Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1733310bb762cb926669f2c10f6f8719bb20ed91
Commit: 1733310bb762cb926669f2c10f6f8719bb20ed91
Parent: abb4a2390737867353ebafc012d45f2b03f3f944
Author: Dave Jiang <[EMAIL PROTECTED]>
AuthorDate: Sun May 6 14:48:50 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon May 7 12:12:50 2007 -0700
MPSC serial driver tx locking
The MPSC serial driver assumes that interrupt is always on to pick up the
DMA transmit ops that aren't submitted while the DMA engine is active.
However when irqs are off for a period of time such as operations under
kernel crash dump console messages do not show up due to additional DMA ops
are being dropped. This makes console writes to process through all the tx
DMAs queued up before submitting a new request.
Also, the current locking mechanism does not protect the hardware registers
and ring buffer when a printk is done during the serial write operations.
The additional per port transmit lock provides a finer granular locking and
protects registers being clobbered while printks are nested within UART
writes.
Signed-off-by: Dave Jiang <[EMAIL PROTECTED]>
Signed-off-by: Mark A. Greer <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
drivers/serial/mpsc.c | 25 ++++++++++++++++++++++++-
1 files changed, 24 insertions(+), 1 deletions(-)
diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c
index 3d2fcc5..d09f209 100644
--- a/drivers/serial/mpsc.c
+++ b/drivers/serial/mpsc.c
@@ -183,6 +183,7 @@ struct mpsc_port_info {
u8 *txb_p; /* Phys addr of txb */
int txr_head; /* Where new data goes */
int txr_tail; /* Where sent data comes off */
+ spinlock_t tx_lock; /* transmit lock */
/* Mirrored values of regs we can't read (if 'mirror_regs' set) */
u32 MPSC_MPCR_m;
@@ -1212,6 +1213,9 @@ mpsc_tx_intr(struct mpsc_port_info *pi)
{
struct mpsc_tx_desc *txre;
int rc = 0;
+ unsigned long iflags;
+
+ spin_lock_irqsave(&pi->tx_lock, iflags);
if (!mpsc_sdma_tx_active(pi)) {
txre = (struct mpsc_tx_desc *)(pi->txr +
@@ -1248,6 +1252,7 @@ mpsc_tx_intr(struct mpsc_port_info *pi)
mpsc_sdma_start_tx(pi); /* start next desc if ready */
}
+ spin_unlock_irqrestore(&pi->tx_lock, iflags);
return rc;
}
@@ -1338,11 +1343,16 @@ static void
mpsc_start_tx(struct uart_port *port)
{
struct mpsc_port_info *pi = (struct mpsc_port_info *)port;
+ unsigned long iflags;
+
+ spin_lock_irqsave(&pi->tx_lock, iflags);
mpsc_unfreeze(pi);
mpsc_copy_tx_data(pi);
mpsc_sdma_start_tx(pi);
+ spin_unlock_irqrestore(&pi->tx_lock, iflags);
+
pr_debug("mpsc_start_tx[%d]\n", port->line);
return;
}
@@ -1625,6 +1635,16 @@ mpsc_console_write(struct console *co, const char *s,
uint count)
struct mpsc_port_info *pi = &mpsc_ports[co->index];
u8 *bp, *dp, add_cr = 0;
int i;
+ unsigned long iflags;
+
+ spin_lock_irqsave(&pi->tx_lock, iflags);
+
+ while (pi->txr_head != pi->txr_tail) {
+ while (mpsc_sdma_tx_active(pi))
+ udelay(100);
+ mpsc_sdma_intr_ack(pi);
+ mpsc_tx_intr(pi);
+ }
while (mpsc_sdma_tx_active(pi))
udelay(100);
@@ -1668,6 +1688,7 @@ mpsc_console_write(struct console *co, const char *s,
uint count)
pi->txr_tail = (pi->txr_tail + 1) & (MPSC_TXR_ENTRIES - 1);
}
+ spin_unlock_irqrestore(&pi->tx_lock, iflags);
return;
}
@@ -2005,7 +2026,8 @@ mpsc_drv_probe(struct platform_device *dev)
if (!(rc = mpsc_drv_map_regs(pi, dev))) {
mpsc_drv_get_platform_data(pi, dev, dev->id);
- if (!(rc = mpsc_make_ready(pi)))
+ if (!(rc = mpsc_make_ready(pi))) {
+ spin_lock_init(&pi->tx_lock);
if (!(rc = uart_add_one_port(&mpsc_reg,
&pi->port)))
rc = 0;
@@ -2014,6 +2036,7 @@ mpsc_drv_probe(struct platform_device *dev)
(struct uart_port *)pi);
mpsc_drv_unmap_regs(pi);
}
+ }
else
mpsc_drv_unmap_regs(pi);
}
-
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
