On Thu, 3 Oct 2024 at 08:10, Rasmus Villemoes <[email protected]> wrote: > > Before the previous patch, pasting a string of length x > > CONFIG_SERIAL_RX_BUFFER_SIZE results in getting the > last (x%CONFIG_SERIAL_RX_BUFFER_SIZE) characters from that string. > > With the previous patch, one instead gets the last > CONFIG_SERIAL_RX_BUFFER_SIZE characters repeatedly until the ->rd_ptr > catches up. > > Both behaviours are counter-intuitive, and happen because the code > that checks for a character available from the hardware does not > account for whether there is actually room in the software buffer to > receive it. Fix that by adding such accounting. This also brings the > software buffering more in line with how most hardware FIFOs > behave (first received characters are kept, overflowing characters are > dropped). > > Signed-off-by: Rasmus Villemoes <[email protected]> > --- > drivers/serial/serial-uclass.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-)
Reviewed-by: Simon Glass <[email protected]> > > diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c > index 05fe9645bee..28d7a202afc 100644 > --- a/drivers/serial/serial-uclass.c > +++ b/drivers/serial/serial-uclass.c > @@ -328,10 +328,11 @@ static int __serial_tstc(struct udevice *dev) > static int _serial_tstc(struct udevice *dev) > { > struct serial_dev_priv *upriv = dev_get_uclass_priv(dev); > - uint wr; > + uint wr, avail; > > - /* Read all available chars into the RX buffer */ > - while (__serial_tstc(dev)) { > + /* Read all available chars into the RX buffer while there's room */ > + avail = CONFIG_SERIAL_RX_BUFFER_SIZE - (upriv->wr_ptr - > upriv->rd_ptr); > + while (avail-- && __serial_tstc(dev)) { > wr = upriv->wr_ptr++ % CONFIG_SERIAL_RX_BUFFER_SIZE; > upriv->buf[wr] = __serial_getc(dev); > } > -- > 2.46.2 >
