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 48dad64389d740a8d30b43a16637ae02b71dfe52..a3eaf293f2048cb18cb53477c63335bf6d6ba85d 100644 (file)
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -637,7 +637,8 @@ 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);