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  3. [PATCH v6 0/7] hw/char/pl011: Implement TX (async) FIFO to avoid blocking the main loop
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[PATCH v6 5/7] hw/char/pl011: Consider TX FIFO overrun error

Philippe Mathieu-Daudé posted 7 patches 1 year ago
There is a newer version of this series
[PATCH v6 5/7] hw/char/pl011: Consider TX FIFO overrun error
Posted by Philippe Mathieu-Daudé 1 year ago 
When transmission is disabled, characters are still queued
to the FIFO which eventually overruns. Report that error
condition in the status register.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/char/pl011.c      | 20 ++++++++++++++++++++
 hw/char/trace-events |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index 447f185e2d5..ef39ab666a2 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -61,6 +61,9 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
 /* Data Register, UARTDR */
 #define DR_BE   (1 << 10)
 
+/* Receive Status Register/Error Clear Register, UARTRSR/UARTECR */
+#define RSR_OE  (1 << 3)
+
 /* Interrupt status bits in UARTRIS, UARTMIS, UARTIMSC */
 #define INT_OE (1 << 10)
 #define INT_BE (1 << 9)
@@ -158,6 +161,16 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)
     return pl011_is_fifo_enabled(s) ? PL011_FIFO_DEPTH : 1;
 }
 
+static bool pl011_is_tx_fifo_full(PL011State *s)
+{
+    if (pl011_is_fifo_enabled(s)) {
+        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
+        return fifo8_is_full(&s->xmit_fifo);
+    }
+    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
+    return !fifo8_is_empty(&s->xmit_fifo);
+}
+
 static inline void pl011_reset_rx_fifo(PL011State *s)
 {
     s->read_count = 0;
@@ -264,6 +277,13 @@ static void pl011_write_txdata(PL011State *s, uint8_t data)
                       "PL011 data written to disabled TX UART\n");
     }
 
+    if (pl011_is_tx_fifo_full(s)) {
+        /* The FIFO is already full. Content remains valid. */
+        trace_pl011_fifo_tx_overrun();
+        s->rsr |= RSR_OE;
+        return;
+    }
+
     trace_pl011_fifo_tx_put(data);
     pl011_loopback_tx(s, data);
     fifo8_push(&s->xmit_fifo, data);
diff --git a/hw/char/trace-events b/hw/char/trace-events
index dd635ac6012..8234f3afa13 100644
--- a/hw/char/trace-events
+++ b/hw/char/trace-events
@@ -67,9 +67,11 @@ pl011_fifo_enable(bool enable) "enable:%u"
 pl011_fifo_is_enabled(bool enabled) "enabled:%u"
 pl011_fifo_rx_put(uint32_t c, int read_count) "new char 0x%02x read_count now %d"
 pl011_fifo_rx_full(void) "RX FIFO now full, RXFF set"
+pl011_fifo_tx_is_full(const char *desc, bool full) "mode:%s full:%u"
 pl011_fifo_tx_put(uint8_t byte) "TX FIFO push char [0x%02x]"
 pl011_fifo_tx_xmit_used(unsigned sent) "TX FIFO used %u chars"
 pl011_fifo_tx_xmit_consumed(unsigned sent) "TX FIFO consumed %u chars"
+pl011_fifo_tx_overrun(void) "TX FIFO overrun"
 pl011_baudrate_change(unsigned int baudrate, uint64_t clock, uint32_t ibrd, uint32_t fbrd) "new baudrate %u (clk: %" PRIu64 "hz, ibrd: %" PRIu32 ", fbrd: %" PRIu32 ")"
 
 # cmsdk-apb-uart.c
-- 
2.47.1
Re: [PATCH v6 5/7] hw/char/pl011: Consider TX FIFO overrun error
Posted by Peter Maydell 11 months, 3 weeks ago 
On Sat, 8 Feb 2025 at 16:39, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> When transmission is disabled, characters are still queued
> to the FIFO which eventually overruns. Report that error
> condition in the status register.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/char/pl011.c      | 20 ++++++++++++++++++++
>  hw/char/trace-events |  2 ++
>  2 files changed, 22 insertions(+)
>
> diff --git a/hw/char/pl011.c b/hw/char/pl011.c
> index 447f185e2d5..ef39ab666a2 100644
> --- a/hw/char/pl011.c
> +++ b/hw/char/pl011.c
> @@ -61,6 +61,9 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
>  /* Data Register, UARTDR */
>  #define DR_BE   (1 << 10)
>
> +/* Receive Status Register/Error Clear Register, UARTRSR/UARTECR */
> +#define RSR_OE  (1 << 3)
> +
>  /* Interrupt status bits in UARTRIS, UARTMIS, UARTIMSC */
>  #define INT_OE (1 << 10)
>  #define INT_BE (1 << 9)
> @@ -158,6 +161,16 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)
>      return pl011_is_fifo_enabled(s) ? PL011_FIFO_DEPTH : 1;
>  }
>
> +static bool pl011_is_tx_fifo_full(PL011State *s)
> +{
> +    if (pl011_is_fifo_enabled(s)) {
> +        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
> +        return fifo8_is_full(&s->xmit_fifo);
> +    }
> +    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
> +    return !fifo8_is_empty(&s->xmit_fifo);

More repetition of expressions, but anyway
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM
Re: [PATCH v6 5/7] hw/char/pl011: Consider TX FIFO overrun error
Posted by Peter Maydell 11 months, 3 weeks ago 
On Mon, 17 Feb 2025 at 14:29, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Sat, 8 Feb 2025 at 16:39, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> >
> > When transmission is disabled, characters are still queued
> > to the FIFO which eventually overruns. Report that error
> > condition in the status register.
> >
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > ---
> >  hw/char/pl011.c      | 20 ++++++++++++++++++++
> >  hw/char/trace-events |  2 ++
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/hw/char/pl011.c b/hw/char/pl011.c
> > index 447f185e2d5..ef39ab666a2 100644
> > --- a/hw/char/pl011.c
> > +++ b/hw/char/pl011.c
> > @@ -61,6 +61,9 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
> >  /* Data Register, UARTDR */
> >  #define DR_BE   (1 << 10)
> >
> > +/* Receive Status Register/Error Clear Register, UARTRSR/UARTECR */
> > +#define RSR_OE  (1 << 3)
> > +
> >  /* Interrupt status bits in UARTRIS, UARTMIS, UARTIMSC */
> >  #define INT_OE (1 << 10)
> >  #define INT_BE (1 << 9)
> > @@ -158,6 +161,16 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)
> >      return pl011_is_fifo_enabled(s) ? PL011_FIFO_DEPTH : 1;
> >  }
> >
> > +static bool pl011_is_tx_fifo_full(PL011State *s)
> > +{
> > +    if (pl011_is_fifo_enabled(s)) {
> > +        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
> > +        return fifo8_is_full(&s->xmit_fifo);
> > +    }
> > +    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
> > +    return !fifo8_is_empty(&s->xmit_fifo);
>
> More repetition of expressions, but anyway
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Here I propose to squash in this tweak:

--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -165,12 +165,13 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)

 static bool pl011_is_tx_fifo_full(PL011State *s)
 {
-    if (pl011_is_fifo_enabled(s)) {
-        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
-        return fifo8_is_full(&s->xmit_fifo);
-    }
-    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
-    return !fifo8_is_empty(&s->xmit_fifo);
+    bool fifo_enabled = pl011_is_fifo_enabled(s);
+    bool tx_fifo_full = fifo_enabled ?
+        fifo8_is_full(&s->xmit_fifo) : !fifo8_is_empty(&s->xmit_fifo);
+
+    trace_pl011_fifo_tx_is_full(fifo_enabled ? "FIFO" : "CHAR",
+                                tx_fifo_full);
+    return tx_fifo_full;
 }

thanks
-- PMM
Re: [PATCH v6 5/7] hw/char/pl011: Consider TX FIFO overrun error
Posted by Philippe Mathieu-Daudé 11 months, 3 weeks ago 
On 17/2/25 15:52, Peter Maydell wrote:
> On Mon, 17 Feb 2025 at 14:29, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Sat, 8 Feb 2025 at 16:39, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>>>
>>> When transmission is disabled, characters are still queued
>>> to the FIFO which eventually overruns. Report that error
>>> condition in the status register.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>>> ---
>>>   hw/char/pl011.c      | 20 ++++++++++++++++++++
>>>   hw/char/trace-events |  2 ++
>>>   2 files changed, 22 insertions(+)
>>>
>>> diff --git a/hw/char/pl011.c b/hw/char/pl011.c
>>> index 447f185e2d5..ef39ab666a2 100644
>>> --- a/hw/char/pl011.c
>>> +++ b/hw/char/pl011.c
>>> @@ -61,6 +61,9 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
>>>   /* Data Register, UARTDR */
>>>   #define DR_BE   (1 << 10)
>>>
>>> +/* Receive Status Register/Error Clear Register, UARTRSR/UARTECR */
>>> +#define RSR_OE  (1 << 3)
>>> +
>>>   /* Interrupt status bits in UARTRIS, UARTMIS, UARTIMSC */
>>>   #define INT_OE (1 << 10)
>>>   #define INT_BE (1 << 9)
>>> @@ -158,6 +161,16 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)
>>>       return pl011_is_fifo_enabled(s) ? PL011_FIFO_DEPTH : 1;
>>>   }
>>>
>>> +static bool pl011_is_tx_fifo_full(PL011State *s)
>>> +{
>>> +    if (pl011_is_fifo_enabled(s)) {
>>> +        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
>>> +        return fifo8_is_full(&s->xmit_fifo);
>>> +    }
>>> +    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
>>> +    return !fifo8_is_empty(&s->xmit_fifo);
>>
>> More repetition of expressions, but anyway
>> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> 
> Here I propose to squash in this tweak:
> 
> --- a/hw/char/pl011.c
> +++ b/hw/char/pl011.c
> @@ -165,12 +165,13 @@ static inline unsigned pl011_get_fifo_depth(PL011State *s)
> 
>   static bool pl011_is_tx_fifo_full(PL011State *s)
>   {
> -    if (pl011_is_fifo_enabled(s)) {
> -        trace_pl011_fifo_tx_is_full("FIFO", fifo8_is_full(&s->xmit_fifo));
> -        return fifo8_is_full(&s->xmit_fifo);
> -    }
> -    trace_pl011_fifo_tx_is_full("CHAR", !fifo8_is_empty(&s->xmit_fifo));
> -    return !fifo8_is_empty(&s->xmit_fifo);
> +    bool fifo_enabled = pl011_is_fifo_enabled(s);
> +    bool tx_fifo_full = fifo_enabled ?
> +        fifo8_is_full(&s->xmit_fifo) : !fifo8_is_empty(&s->xmit_fifo);
> +
> +    trace_pl011_fifo_tx_is_full(fifo_enabled ? "FIFO" : "CHAR",
> +                                tx_fifo_full);
> +    return tx_fifo_full;
>   }

Thank you, appreciated!

> 
> thanks
> -- PMM

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