On Thu, Dec 12, 2024 at 06:21:59PM +0100, Paolo Bonzini wrote:
> Date: Thu, 12 Dec 2024 18:21:59 +0100
> From: Paolo Bonzini <pbonz...@redhat.com>
> Subject: [PATCH 2/7] rust: pl011: match break logic of C version
> X-Mailer: git-send-email 2.47.1
>
> Check loopback_enabled(), not fifo_enabled(), like the C code.
>
> Also, set_break_error() must not happen until the break is read from
> the FIFO.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> rust/hw/char/pl011/src/device.rs | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
Now the logic here matches C version, so
Reviewed-by: Zhao Liu <zhao1....@intel.com>
But...
> diff --git a/rust/hw/char/pl011/src/device.rs
> b/rust/hw/char/pl011/src/device.rs
> index 41220c99a83..c6a8dbe1af4 100644
> --- a/rust/hw/char/pl011/src/device.rs
> +++ b/rust/hw/char/pl011/src/device.rs
> @@ -465,9 +465,8 @@ pub fn can_receive(&self) -> bool {
> }
>
> pub fn event(&mut self, event: QEMUChrEvent) {
> - if event == bindings::QEMUChrEvent::CHR_EVENT_BREAK &&
> !self.fifo_enabled() {
> + if event == bindings::QEMUChrEvent::CHR_EVENT_BREAK &&
> !self.loopback_enabled() {
> self.put_fifo(DATA_BREAK);
> - self.receive_status_error_clear.set_break_error(true);
> }
> }
>
...but when I double-check where to set up the rsr, I realized that the
rust version and the C version seem to be inconsistent?
C:
static uint32_t pl011_read_rxdata(PL011State *s)
{
...
c = s->read_fifo[s->read_pos];
...
s->rsr = c >> 8;
...
}
Rust:
pub fn read(&mut self, offset: hwaddr, _size: c_uint) ->
std::ops::ControlFlow<u64, u64> {
...
std::ops::ControlFlow::Break(match RegisterOffset::try_from(offset) {
...
Ok(DR) => {
...
let c = self.read_fifo[self.read_pos];
...
// Update error bits.
self.receive_status_error_clear = c.to_be_bytes()[3].into();
...
}
...
}
`to_be_bytes()` retures a byte array in big-endian byte order [*], so rust
accesses the first 8 bits and C accesses the last 24 bits, am I understanding
this correctly and which one is correct?
IIUC, I guess Rust should uses to_be_bytes()[2].
[*]: https://doc.rust-lang.org/std/primitive.u32.html#method.to_be_bytes
Regards,
Zhao
