[PATCH 2/3] gxfb/lxfb: detect framebuffer size using an MSR if VSA2 isn't available

[Andres Salomon <dilinger@queued.net>]

If there's no VSA2 (ie, if we're using tinybios or OpenFirmware), use
the GLIU's P2D Range Offset Descriptor to determine how much memory we
have available for the framebuffer.

Originally based on a patch by Jordan Crouse.  Tested with OpenFirmware;
Pascal informs me that tinybios has a stub that fills in P2D_RO0.

Signed-off-by: Andres Salomon <dilinger@debian.org>
---
 drivers/video/geode/display_gx.c |   18 +++++++++++++++++-
 drivers/video/geode/lxfb_ops.c   |   16 ++++++++++++++++
 include/asm-x86/geode.h          |    2 ++
 3 files changed, 35 insertions(+), 1 deletions(-)

diff --git a/drivers/video/geode/display_gx.c b/drivers/video/geode/display_gx.c
index 1e82ecc..e759895 100644
--- a/drivers/video/geode/display_gx.c
+++ b/drivers/video/geode/display_gx.c
@@ -25,7 +25,23 @@ unsigned int gx_frame_buffer_size(void)
 {
 	unsigned int val;
 
-	/* FB size is reported by a virtual register */
+	if (!geode_has_vsa2()) {
+		uint32_t hi, lo;
+
+		/* The number of pages is (PMAX - PMIN)+1 */
+		rdmsr(MSR_GLIU_P2D_RO0, lo, hi);
+
+		/* PMAX */
+		val = ((hi & 0xff) << 12) | ((lo & 0xfff00000) >> 20);
+		/* PMIN */
+		val -= (lo & 0x000fffff);
+		val += 1;
+
+		/* The page size is 4k */
+		return (val << 12);
+	}
+
+	/* FB size can be obtained from the VSA II */
 	/* Virtual register class = 0x02 */
 	/* VG_MEM_SIZE(512Kb units) = 0x00 */
 
diff --git a/drivers/video/geode/lxfb_ops.c b/drivers/video/geode/lxfb_ops.c
index 51080db..becf285 100644
--- a/drivers/video/geode/lxfb_ops.c
+++ b/drivers/video/geode/lxfb_ops.c
@@ -279,6 +279,22 @@ unsigned int lx_framebuffer_size(void)
 {
 	unsigned int val;
 
+	if (!geode_has_vsa2()) {
+		uint32_t hi, lo;
+
+		/* The number of pages is (PMAX - PMIN)+1 */
+		rdmsr(MSR_GLIU_P2D_RO0, lo, hi);
+
+		/* PMAX */
+		val = ((hi & 0xff) << 12) | ((lo & 0xfff00000) >> 20);
+		/* PMIN */
+		val -= (lo & 0x000fffff);
+		val += 1;
+
+		/* The page size is 4k */
+		return (val << 12);
+	}
+
 	/* The frame buffer size is reported by a VSM in VSA II */
 	/* Virtual Register Class    = 0x02                     */
 	/* VG_MEM_SIZE (1MB units)   = 0x00                     */
diff --git a/include/asm-x86/geode.h b/include/asm-x86/geode.h
index 6c8a2a0..d5cc7bf 100644
--- a/include/asm-x86/geode.h
+++ b/include/asm-x86/geode.h
@@ -30,6 +30,8 @@ extern int geode_get_dev_base(unsigned int dev);
 
 /* MSRS */
 
+#define MSR_GLIU_P2D_RO0	0x10000029
+
 #define MSR_LX_GLD_MSR_CONFIG	0x48002001
 #define MSR_LX_MSR_PADSEL	0x48002011	/* NOT 0x48000011; the data
 						 * sheet has the wrong value */
-- 
1.5.4.4



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