drm/nouveau/bios: cache ramcfg strap on later chipsets

This fixes suspend/resume on at least Quadro 400.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/drivers/gpu/drm/nouveau/core/include/subdev/bios/init.h b/drivers/gpu/drm/nouveau/core/include/subdev/bios/init.h
index e69a8bdc6e97..ca2f6bf37f46 100644
--- a/drivers/gpu/drm/nouveau/core/include/subdev/bios/init.h
+++ b/drivers/gpu/drm/nouveau/core/include/subdev/bios/init.h
@@ -13,6 +13,7 @@ struct nvbios_init {
         u32 nested;
         u16 repeat;
         u16 repend;
+        u32 ramcfg;
 };
 
 int nvbios_exec(struct nvbios_init *);
diff --git a/drivers/gpu/drm/nouveau/core/subdev/bios/init.c b/drivers/gpu/drm/nouveau/core/subdev/bios/init.c
index 98f78cf318b0..2917d552689b 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/bios/init.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/bios/init.c
@@ -411,9 +411,25 @@ init_ram_restrict_group_count(struct nvbios_init *init)
 }
 
 static u8
+init_ram_restrict_strap(struct nvbios_init *init)
+{
+        /* This appears to be the behaviour of the VBIOS parser, and *is*
+         * important to cache the NV_PEXTDEV_BOOT0 on later chipsets to
+         * avoid fucking up the memory controller (somehow) by reading it
+         * on every INIT_RAM_RESTRICT_ZM_GROUP opcode.
+         *
+         * Preserving the non-caching behaviour on earlier chipsets just
+         * in case *not* re-reading the strap causes similar breakage.
+         */
+        if (!init->ramcfg || init->bios->version.major < 0x70)
+                init->ramcfg = init_rd32(init, 0x101000);
+        return (init->ramcfg & 0x00000003c) >> 2;
+}
+
+static u8
 init_ram_restrict(struct nvbios_init *init)
 {
-        u32 strap = (init_rd32(init, 0x101000) & 0x0000003c) >> 2;
+        u8  strap = init_ram_restrict_strap(init);
         u16 table = init_ram_restrict_table(init);
         if (table)
                 return nv_ro08(init->bios, table + strap);