[SeaBIOS] [PATCH 05/15] Add framebuffer size detection

[Christian Gmeiner]

It is possible to read out the framebuffer size via msr. The size
information is needed for VESA later.

Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
---
 vgasrc/geodevga.c | 27 +++++++++++++++++++++++++++
 vgasrc/geodevga.h |  1 +
 2 files changed, 28 insertions(+)

diff --git a/vgasrc/geodevga.c b/vgasrc/geodevga.c
index ae606a7..636d55b 100644
--- a/vgasrc/geodevga.c
+++ b/vgasrc/geodevga.c
@@ -106,6 +106,30 @@ static int legacyio_check(void)
     return ret;
 }
 
+static u32 framebuffer_size(void)
+{
+    u32 val;
+    union u64_u32_u msr;
+
+    /* We use the P2D_R0 msr to read out the number of pages.
+     * One page has a size of 4k
+     *
+     * Bit      Name    Description
+     * 39:20    PMAX    Physical Memory Address Max
+     * 19:0     PMIX    Physical Memory Address Min
+     *
+     */
+    msr = geode_msrRead(GLIU0_P2D_RO);
+
+    u32 pmax = ((msr.hi & 0xff) << 12) | ((msr.lo & 0xfff00000) >> 20);
+    u32 pmin = (msr.lo & 0x000fffff);
+    
+    val = pmax - pmin;
+    val += 1;
+
+    /* The page size is 4k */
+    return (val << 12);
+}
 
 /****************************************************************
 * Init Functions
@@ -140,6 +164,9 @@ static int dc_setup(void)
 
     geode_memWrite(dc_base + DC_UNLOCK, 0x0, DC_LOCK_LOCK);
 
+    u32 fb_size = framebuffer_size(); // in byte
+    dprintf(1, "%d KB of video memory at 0x%08x\n", fb_size / 1024, fb);
+    
     return 0;
 }
 
diff --git a/vgasrc/geodevga.h b/vgasrc/geodevga.h
index 7098037..14e33d6 100644
--- a/vgasrc/geodevga.h
+++ b/vgasrc/geodevga.h
@@ -26,6 +26,7 @@
 #define MSR_GLIU0                       (1 << 28)
 #define MSR_GLIU0_BASE4                 (MSR_GLIU0 + 0x23)  /* LX */
 #define GLIU0_P2D_BM_4                  (MSR_GLIU0 + 0x24)  /* GX2 */
+#define GLIU0_P2D_RO			(MSR_GLIU0 + 0x29)
 #define GLIU0_IOD_BM_0                  (MSR_GLIU0 + 0xE0)
 #define GLIU0_IOD_BM_1                  (MSR_GLIU0 + 0xE1)
 #define DC_SPARE                        0x80000011
-- 
1.7.11.rc2.5.g68f532f