[PATCH] lib: utils/serial: Add PXA UARTs support

[Junhui Liu]

The PXA variant of the uart8250 adds the UART Unit Enable bit (UUE) that
needs to be set to enable the XScale PXA UART. And it is required for
some RISC-V SoCs like the Spacemit K1 that implement the PXA UART.

This introduces the "intel,xscale-uart" compatible to handle setting the
UUE bit.

Signed-off-by: Junhui Liu <junhui.liu at pigmoral.tech>
---
 include/sbi_utils/serial/uart8250.h    |  4 +++-
 lib/utils/serial/fdt_serial_uart8250.c |  7 +++++--
 lib/utils/serial/uart8250.c            | 11 +++++++++--
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/sbi_utils/serial/uart8250.h b/include/sbi_utils/serial/uart8250.h
index d4a8c136a4552c8045a3c83820a35ae2ae86e810..39f4b316ff631159cc81284460fcaf92490be310 100644
--- a/include/sbi_utils/serial/uart8250.h
+++ b/include/sbi_utils/serial/uart8250.h
@@ -12,7 +12,9 @@
 
 #include <sbi/sbi_types.h>
 
+#define UART_CAP_UUE	BIT(0)	/* Check UUE capability for XScale PXA UARTs */
+
 int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
-		  u32 reg_width, u32 reg_offset);
+		  u32 reg_width, u32 reg_offset, u32 capabilities);
 
 #endif
diff --git a/lib/utils/serial/fdt_serial_uart8250.c b/lib/utils/serial/fdt_serial_uart8250.c
index af5ceac924873216a85374b6c937af1b067841d0..02ca92e1ae4659f712559efed4f4399c80f9871e 100644
--- a/lib/utils/serial/fdt_serial_uart8250.c
+++ b/lib/utils/serial/fdt_serial_uart8250.c
@@ -14,8 +14,9 @@
 static int serial_uart8250_init(const void *fdt, int nodeoff,
 				const struct fdt_match *match)
 {
-	int rc;
 	struct platform_uart_data uart = { 0 };
+	ulong capabilities = (ulong)match->data;
+	int rc;
 
 	rc = fdt_parse_uart_node(fdt, nodeoff, &uart);
 	if (rc)
@@ -23,13 +24,15 @@ static int serial_uart8250_init(const void *fdt, int nodeoff,
 
 	return uart8250_init(uart.addr, uart.freq, uart.baud,
 			     uart.reg_shift, uart.reg_io_width,
-			     uart.reg_offset);
+			     uart.reg_offset, capabilities);
 }
 
 static const struct fdt_match serial_uart8250_match[] = {
 	{ .compatible = "ns16550" },
 	{ .compatible = "ns16550a" },
 	{ .compatible = "snps,dw-apb-uart" },
+	{ .compatible = "intel,xscale-uart",
+	  .data = (void *)UART_CAP_UUE },
 	{ },
 };
 
diff --git a/lib/utils/serial/uart8250.c b/lib/utils/serial/uart8250.c
index 1fe053f860e56e7a447259dadb649734ff5016b0..4932fe9f1cc6f5ae196cefa08393eb2f21c8244c 100644
--- a/lib/utils/serial/uart8250.c
+++ b/lib/utils/serial/uart8250.c
@@ -39,6 +39,12 @@
 #define UART_LSR_DR		0x01	/* Receiver data ready */
 #define UART_LSR_BRK_ERROR_BITS	0x1E	/* BI, FE, PE, OE bits */
 
+/* The XScale PXA UARTs define these bits */
+#define UART_IER_DMAE		0x80	/* DMA Requests Enable */
+#define UART_IER_UUE		0x40	/* UART Unit Enable */
+#define UART_IER_NRZE		0x20	/* NRZ coding Enable */
+#define UART_IER_RTOIE		0x10	/* Receiver Time Out Interrupt Enable */
+
 /* clang-format on */
 
 static volatile char *uart8250_base;
@@ -93,7 +99,7 @@ static struct sbi_console_device uart8250_console = {
 };
 
 int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
-		  u32 reg_width, u32 reg_offset)
+		  u32 reg_width, u32 reg_offset, u32 capabilities)
 {
 	u16 bdiv = 0;
 
@@ -109,7 +115,8 @@ int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
 	}
 
 	/* Disable all interrupts */
-	set_reg(UART_IER_OFFSET, 0x00);
+	set_reg(UART_IER_OFFSET, (capabilities & UART_CAP_UUE) ?
+				 UART_IER_UUE : 0x00);
 	/* Enable DLAB */
 	set_reg(UART_LCR_OFFSET, 0x80);
 

---
base-commit: 1ad199124479b9944d5dddc2119e6da9f088f7a7
change-id: 20250223-pxa-uart-support-b9482a6b7297

Best regards,
-- 
Junhui Liu <junhui.liu at pigmoral.tech>