[PATCH v3 2/2] serial: 8250_dw: add Ambarella CV75 quirks

[Long Zhao via B4 Relay <devnull+longzhao.ambarella.com@kernel.org>]

From: Long Zhao <longzhao@ambarella.com>

Add CV75 platform data with an ETOI IER mask and skip-set-rate so the
DesignWare 8250 driver can drive the Ambarella UART for console use.

Signed-off-by: Long Zhao <longzhao@ambarella.com>
---
 drivers/tty/serial/8250/8250_dw.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 5fba913f3301..e8aa592924d4 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -43,6 +43,9 @@
 #define RZN1_UART_xDMACR_8_WORD_BURST	(2 << 1)
 #define RZN1_UART_xDMACR_BLK_SZ(x)	((x) << 3)
 
+/* Ambarella specific register fields */
+#define AMBARELLA_UART_IER_ETOI		BIT(5)
+
 /* Quirks */
 #define DW_UART_QUIRK_OCTEON		BIT(0)
 #define DW_UART_QUIRK_ARMADA_38X	BIT(1)
@@ -60,6 +63,7 @@
 
 struct dw8250_platform_data {
 	u8 usr_reg;
+	u8 ier_mask;
 	u32 cpr_value;
 	unsigned int quirks;
 };
@@ -572,6 +576,23 @@ static void dw8250_prepare_rx_dma(struct uart_8250_port *p)
 	dw8250_writel_ext(up, RZN1_UART_RDMACR, val);
 }
 
+static int dw8250_ier_mask_startup(struct uart_port *p)
+{
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
+	struct uart_8250_port *up = up_to_u8250p(p);
+	int ret;
+
+	ret = serial8250_do_startup(p);
+	if (ret)
+		return ret;
+
+	/* Keep variant-specific bits in the shadow across subsequent updates. */
+	up->ier |= d->pdata->ier_mask;
+	serial_port_out(p, UART_IER, up->ier);
+
+	return 0;
+}
+
 static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 {
 	unsigned int quirks = data->pdata->quirks;
@@ -606,6 +627,8 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 		p->serial_in = dw8250_serial_in32;
 		data->uart_16550_compatible = true;
 	}
+	if (data->pdata->ier_mask)
+		p->startup = dw8250_ier_mask_startup;
 }
 
 static void dw8250_reset_control_assert(void *data)
@@ -879,6 +902,12 @@ static const struct dw8250_platform_data dw8250_intc10ee = {
 	.quirks = DW_UART_QUIRK_IER_KICK,
 };
 
+static const struct dw8250_platform_data dw8250_ambarella_cv75_data = {
+	.usr_reg = DW_UART_USR,
+	.ier_mask = AMBARELLA_UART_IER_ETOI,
+	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
+};
+
 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) |
@@ -889,6 +918,7 @@ static const struct dw8250_platform_data dw8250_ultrarisc_dp1000_data = {
 };
 
 static const struct of_device_id dw8250_of_match[] = {
+	{ .compatible = "ambarella,cv75-uart", .data = &dw8250_ambarella_cv75_data },
 	{ .compatible = "snps,dw-apb-uart", .data = &dw8250_dw_apb },
 	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
 	{ .compatible = "marvell,armada-38x-uart", .data = &dw8250_armada_38x_data },

-- 
2.34.1