[PATCH 2/2] serial: 8250_dw: Add ti,tda54-uart quirk to skip empty FIFO read

[Moteen Shah]

dw8250_handle_irq() does a bogus RX read on RX_TIMEOUT with no data
present, to avoid an interrupt storm. On the IP version used in
TDA54, that interrupt storm no longer occurs, but reading an empty
FIFO instead triggers a data abort.

Add a DW_UART_QUIRK_SKIP_RX_TIMEOUT_READ quirk for ti,tda54-uart to
skip that read and avoid the data abort.

Signed-off-by: Udit Kumar <u-kumar1@xxxxxx>
Signed-off-by: Moteen Shah <m-shah@xxxxxx>
---
 drivers/tty/serial/8250/8250_dw.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 5fba913f3301..a1ce00156ae2 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -51,6 +51,7 @@
 #define DW_UART_QUIRK_APMC0D08		BIT(4)
 #define DW_UART_QUIRK_CPR_VALUE		BIT(5)
 #define DW_UART_QUIRK_IER_KICK		BIT(6)
+#define DW_UART_QUIRK_SKIP_RX_TIMEOUT_READ	BIT(7)
 
 /*
  * Number of consecutive IIR_NO_INT interrupts required to trigger interrupt
@@ -436,7 +437,7 @@ static int dw8250_handle_irq(struct uart_port *p)
 	 * This problem has only been observed so far when not in DMA mode
 	 * so we limit the workaround only to non-DMA mode.
 	 */
-	if (!up->dma && rx_timeout) {
+	if (!(quirks & DW_UART_QUIRK_SKIP_RX_TIMEOUT_READ) && !up->dma && rx_timeout) {
 		status = serial_lsr_in(up);
 
 		if (!(status & (UART_LSR_DR | UART_LSR_BI)))
@@ -888,6 +889,11 @@ static const struct dw8250_platform_data dw8250_ultrarisc_dp1000_data = {
 	.quirks = DW_UART_QUIRK_CPR_VALUE,
 };
 
+static const struct dw8250_platform_data dw8250_tda54 = {
+	.usr_reg = DW_UART_USR,
+	.quirks = DW_UART_QUIRK_SKIP_RX_TIMEOUT_READ,
+};
+
 static const struct of_device_id dw8250_of_match[] = {
 	{ .compatible = "snps,dw-apb-uart", .data = &dw8250_dw_apb },
 	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
@@ -895,6 +901,7 @@ static const struct of_device_id dw8250_of_match[] = {
 	{ .compatible = "renesas,rzn1-uart", .data = &dw8250_renesas_rzn1_data },
 	{ .compatible = "sophgo,sg2044-uart", .data = &dw8250_skip_set_rate_data },
 	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
+	{ .compatible = "ti,tda54-uart", .data = &dw8250_tda54 },
 	{ .compatible = "ultrarisc,dp1000-uart", .data = &dw8250_ultrarisc_dp1000_data },
 	{ /* Sentinel */ }
 };
-- 
2.34.1