[PATCH v2] drm/tyr: use read_poll_timeout

[PATCH v2] drm/tyr: use read_poll_timeout

[Deborah Brouwer]

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 <deborah.brouwer@collabora.com>
---
Changes in v2:
- Changed the commit message prefix to drm/tyr
- Replace if-let-Err blocks with inspect_err()
- Remove redundant register read from issue_soft_reset() error path,
  to avoid nested error handling
- Link to v1: https://lore.kernel.org/rust-for-linux/20260115212355.201628-1-deborah.brouwer@collabora.com/

 drivers/gpu/drm/tyr/driver.rs | 22 ++++++++--------------
 drivers/gpu/drm/tyr/gpu.rs    | 18 +++++++++---------
 2 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index f0da58932702..2a45d0288825 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;
@@ -67,20 +68,13 @@ 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");
-        dev_err!(
-            dev,
-            "GPU_INT_RAWSTAT is {}\n",
-            regs::GPU_IRQ_RAWSTAT.read(dev, iomem)?
-        );
-
-        return Err(EIO);
-    }
+    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),
+    )
+    .inspect_err(|_| dev_err!(dev, "GPU reset failed."))?;
 
     Ok(())
 }
diff --git a/drivers/gpu/drm/tyr/gpu.rs b/drivers/gpu/drm/tyr/gpu.rs
index 3072562e36e5..bfbf2a1d80e6 100644
--- a/drivers/gpu/drm/tyr/gpu.rs
+++ b/drivers/gpu/drm/tyr/gpu.rs
@@ -6,9 +6,10 @@
 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 kernel::uapi;
 
@@ -204,14 +205,13 @@ 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 {
-        dev_err!(dev, "Failed to power on the GPU\n");
-        return Err(EIO);
-    }
+    poll::read_poll_timeout(
+        || regs::L2_READY_LO.read(dev, iomem),
+        |status| *status == 1,
+        Delta::from_millis(1),
+        Delta::from_millis(100),
+    )
+    .inspect_err(|_| dev_err!(dev, "Failed to power on the GPU."))?;
 
     Ok(())
 }
-- 
2.52.0

Re: [PATCH v2] drm/tyr: use read_poll_timeout

[Alice Ryhl]

On Mon, Jan 19, 2026 at 12:26:45PM -0800, 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 <deborah.brouwer@collabora.com>

Overall looks good to me.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v2] drm/tyr: use read_poll_timeout

[Alice Ryhl]

On Mon, Jan 19, 2026 at 12:26:45PM -0800, 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 <deborah.brouwer@collabora.com>

Merged into drm-rust-next, thanks!