On 02/03/17 14:17, Johan Hovold wrote:
On Tue, Feb 28, 2017 at 12:51:24PM +0000, Ian Abbott wrote:
If a BM type chip has iSerialNumber set to 0 in its EEPROM, an incorrect
value is read from the bcdDevice field of the USB descriptor, making it
look like an AM type chip. Attempt to correct this in
ftdi_determine_type() by attempting to read the latency timer for an AM
type chip. If that succeeds, assume it is a BM type chip.
Currently, read_latency_timer() bails out without reading the latency
timer for an AM type chip, so factor out the guts of
read_latency_timer() into a new function _read_latency_timer() that
attempts to read the latency timer regardless of chip type, and returns
either the latency timer value or a negative error number.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/usb/serial/ftdi_sio.c | 38 ++++++++++++++++++++++++++++++--------
1 file changed, 30 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 72314734dfd0..a1b90f4184a7 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1609,9 +1623,17 @@ static void ftdi_determine_type(struct usb_serial_port *port)
priv->baud_base = 12000000 / 16;
} else if (version < 0x400) {
/* Assume it's an FT8U232AM (or FT8U245AM) */
- /* (It might be a BM because of the iSerialNumber bug,
- * but it will still work as an AM device.) */
priv->chip_type = FT8U232AM;
+ /*
+ * It might be a BM type because of the iSerialNumber bug.
+ * If the latency timer is readable, assume it is BM type.
+ */
+ if (_read_latency_timer(port) >= 0) {
Would it be possible to only try to read the latency timer when
iSerialNumber is 0?
Okay, I'll change that in v2 patch series.
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Web: http://www.mev.co.uk/ )=-
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