Re: [PATCH v5 10/12] serial: 8250: add Ambarella UART driver

On Tue, Aug 18, 2026 at 06:31:24PM +0800, Long Zhao via B4 Relay wrote:

Add an 8250 platform driver for Ambarella CV75 instead of claiming
snps,dw-apb-uart compatibility.

This is a record from a changelog. There is nothing in the commit message.
...

The code seems like an almost blind copy of 8250_dw.c.

+#define AMBARELLA_UART_USR		0x1f
+#define AMBARELLA_UART_USR_BUSY		BIT(0)

So, is it Synopsys IP-based design? How this gets into this platform? This
whole story completely made me lost.

+#define AMBARELLA_UART_IIR_IID		GENMASK(3, 0)
+#define AMBARELLA_UART_IIR_STATUS	GENMASK(5, 0)

...

+	of_property_read_u32(dev->of_node, "reg-shift", &reg_shift);
+	of_property_read_u32(dev->of_node, "reg-io-width", &reg_io_width);
+	uart.port.regshift = reg_shift;

+	switch (reg_io_width) {
+	case 4:
+		uart.port.iotype = UPIO_MEM32;
+		uart.port.serial_in = ambarella_serial_in;
+		uart.port.serial_out = ambarella_serial_out;
+		break;
+	default:
+		return dev_err_probe(dev, -EINVAL,
+				     "unsupported reg-io-width %u\n",
+				     reg_io_width);
+	}

This is handled by uart_read_port_properties().

-- 
With Best Regards,
Andy Shevchenko