[PATCH] scx200_acb: Fix for negack clear errata
From: Jordan Crouse <[email protected]>
This patch is a fix for the CS5535 errata 111:
When the SMB controller tries to access a non-existing device, it sets
the NEGACK bit, SMB I/O Offset 01h[4], to 1 after it detects no
acknowledge at the ninth clock. The specification says there are only
two ways to clear this status bit: write 1 to this bit or disable the
SMB controller. Sometimes this bit is cleared by a read of this
register, but not always.
Signed-off-by: Jordan Crouse <[email protected]>
---
drivers/i2c/busses/scx200_acb.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/scx200_acb.c b/drivers/i2c/busses/scx200_acb.c
index 8bd305e..e7a2225 100644
--- a/drivers/i2c/busses/scx200_acb.c
+++ b/drivers/i2c/busses/scx200_acb.c
@@ -133,6 +133,9 @@ static void scx200_acb_machine(struct sc
outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
outb(ACBST_STASTR | ACBST_NEGACK, ACBST);
+
+ /* Reset the status register */
+ outb(0, ACBST);
return;
}
@@ -228,6 +231,10 @@ static void scx200_acb_poll(struct scx20
timeout = jiffies + POLL_TIMEOUT;
while (time_before(jiffies, timeout)) {
status = inb(ACBST);
+
+ /* Reset the status register to avoid the hang */
+ outb(0, ACBST);
+
if ((status & (ACBST_SDAST|ACBST_BER|ACBST_NEGACK)) != 0) {
scx200_acb_machine(iface, status);
return;