[PATCH v5 4/4] serial: 8250_dw: Use a fixed CPR value for UltraRISC DP1000 UART

Jia Wang wangjia at ultrarisc.com
Mon Apr 27 22:26:29 PDT 2026


The UltraRISC DP1000 UART does not provide the standard CPR register used
by 8250_dw to discover port capabilities.

Provide a fixed CPR value for the DP1000-specific compatible so the
driver can configure the port correctly.

Signed-off-by: Jia Wang <wangjia at ultrarisc.com>
---
 drivers/tty/serial/8250/8250_dw.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 5cf3bb74b285..6fa7c8440919 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -960,6 +960,16 @@ static const struct dw8250_platform_data dw8250_intc10ee = {
 	.quirks = DW_UART_QUIRK_IER_KICK,
 };
 
+static const struct dw8250_platform_data dw8250_ultrarisc_dp1000_data = {
+	.usr_reg = DW_UART_USR,
+	.cpr_value = FIELD_PREP_CONST(DW_UART_CPR_ABP_DATA_WIDTH, 2) |
+		     DW_UART_CPR_THRE_MODE |
+		     DW_UART_CPR_DMA_EXTRA |
+		     FIELD_PREP_CONST(DW_UART_CPR_FIFO_MODE,
+				      DW_UART_CPR_FIFO_MODE_FROM_SIZE(32)),
+	.quirks = DW_UART_QUIRK_CPR_VALUE,
+};
+
 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 },
@@ -967,6 +977,7 @@ 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 = "ultrarisc,dp1000-uart", .data = &dw8250_ultrarisc_dp1000_data },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, dw8250_of_match);

-- 
2.34.1




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