Re: [PATCH-for-8.2 v4 04/10] hw/char/pl011: Extract pl011_write_txdata() from pl011_write()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 10/11/23 00:17, Richard Henderson wrote:
> On 11/9/23 11:28, Philippe Mathieu-Daudé wrote:
>> When implementing FIFO, this code will become more complex.
>> Start by factoring it out to a new pl011_write_txdata() function.
>> No functional change intended.
> 
> ...
>> @@ -262,19 +273,13 @@ static void pl011_write(void *opaque, hwaddr 
>> offset,
>>                           uint64_t value, unsigned size)
>>   {
>>       PL011State *s = (PL011State *)opaque;
>> -    unsigned char ch;
>>       trace_pl011_write(offset, value, pl011_regname(offset));
>>       switch (offset >> 2) {
>>       case 0: /* UARTDR */
>> -        /* ??? Check if transmitter is enabled.  */
>> -        ch = value;
>> -        /* XXX this blocks entire thread. Rewrite to use
>> -         * qemu_chr_fe_write and background I/O callbacks */
>> -        qemu_chr_fe_write_all(&s->chr, &ch, 1);
>> -        s->int_level |= INT_TX;
>> -        pl011_update(s);
>> +        s->readbuff = value;
> 
> Why the write to readbuff?

I think I wanted to use it when FIFO is disabled due to:

https://developer.arm.com/documentation/ddi0183/g/programmers-model/register-descriptions/line-control-register--uartlcr-h?lang=en

UARTLCR_H.FEN:

   Enable FIFOs:

   0 = FIFOs are disabled (character mode) that is, the FIFOs become
       1-byte-deep holding registers

   1 = transmit and receive FIFO buffers are enabled (FIFO mode).

and we don't have a fifo8_change_capacity() method.

Otherwise, not sure what for is this field... I'll see if we can
just remove it.