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gpu: nova-core: add helper function to wait on condition

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While programming the hardware, we frequently need to busy-wait until
a condition (like a given bit of a register to switch value) happens.

Add a basic `wait_on` helper function to wait on such conditions
expressed as a closure, with a timeout argument.

This is temporary as we will switch to `read_poll_timeout` [1] once it
is available.

Link: https://lore.kernel.org/lkml/20250220070611.214262-8-fujita.tomonori@gmail.com/ [1]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-11-ecf41ef99252@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Alexandre Courbot 2025-06-19 22:23:55 +09:00 committed by Danilo Krummrich
parent 94a0872143
commit a03c9bd953
1 changed files with 29 additions and 0 deletions
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29
drivers/gpu/nova-core/util.rs
View File

@ -1,5 +1,10 @@
// SPDX-License-Identifier: GPL-2.0
use core::time::Duration;
use kernel::prelude::*;
use kernel::time::Instant;
pub(crate) const fn to_lowercase_bytes<const N: usize>(s: &str) -> [u8; N] {
let src = s.as_bytes();
let mut dst = [0; N];
@ -19,3 +24,27 @@ pub(crate) const fn const_bytes_to_str(bytes: &[u8]) -> &str {
Err(_) => kernel::build_error!("Bytes are not valid UTF-8."),
}
}
/// Wait until `cond` is true or `timeout` elapsed.
///
/// When `cond` evaluates to `Some`, its return value is returned.
///
/// `Err(ETIMEDOUT)` is returned if `timeout` has been reached without `cond` evaluating to
/// `Some`.
///
/// TODO: replace with `read_poll_timeout` once it is available.
/// (https://lore.kernel.org/lkml/20250220070611.214262-8-fujita.tomonori@gmail.com/)
#[expect(dead_code)]
pub(crate) fn wait_on<R, F: Fn() -> Option<R>>(timeout: Duration, cond: F) -> Result<R> {
let start_time = Instant::now();
loop {
if let Some(ret) = cond() {
return Ok(ret);
}
if start_time.elapsed().as_nanos() > timeout.as_nanos() as i64 {
return Err(ETIMEDOUT);
}
}
}