[PATCH v3 0/2] spi: axi-spi-engine: fix stale SYNC IRQ pending

[PATCH v3 0/2] spi: axi-spi-engine: fix stale SYNC IRQ pending

[Jonathan Santos]

Both spi_engine_setup() and spi_engine_trigger_enable() send a SYNC(1)
command and poll SYNC_ID, but never clear INT_PENDING[SYNC] afterward.
This leaves a stale pending bit that fires spuriously when INT_SYNC is
enabled later by some driver, causing premature transfer completion at
low SPI clock frequencies (more likely). Fix both functions by clearing
the pending bit after polling.

v3 summary:
* Added a dummy read after the clear command to flush the posted writes
  before dropping the lock.
* Link to v2: https://lore.kernel.org/linux-spi/cover.1790731588.git.Jonathan.Santos@analog.com/T/#t

v2 summary:
* Replaced "Link" tag for "Closes" tag.
* Included "Fixes" tag.
* Added new patch applying similar fix for the spi_engine_trigger_enable(),
  as pointed out by David.
* While at it, replaced plain "1000" by "1 * USEC_PER_MSEC" for better
  clarity.
* Link to v1: https://lore.kernel.org/linux-spi/04d51e99b8cddce51113db933d806e83848f04f5.1788313558.git.Jonathan.Santos@analog.com/T/#t
Jonathan Santos (2):
  spi: axi-spi-engine: fix stale SYNC IRQ pending
  spi: axi-spi-engine: fix stale SYNC IRQ pending in trigger_enable

 drivers/spi/spi-axi-spi-engine.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)


base-commit: 04434a1d0f311d76b1f15fa987918b471a0b8c6a
-- 
2.34.1

[PATCH v3 1/2] spi: axi-spi-engine: fix stale SYNC IRQ pending

[Jonathan Santos]

spi_engine_setup() sends a SYNC(1) command and polls SYNC_ID to confirm
it was parsed by the FPGA, but never clears the corresponding interrupt
pending bit (INT_PENDING[SYNC]). When the first real SPI transfer starts
and INT_SYNC is enabled, that stale pending bit fires immediately, causing
the IRQ handler to see the leftover SYNC_ID from setup, match it against
the current transfer's ID, and prematurely signal completion before the
hardware finishes.

This race manifests at low SPI clock frequencies (~2-3 MHz), where the
FPGA takes long enough to execute the transfer that handler is parsed
before it finishes. At higher SCLK rates the transfer completes fast
enough that the issue is masked.

Fix this by clearing INT_PENDING[SYNC] after the polled SYNC, ensuring no
stale interrupt is left pending.

Reported-by: Dennis Heinzel <dennis.heinzel@irs.systems>
Closes: https://ez.analog.com/linux-software-drivers/f/q-a/604145/axi-spi-engine-stale-sync-pending-can-complete-first-transfer-early-at-low-spi-clock-2-3-mhz
Fixes: 1d0ee0c9df31 ("spi: axi-spi-engine: wait for completion in setup")
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
 drivers/spi/spi-axi-spi-engine.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index 02bbc5d0cfc5..87c05cb064cc 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -887,6 +887,7 @@ static int spi_engine_setup(struct spi_device *device)
 	struct spi_controller *host = device->controller;
 	struct spi_engine *spi_engine = spi_controller_get_devdata(host);
 	unsigned int reg;
+	int ret;
 
 	if (device->mode & SPI_CS_HIGH)
 		spi_engine->cs_inv |= BIT(spi_get_chipselect(device, 0));
@@ -922,8 +923,15 @@ static int spi_engine_setup(struct spi_device *device)
 	writel_relaxed(SPI_ENGINE_CMD_SYNC(1),
 		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
 
-	return readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
-					  reg, reg == 1, 1, 1000);
+	ret = readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
+					 reg, reg == 1, 1, 1 * USEC_PER_MSEC);
+
+	/* Clear the stale SYNC pending bit so it doesn't fire when the IRQ is later enabled. */
+	writel_relaxed(SPI_ENGINE_INT_SYNC, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
+	/* Read back to flush posted write. */
+	readl_relaxed(spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
+
+	return ret;
 }
 
 static int spi_engine_transfer_one_message(struct spi_controller *host,
-- 
2.34.1

[PATCH v3 2/2] spi: axi-spi-engine: fix stale SYNC IRQ pending in trigger_enable

[Jonathan Santos]

spi_engine_trigger_enable() sends SYNC(1) and polls SYNC_ID, it never
clears the INT_PENDING[SYNC] bit afterward. This leaves a stale pending
interrupt that can fire spuriously when INT_SYNC is later enabled.

Simillarly to the fix on spi_engine_setup(), clear INT_PENDING[SYNC]
after polling the SYNC_ID.

Fixes: 8fc13b822c74 ("spi: axi-spi-engine: don't repeat mode config for offload")
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
 drivers/spi/spi-axi-spi-engine.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index 87c05cb064cc..ead5b295e680 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -1036,7 +1036,13 @@ static int spi_engine_trigger_enable(struct spi_offload *offload)
 		spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
 
 	ret = readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
-					 reg, reg == 1, 1, 1000);
+					 reg, reg == 1, 1, 1 * USEC_PER_MSEC);
+
+	/* Clear the stale SYNC pending bit so it doesn't fire when the IRQ is later enabled */
+	writel_relaxed(SPI_ENGINE_INT_SYNC, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
+	/* Read back to flush posted write. */
+	readl_relaxed(spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
+
 	if (ret)
 		return ret;
 
-- 
2.34.1

Re: [PATCH v3 0/2] spi: axi-spi-engine: fix stale SYNC IRQ pending

[Mark Brown]

On Wed, 07 Oct 2026 05:52:05 -0300, Jonathan Santos wrote:
> spi: axi-spi-engine: fix stale SYNC IRQ pending
> 
> Both spi_engine_setup() and spi_engine_trigger_enable() send a SYNC(1)
> command and poll SYNC_ID, but never clear INT_PENDING[SYNC] afterward.
> This leaves a stale pending bit that fires spuriously when INT_SYNC is
> enabled later by some driver, causing premature transfer completion at
> low SPI clock frequencies (more likely). Fix both functions by clearing
> the pending bit after polling.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-7.4

Thanks!

[1/2] spi: axi-spi-engine: fix stale SYNC IRQ pending
      https://git.kernel.org/broonie/misc/c/ea29c686f96a
[2/2] spi: axi-spi-engine: fix stale SYNC IRQ pending in trigger_enable
      https://git.kernel.org/broonie/misc/c/18febc10a353

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark