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. [1] https://lore.kernel.org/lkml/20250220070611.214262-8-fujita.tomon...@gmail.com/ Signed-off-by: Alexandre Courbot <acour...@nvidia.com> --- drivers/gpu/nova-core/util.rs | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/gpu/nova-core/util.rs b/drivers/gpu/nova-core/util.rs index 332a64cfc6a9d7d787fbdc228887c0be53a97160..afb525228431a2645afe7bb34988e9537757b1d7 100644 --- a/drivers/gpu/nova-core/util.rs +++ b/drivers/gpu/nova-core/util.rs @@ -1,5 +1,10 @@ // SPDX-License-Identifier: GPL-2.0 +use core::time::Duration; + +use kernel::prelude::*; +use kernel::time::Ktime; + 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 +24,28 @@ 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.tomon...@gmail.com/) +#[expect(dead_code)] +pub(crate) fn wait_on<R, F: Fn() -> Option<R>>(timeout: Duration, cond: F) -> Result<R> { + let start_time = Ktime::ktime_get(); + + loop { + if let Some(ret) = cond() { + return Ok(ret); + } + + let cur_time = Ktime::ktime_get(); + if (cur_time - start_time).to_ns() > timeout.as_nanos() as i64 { + return Err(ETIMEDOUT); + } + } +} -- 2.49.0
