On Thu Jan 15, 2026 at 9:23 PM GMT, Deborah Brouwer wrote:
> The L2 power-on sequence and soft reset in Tyr previously relied on fixed
> sleeps followed by a single register check, since polling helpers were not
> available in Rust at the time.
>
> Now that read_poll_timeout() is available, poll the relevant registers
> until the hardware reports readiness or a timeout is reached.
>
> This avoids unnecessary delays on start-up.
>
> Signed-off-by: Deborah Brouwer <[email protected]>
> ---
> drivers/gpu/drm/tyr/driver.rs | 18 +++++++++---------
> drivers/gpu/drm/tyr/gpu.rs | 16 +++++++++-------
> 2 files changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
> index f0da58932702..60d01e3f101b 100644
> --- a/drivers/gpu/drm/tyr/driver.rs
> +++ b/drivers/gpu/drm/tyr/driver.rs
> @@ -8,6 +8,7 @@
> use kernel::devres::Devres;
> use kernel::drm;
> use kernel::drm::ioctl;
> +use kernel::io::poll;
> use kernel::new_mutex;
> use kernel::of;
> use kernel::platform;
> @@ -67,19 +68,18 @@ unsafe impl Sync for TyrData {}
> fn issue_soft_reset(dev: &Device<Bound>, iomem: &Devres<IoMem>) -> Result {
> regs::GPU_CMD.write(dev, iomem, regs::GPU_CMD_SOFT_RESET)?;
>
> - // TODO: We cannot poll, as there is no support in Rust currently, so we
> - // sleep. Change this when read_poll_timeout() is implemented in Rust.
> - kernel::time::delay::fsleep(time::Delta::from_millis(100));
> -
> - if regs::GPU_IRQ_RAWSTAT.read(dev, iomem)? &
> regs::GPU_IRQ_RAWSTAT_RESET_COMPLETED == 0 {
> - dev_err!(dev, "GPU reset failed with errno\n");
> + if let Err(e) = poll::read_poll_timeout(
> + || regs::GPU_IRQ_RAWSTAT.read(dev, iomem),
> + |status| *status & regs::GPU_IRQ_RAWSTAT_RESET_COMPLETED != 0,
> + time::Delta::from_millis(1),
> + time::Delta::from_millis(100),
> + ) {
> dev_err!(
> dev,
> - "GPU_INT_RAWSTAT is {}\n",
> + "GPU reset failed, GPU_IRQ_RAWSTAT is {}\n",
> regs::GPU_IRQ_RAWSTAT.read(dev, iomem)?
> );
> -
> - return Err(EIO);
> + return Err(e);
> }
>
> Ok(())
> diff --git a/drivers/gpu/drm/tyr/gpu.rs b/drivers/gpu/drm/tyr/gpu.rs
> index 6c582910dd5d..2ec56f763cc6 100644
> --- a/drivers/gpu/drm/tyr/gpu.rs
> +++ b/drivers/gpu/drm/tyr/gpu.rs
> @@ -4,9 +4,10 @@
> use kernel::device::Bound;
> use kernel::device::Device;
> use kernel::devres::Devres;
> +use kernel::io::poll;
> use kernel::platform;
> use kernel::prelude::*;
> -use kernel::time;
> +use kernel::time::Delta;
> use kernel::transmute::AsBytes;
>
> use crate::driver::IoMem;
> @@ -206,13 +207,14 @@ fn from(value: u32) -> Self {
> pub(crate) fn l2_power_on(dev: &Device<Bound>, iomem: &Devres<IoMem>) ->
> Result {
> regs::L2_PWRON_LO.write(dev, iomem, 1)?;
>
> - // TODO: We cannot poll, as there is no support in Rust currently, so we
> - // sleep. Change this when read_poll_timeout() is implemented in Rust.
> - kernel::time::delay::fsleep(time::Delta::from_millis(100));
> -
> - if regs::L2_READY_LO.read(dev, iomem)? != 1 {
> + if let Err(e) = poll::read_poll_timeout(
> + || regs::L2_READY_LO.read(dev, iomem),
> + |status| *status == 1,
> + Delta::from_millis(1),
> + Delta::from_millis(100),
> + ) {
This can be
poll::read_poll_timeout(...).inspect_err(|_| dev_err!(...))?;
Best,
Gary
> dev_err!(dev, "Failed to power on the GPU\n");
> - return Err(EIO);
> + return Err(e);
> }
>
> Ok(())
