serial: 8250_em: Use pseudo offset for UART_FCR

UART_FCR shares the same offset with UART_IIR. We cannot use UART_FCR
in serial8250_em_serial_in() as it overlaps with UART_IIR.

Define UART_FCR_EM macro with a high value to avoid overlapping
with existing UART_* register defines and define another macro
UART_FCR_EM_HW for the real offset.

Use these macros in serial8250_em_serial{_in/_out} function to
read/write FCR register.

Suggested-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230227114152.22265-7-biju.das.jz@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_em.c b/drivers/tty/serial/8250/8250_em.c
index dcf1761..7614ced 100644 (file)
--- a/drivers/tty/serial/8250/8250_em.c
+++ b/drivers/tty/serial/8250/8250_em.c
@@ -19,6 +19,13 @@
 #define UART_DLL_EM 9
 #define UART_DLM_EM 10
 
+/*
+ * A high value for UART_FCR_EM avoids overlapping with existing UART_*
+ * register defines. UART_FCR_EM_HW is the real HW register offset.
+ */
+#define UART_FCR_EM 0x10003
+#define UART_FCR_EM_HW 3
+
 struct serial8250_em_priv {
        int line;
 };
@@ -29,12 +36,15 @@ static void serial8250_em_serial_out(struct uart_port *p, int offset, int value)
        case UART_TX: /* TX @ 0x00 */
                writeb(value, p->membase);
                break;
-       case UART_FCR: /* FCR @ 0x0c (+1) */
        case UART_LCR: /* LCR @ 0x10 (+1) */
        case UART_MCR: /* MCR @ 0x14 (+1) */
        case UART_SCR: /* SCR @ 0x20 (+1) */
                writel(value, p->membase + ((offset + 1) << 2));
                break;
+       case UART_FCR:
+       case UART_FCR_EM:
+               writel(value, p->membase + (UART_FCR_EM_HW << 2));
+               break;
        case UART_IER: /* IER @ 0x04 */
                value &= 0x0f; /* only 4 valid bits - not Xscale */
                fallthrough;
@@ -55,6 +65,8 @@ static unsigned int serial8250_em_serial_in(struct uart_port *p, int offset)
        case UART_MSR: /* MSR @ 0x1c (+1) */
        case UART_SCR: /* SCR @ 0x20 (+1) */
                return readl(p->membase + ((offset + 1) << 2));
+       case UART_FCR_EM:
+               return readl(p->membase + (UART_FCR_EM_HW << 2));
        case UART_IER: /* IER @ 0x04 */
        case UART_IIR: /* IIR @ 0x08 */
        case UART_DLL_EM: /* DLL @ 0x24 (+9) */