serial: 8250_omap: Fix Errata i2310 with RX FIFO level check

commit c128a1b0523b685c8856ddc0ac0e1caef1fdeee5 upstream.

Errata i2310[0] says, Erroneous timeout can be triggered,
if this Erroneous interrupt is not cleared then it may leads
to storm of interrupts.

Commit 9d141c1e6157 ("serial: 8250_omap: Implementation of Errata i2310")
which added the workaround but missed ensuring RX FIFO is really empty
before applying the errata workaround as recommended in the errata text.
Fix this by adding back check for UART_OMAP_RX_LVL to be 0 for
workaround to take effect.

[0] https://www.ti.com/lit/pdf/sprz536 page 23

Fixes: 9d141c1e6157 ("serial: 8250_omap: Implementation of Errata i2310")
Cc: stable@vger.kernel.org
Reported-by: Vignesh Raghavendra <vigneshr@ti.com>
Closes: https://lore.kernel.org/all/e96d0c55-0b12-4cbf-9d23-48963543de49@ti.com/
Signed-off-by: Udit Kumar <u-kumar1@ti.com>
Link: https://lore.kernel.org/r/20240625160725.2102194-1-u-kumar1@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 2bb4514e4956f8a9f90206eadf72b4d330d43b8a..8f472a2080ffa0c5e13554f3b8a6dd60f212ae29 100644 (file)
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -655,7 +655,8 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
         * https://www.ti.com/lit/pdf/sprz536
         */
        if (priv->habit & UART_RX_TIMEOUT_QUIRK &&
-               (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
+           (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
+           serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
                unsigned char efr2, timeout_h, timeout_l;
 
                efr2 = serial_in(up, UART_OMAP_EFR2);