Commits
Wang YanQing committed 8b5c913f7ee
serial: 8250_pci: Add WCH CH352 quirk to avoid Xscale detection
The code in 8250.c for detecting ARM/XScale UARTs says:
* Try writing and reading the UART_IER_UUE bit (b6).
* If it works, this is probably one of the Xscale platform's
* internal UARTs.
If the above passes, it then goes on to:
* It's an Xscale.
* We'll leave the UART_IER_UUE bit set to 1 (enabled).
However, the CH352 uses the UART_IER_UUE as the LOWPOWER function,
so it is readable and writable. According to the datasheet:
"LOWPOWER:When the bit is 1, close the internal benchmark
clock of serial port to set into low-power status.
So it essentially gets mis-detected as Xscale, and gets
powered down in the process. The device in question where
this was seen is listed by lspci as:
Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])
Re-using the 353 quirk which just sets flags to fixed and type
to 16550 is suitable for fixing the 352 as well.
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>