[v2] hw/char: Improve RX FIFO depth uses

[PATCH v2 8/9] hw/char/mcf_uart: Really use RX FIFO depth

Posted by Philippe Mathieu-Daudé 2 days, 20 hours ago

While we model a 4-elements RX FIFO since the MCF UART model
was introduced in commit 20dcee94833 ("MCF5208 emulation"),
we only read 1 char at a time!

Have the IOCanReadHandler handler return how many elements are
available, and use that in the IOReadHandler handler.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Luc Michel <luc.michel@amd.com>
---
 hw/char/mcf_uart.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/char/mcf_uart.c b/hw/char/mcf_uart.c
index 95f269ee9b7..529c26be93a 100644
--- a/hw/char/mcf_uart.c
+++ b/hw/char/mcf_uart.c
@@ -281,14 +281,16 @@ static int mcf_uart_can_receive(void *opaque)
 {
     mcf_uart_state *s = (mcf_uart_state *)opaque;
 
-    return s->rx_enabled && (s->sr & MCF_UART_FFULL) == 0;
+    return s->rx_enabled ? FIFO_DEPTH - s->fifo_len : 0;
 }
 
 static void mcf_uart_receive(void *opaque, const uint8_t *buf, int size)
 {
     mcf_uart_state *s = (mcf_uart_state *)opaque;
 
-    mcf_uart_push_byte(s, buf[0]);
+    for (int i = 0; i < size; i++) {
+        mcf_uart_push_byte(s, buf[i]);
+    }
 }
 
 static const MemoryRegionOps mcf_uart_ops = {
-- 
2.47.1

Re: [PATCH v2 8/9] hw/char/mcf_uart: Really use RX FIFO depth

Posted by Thomas Huth 19 hours ago

Am Thu, 20 Feb 2025 10:29:01 +0100
schrieb Philippe Mathieu-Daudé <philmd@linaro.org>:

> While we model a 4-elements RX FIFO since the MCF UART model
> was introduced in commit 20dcee94833 ("MCF5208 emulation"),
> we only read 1 char at a time!
> 
> Have the IOCanReadHandler handler return how many elements are
> available, and use that in the IOReadHandler handler.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Luc Michel <luc.michel@amd.com>
> ---
>  hw/char/mcf_uart.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/char/mcf_uart.c b/hw/char/mcf_uart.c
> index 95f269ee9b7..529c26be93a 100644
> --- a/hw/char/mcf_uart.c
> +++ b/hw/char/mcf_uart.c
> @@ -281,14 +281,16 @@ static int mcf_uart_can_receive(void *opaque)
>  {
>      mcf_uart_state *s = (mcf_uart_state *)opaque;
>  
> -    return s->rx_enabled && (s->sr & MCF_UART_FFULL) == 0;
> +    return s->rx_enabled ? FIFO_DEPTH - s->fifo_len : 0;
>  }
>  
>  static void mcf_uart_receive(void *opaque, const uint8_t *buf, int size)
>  {
>      mcf_uart_state *s = (mcf_uart_state *)opaque;
>  
> -    mcf_uart_push_byte(s, buf[0]);
> +    for (int i = 0; i < size; i++) {
> +        mcf_uart_push_byte(s, buf[i]);
> +    }
>  }

Tested-by: Thomas Huth <huth@tuxfamily.org>
Reviewed-by: Thomas Huth <huth@tuxfamily.org>