| Message ID | 1391605991-30603-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 86c00b1c..d28d7af 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -2670,6 +2670,10 @@ static void serial8250_config_port(struct uart_port *port, int flags) if (port->type == PORT_16550A && port->iotype == UPIO_AU) up->bugs |= UART_BUG_NOMSR; + /* HW bugs may trigger IRQ while IIR == NO_INT */ + if (port->type == PORT_TEGRA) + up->bugs |= UART_BUG_NOMSR; + if (port->type != PORT_UNKNOWN && flags & UART_CONFIG_IRQ) autoconfig_irq(up);
This is a note to let you know that I have just added a patch titled serial: 8250: enable UART_BUG_NOMSR for Tegra to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 5fc2c6db5506f187d7a9a3618306d6161e51fa74 Mon Sep 17 00:00:00 2001 From: Stephen Warren <swarren@nvidia.com> Date: Tue, 7 Jan 2014 15:00:12 -0700 Subject: serial: 8250: enable UART_BUG_NOMSR for Tegra commit 3685f19e07802ec4207b52465c408f185b66490e upstream. Tegra chips have 4 or 5 identical UART modules embedded. UARTs C..E have their MODEM-control signals tied off to a static state. However UARTs A and B can optionally route those signals to/from package pins, depending on the exact pinmux configuration. When these signals are not routed to package pins, false interrupts may trigger either temporarily, or permanently, all while not showing up in the IIR; it will read as NO_INT. This will eventually lead to the UART IRQ being disabled due to unhandled interrupts. When this happens, the kernel may print e.g.: irq 68: nobody cared (try booting with the "irqpoll" option) In order to prevent this, enable UART_BUG_NOMSR. This prevents UART_IER_MSI from being enabled, which prevents the false interrupts from triggering. In practice, this is not needed under any of the following conditions: * On Tegra chips after Tegra30, since the HW bug has apparently been fixed. * On UARTs C..E since their MODEM control signals are tied to the correct static state which doesn't trigger the issue. * On UARTs A..B if the MODEM control signals are routed out to package pins, since they will then carry valid signals. However, we ignore these exceptions for now, since they are only relevant if a board actually hooks up more than a 4-wire UART, and no currently supported board does this. If we ever support a board that does, we can refine the algorithm that enables UART_BUG_NOMSR to take those exceptions into account, and/or read a flag from DT/... that indicates that the board has hooked up and pinmux'd more than a 4-wire UART. Reported-by: Olof Johansson <olof@lixom.net> # autotester Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/tty/serial/8250/8250_core.c | 4 ++++ 1 file changed, 4 insertions(+) -- 1.8.3.2