[MTD] MAPS: Add parameter to amd76xrom to override rom window size

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Commit:     c9073ce02adfa273a3d6d53eac8c4c035510ad9c
Parent:     1ef93a0f668c8736cb6b6c3a43a5b8101efa24af
commit c9073ce02adfa273a3d6d53eac8c4c035510ad9c
Author:     Ryan Jackson <rjackson at lnxi.com>
AuthorDate: Fri Oct 20 14:41:01 2006 -0700
Commit:     David Woodhouse <dwmw2 at infradead.org>
CommitDate: Sat Oct 21 16:15:43 2006 +0100

    [MTD] MAPS: Add parameter to amd76xrom to override rom window size
    
    The 2 bits controlling the window size are often set to allow reading the
    BIOS, but too small to allow writing, since the lock registers are 4MiB
    lower in the address space than the data.  This is intended to prevent
    flashing the bios, perhaps accidentally.
    
    The bits are 6 and 7.  If both bits are set, it is a 5MiB window. If only
    the 7 Bit is set, it is a 4MiB window.  Otherwise, it is a 64KiB window.
    
    This parameter allows the driver to override the BIOS settings.
    
    Signed-off-by: Ryan Jackson <rjackson at lnxi.com>
    Signed-off-by: Andrew Morton <akpm at osdl.org>
    Signed-off-by: David Woodhouse <dwmw2 at infradead.org>
---
 drivers/mtd/maps/amd76xrom.c |   34 ++++++++++++++++++++++++++++------
 1 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/maps/amd76xrom.c b/drivers/mtd/maps/amd76xrom.c
index 797caff..78b6711 100644
--- a/drivers/mtd/maps/amd76xrom.c
+++ b/drivers/mtd/maps/amd76xrom.c
@@ -7,6 +7,7 @@
 
 #include <linux/module.h>
 #include <linux/types.h>
+#include <linux/version.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <asm/io.h>
@@ -44,6 +45,23 @@ struct amd76xrom_map_info {
 	char map_name[sizeof(MOD_NAME) + 2 + ADDRESS_NAME_LEN];
 };
 
+/* The 2 bits controlling the window size are often set to allow reading
+ * the BIOS, but too small to allow writing, since the lock registers are
+ * 4MiB lower in the address space than the data.
+ *
+ * This is intended to prevent flashing the bios, perhaps accidentally.
+ *
+ * This parameter allows the normal driver to over-ride the BIOS settings.
+ *
+ * The bits are 6 and 7.  If both bits are set, it is a 5MiB window.
+ * If only the 7 Bit is set, it is a 4MiB window.  Otherwise, a
+ * 64KiB window.
+ *
+ */
+static uint win_size_bits;
+module_param(win_size_bits, uint, 0);
+MODULE_PARM_DESC(win_size_bits, "ROM window size bits override for 0x43 byte, normally set by BIOS.");
+
 static struct amd76xrom_window amd76xrom_window = {
 	.maps = LIST_HEAD_INIT(amd76xrom_window.maps),
 };
@@ -95,6 +113,16 @@ static int __devinit amd76xrom_init_one 
 	/* Remember the pci dev I find the window in - already have a ref */
 	window->pdev = pdev;
 
+	/* Enable the selected rom window.  This is often incorrectly
+	 * set up by the BIOS, and the 4MiB offset for the lock registers
+	 * requires the full 5MiB of window space.
+	 *
+	 * This 'write, then read' approach leaves the bits for
+	 * other uses of the hardware info.
+	 */
+	pci_read_config_byte(pdev, 0x43, &byte);
+	pci_write_config_byte(pdev, 0x43, byte | win_size_bits );
+
 	/* Assume the rom window is properly setup, and find it's size */
 	pci_read_config_byte(pdev, 0x43, &byte);
 	if ((byte & ((1<<7)|(1<<6))) == ((1<<7)|(1<<6))) {
@@ -129,12 +157,6 @@ static int __devinit amd76xrom_init_one 
 			(unsigned long long)window->rsrc.end);
 	}
 
-#if 0
-
-	/* Enable the selected rom window */
-	pci_read_config_byte(pdev, 0x43, &byte);
-	pci_write_config_byte(pdev, 0x43, byte | rwindow->segen_bits);
-#endif
 
 	/* Enable writes through the rom window */
 	pci_read_config_byte(pdev, 0x40, &byte);