scx200_acb: Add a module option to tune the SMB_CLK

[Jordan Crouse]

Commit:     56d79bae58f728a1a7211ce295fdbc28b1548547
Parent:     56340040bf66343f6e34ab86bceda2b46470fae7
commit 56d79bae58f728a1a7211ce295fdbc28b1548547
Author:     Jordan Crouse <jordan.crouse at amd.com>
AuthorDate: Thu Nov 2 13:23:27 2006 +0800
Commit:     David Woodhouse <dwmw2 at infradead.org>
CommitDate: Thu Nov 2 13:23:27 2006 +0800

    scx200_acb: Add a module option to tune the SMB_CLK
    
    Add a module option to change the SMB_CLK period.  Some platforms
    need to be able to tune this value for better performance.
    
    Signed-off-by: David Woodhouse <dwmw2 at infradead.org>
---
 drivers/i2c/busses/scx200_acb.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/scx200_acb.c b/drivers/i2c/busses/scx200_acb.c
index 32aab0d..b4848eb 100644
--- a/drivers/i2c/busses/scx200_acb.c
+++ b/drivers/i2c/busses/scx200_acb.c
@@ -47,6 +47,10 @@ static int base[MAX_DEVICES] = { 0x820, 
 module_param_array(base, int, NULL, 0);
 MODULE_PARM_DESC(base, "Base addresses for the ACCESS.bus controllers");
 
+static unsigned int smbclk = 0x70;
+module_param(smbclk, uint, 0);
+MODULE_PARM_DESC(smbclk, "Specify the SMB_CLK value");
+
 #define POLL_TIMEOUT	(HZ/5)
 
 enum scx200_acb_state {
@@ -109,6 +113,7 @@ #define    ACBCTL1_START	0x01
 #define ACBADDR		(iface->base + 4)
 #define ACBCTL2		(iface->base + 5)
 #define    ACBCTL2_ENABLE	0x01
+#define ACBCTL3        (iface->base + 6)
 
 /************************************************************************/
 
@@ -395,11 +400,13 @@ static __init int scx200_acb_probe(struc
 {
 	u8 val;
 
-	/* Disable the ACCESS.bus device and Configure the SCL
-	   frequency: 16 clock cycles */
-	outb(0x70, ACBCTL2);
+	/* Disable the ACCESS.bus device and Configure the SCL */
+
+	outb((smbclk & 0x7F) << 1, ACBCTL2);
+
+	outb((smbclk >> 7) & 0xFF, ACBCTL3);
 
-	if (inb(ACBCTL2) != 0x70) {
+	if (inb(ACBCTL2) != ((smbclk & 0x7F) << 1)) {
 		pr_debug(NAME ": ACBCTL2 readback failed\n");
 		return -ENXIO;
 	}