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[v5,10/16] hw/char/pl011: Check if receiver is enabled

Message ID 20240719181041.49545-11-philmd@linaro.org
State New
Headers show
Series hw/char/pl011: Implement TX (async) FIFO to avoid blocking the main loop | expand

Commit Message

Philippe Mathieu-Daudé July 19, 2024, 6:10 p.m. UTC 
Do not receive characters when UART or receiver are disabled.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 hw/char/pl011.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Comments

Peter Maydell July 29, 2024, 3:51 p.m. UTC | #1 
On Fri, 19 Jul 2024 at 19:11, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> Do not receive characters when UART or receiver are disabled.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  hw/char/pl011.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/char/pl011.c b/hw/char/pl011.c
> index c76283dccf..0ce91c13d3 100644
> --- a/hw/char/pl011.c
> +++ b/hw/char/pl011.c
> @@ -85,6 +85,7 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
>  #define CR_OUT1     (1 << 12)
>  #define CR_RTS      (1 << 11)
>  #define CR_DTR      (1 << 10)
> +#define CR_RXE      (1 << 9)
>  #define CR_TXE      (1 << 8)
>  #define CR_LBE      (1 << 7)
>  #define CR_UARTEN   (1 << 0)
> @@ -481,9 +482,11 @@ static void pl011_write(void *opaque, hwaddr offset,
>  static int pl011_can_receive(void *opaque)
>  {
>      PL011State *s = (PL011State *)opaque;
> -    int r;
> +    int r = 0;
>
> -    r = s->read_count < pl011_get_fifo_depth(s);
> +    if ((s->cr & CR_UARTEN) && (s->cr & CR_RXE)) {
> +        r = s->read_count < pl011_get_fifo_depth(s);
> +    }
>      trace_pl011_can_receive(s->lcr, s->read_count, r);
>      return r;

I have a vague recollection of a previous conversation
where we discussed whether tightening up the UART-enable
checks would break existing only-tested-on-QEMU baremetal
simple example code. But I can't find it in my email
archive -- do you remember a discussion about this or
am I misremembering?

thanks
-- PMM
diff mbox series

Patch

diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index c76283dccf..0ce91c13d3 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -85,6 +85,7 @@  DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
 #define CR_OUT1     (1 << 12)
 #define CR_RTS      (1 << 11)
 #define CR_DTR      (1 << 10)
+#define CR_RXE      (1 << 9)
 #define CR_TXE      (1 << 8)
 #define CR_LBE      (1 << 7)
 #define CR_UARTEN   (1 << 0)
@@ -481,9 +482,11 @@  static void pl011_write(void *opaque, hwaddr offset,
 static int pl011_can_receive(void *opaque)
 {
     PL011State *s = (PL011State *)opaque;
-    int r;
+    int r = 0;
 
-    r = s->read_count < pl011_get_fifo_depth(s);
+    if ((s->cr & CR_UARTEN) && (s->cr & CR_RXE)) {
+        r = s->read_count < pl011_get_fifo_depth(s);
+    }
     trace_pl011_can_receive(s->lcr, s->read_count, r);
     return r;
 }