On Wed, Sep 11, 2024 at 6:35 AM Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> wrote: > > On 10/09/2024 05:54, Alistair Francis wrote: > > > The current approach of using qemu_chr_fe_write() and ignoring the > > return values results in dropped characters [1]. > > > > Let's update the SiFive UART to use a async sifive_uart_xmit() function > > to transmit the characters and apply back pressure to the guest with > > the SIFIVE_UART_TXFIFO_FULL status. > > > > This should avoid dropped characters and more realisticly model the > > hardware. > > Does the UART work reliably using the fifo8_*_bufptr() functions? One of the
I haven't noticed any issues. > motivations for my recent Fifo8 series is that these functions don't handle > the > wraparound correctly, unlike the fifo8_*_buf() functions in my recent Fifo8 > series > which do. This was the cause of Phil's async issue in > https://mail.gnu.org/archive/html/qemu-devel/2024-07/msg05028.html. I'm not sure if it matters here characters = fifo8_peek_bufptr(&s->tx_fifo, fifo8_num_used(&s->tx_fifo), &numptr); ret = qemu_chr_fe_write(&s->chr, characters, numptr); if (ret >= 0) { /* We wrote the data, actually pop the fifo */ fifo8_pop_bufptr(&s->tx_fifo, ret, NULL); } I don't care how many characters are returned from fifo8_peek_bufptr(), I'll just write them and then pop that number with fifo8_pop_bufptr() If fifo8_is_empty() isn't empty I re-add the watcher for qemu_chr_fe_add_watch() Alistair
