On Fri, 17 Feb 2023, Biju Das wrote:
> 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.
>
> This patch introduces a macro UART_FCR_EM with a high value to
> avoid overlapping with existing UART_* register defines.
>
> This will help us to use UART_FCR_EM consistently in serial8250_em_
> serial{_in/_out} function to read/write FCR register.
>
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> Suggested-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> ---
> v4:
> * New patch. Used UART_FCR_EM for read/write of FCR register.
> ---
> drivers/tty/serial/8250/8250_em.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/8250/8250_em.c b/drivers/tty/serial/8250/8250_em.c
> index 499d7a8847ec..4165fd3bb17a 100644
> --- 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 +36,14 @@ 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) */
8250_port wants this to remain in place, I think. Otherwise it's attempts
to set UART_FCR will end up into wrong destination.
--
i.
> 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_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;
> @@ -54,6 +63,8 @@ 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) */
>
