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| author |   Dan Williams <dan.j.williams@intel.com> | 2012-04-06 11:49:50 -0700 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-04-09 10:38:30 -0700 |
| commit | bc02d15a3452fdf9276e8fb89c5e504a88df888a (patch) | |
| tree | b7014c75d121418b0bc88d8c74f699f9a59adc24 /drivers/tty/serial/8250/8250.c | |
| parent | Revert "serial/8250_pci: setup-quirk workaround for the kt serial controller" (diff) | |
| download | linux-dev-bc02d15a3452fdf9276e8fb89c5e504a88df888a.tar.xz linux-dev-bc02d15a3452fdf9276e8fb89c5e504a88df888a.zip | |
serial/8250_pci: add a "force background timer" flag and use it for the "kt" serial port
Workaround dropped notifications in the iir register. Register reads
coincident with new interrupt notifications sometimes result in this
device clearing the interrupt event without reporting it in the read
data.
The serial core already has a heuristic for determining when a device
has an untrustworthy iir register. In this case when we apriori know
that the iir is faulty use a flag (UPF_BUG_THRE) to bypass the test and
force usage of the background timer.
[stable: 3.3.x]
Acked-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: Nhan H Mai <nhan.h.mai@intel.com>
Reported-by: Sudhakar Mamillapalli <sudhakar@fb.com>
Tested-by: Nhan H Mai <nhan.h.mai@intel.com>
Tested-by: Sudhakar Mamillapalli <sudhakar@fb.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/8250/8250.c')
| -rw-r--r-- | drivers/tty/serial/8250/8250.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c index 56492d208a7a..5c27f7e6c9f1 100644 --- a/drivers/tty/serial/8250/8250.c +++ b/drivers/tty/serial/8250/8250.c @@ -2035,10 +2035,12 @@ static int serial8250_startup(struct uart_port *port) spin_unlock_irqrestore(&port->lock, flags); /* - * If the interrupt is not reasserted, setup a timer to - * kick the UART on a regular basis. + * If the interrupt is not reasserted, or we otherwise + * don't trust the iir, setup a timer to kick the UART + * on a regular basis. */ - if (!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) { + if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) || + up->port.flags & UPF_BUG_THRE) { up->bugs |= UART_BUG_THRE; pr_debug("ttyS%d - using backup timer\n", serial_index(port)); |