According to the dm_serial_ops documentation, pending() should:
> @return number of waiting characters, 0 for none, -ve on error
And:
> It is acceptable to return 1 if an indeterminant number
> of characters is waiting.
With the current implementation, we have:
* FIFO is full -> pending() returns 0
* FIFO is partially used -> pending() returns 1
* FIFO is empty -> pending() returns 1
This is not the same as what the documentation requires.
Moreover, since [1], arm reset now flushes all console devices
(including serial) before the cpu gets reset.
Because of the flawed logic:
=> reset # user calls reset
flush() is called
_serial_flush() is called
ops->pending(dev, false) # never returns false
# board hangs indefinitely without resetting.
Fix it by using AML_UART_TX_EMPTY instead of AML_UART_TX_FULL.
[1] commit c5f4cdb8eb60 ("console: Use flush() before panic and reset"),
Signed-off-by: Mattijs Korpershoek <mkorpersh...@baylibre.com>
---
Tested with:
=> reset # vim3 board no longer hangs
---
drivers/serial/serial_meson.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/serial/serial_meson.c b/drivers/serial/serial_meson.c
index d026f5a7a8e5..934de2ab2358 100644
--- a/drivers/serial/serial_meson.c
+++ b/drivers/serial/serial_meson.c
@@ -201,7 +201,10 @@ static int meson_serial_pending(struct udevice *dev, bool
input)
return true;
} else {
- return !(status & AML_UART_TX_FULL);
+ if (status & AML_UART_TX_EMPTY)
+ return false;
+
+ return true;
}
}
---
base-commit: a1fd9cb41fb1fda2283a089f9c97e5eed4d4940a
change-id: 20230606-fix-meson-serial-pending-890e11467215
Best regards,
--
Mattijs Korpershoek <mkorpersh...@baylibre.com>
