shadowof.c

@@ -21,6 +21,7 @@
  *
  */
 #include "priv.h"
+
 #include <core/pci.h>
 
 #if defined(__powerpc__)
@@ -33,17 +34,26 @@ static u32
 of_read(void *data, u32 offset, u32 length, struct nvkm_bios *bios)
 {
 	struct priv *priv = data;
-	if (offset + length <= priv->size) {
+	if (offset < priv->size) {
+		length = min_t(u32, length, priv->size - offset);
 		memcpy_fromio(bios->data + offset, priv->data + offset, length);
 		return length;
 	}
 	return 0;
 }
 
+static u32
+of_size(void *data)
+{
+	struct priv *priv = data;
+	return priv->size;
+}
+
 static void *
 of_init(struct nvkm_bios *bios, const char *name)
 {
-	struct pci_dev *pdev = bios->subdev.device->func->pci(bios->subdev.device)->pdev;
+	struct nvkm_device *device = bios->subdev.device;
+	struct pci_dev *pdev = device->func->pci(device)->pdev;
 	struct device_node *dn;
 	struct priv *priv;
 	if (!(dn = pci_device_to_OF_node(pdev)))
@@ -62,7 +72,10 @@ nvbios_of = {
 	.init = of_init,
 	.fini = (void(*)(void *))kfree,
 	.read = of_read,
+	.size = of_size,
 	.rw = false,
+	.ignore_checksum = true,
+	.no_pcir = true,
 };
 #else
 const struct nvbios_source