[PATCH v3 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
RX FIFO instead triggers a data abort.

Add a DW_UART_QUIRK_SKIP_EMPTY_FIFO_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 b8a0bca8b536..e7e219611e0b 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_EMPTY_FIFO_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_EMPTY_FIFO_READ) && !up->dma && rx_timeout) {
 		status = serial_lsr_in(up);
 
 		/*
@@ -895,6 +896,11 @@ 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_EMPTY_FIFO_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 },
@@ -902,6 +908,7 @@ 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