1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index 09fb55cf3be7..6638c5d9079d 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -281,6 +281,12 @@ static int pl2303_baudrate_encode_direct(int baud, enum pl2303_type type,
                                  4800, 7200, 9600, 14400, 19200, 28800, 38400,
                                  57600, 115200, 230400, 460800, 614400, 921600,
                                  1228800, 2457600, 3000000, 6000000 };
+        /*
+         * NOTE: The PL2303HX (tested with rev. 3A) also supports the following
+         * baud rates: 128000, 134400, 161280, 201600, 268800, 403200, 806400.
+         * As long as we are not using this encoding method for them, there is
+         * no point in complicating the code to support them.
+         */
         int i;
 
         /* Set baudrate to nearest supported value */
@@ -394,6 +400,12 @@ static void pl2303_encode_baudrate(struct tty_struct *tty,
          *    => supported by all chip types
          * 2) Divisor based method: encodes a divisor to a base value (12MHz*32)
          *    => supported by HX chips (and likely not by type_0/1 chips)
+         *
+         * NOTE: Although the divisor based baud rate encoding method is much
+         * more flexible, some of the standard baud rate values can not be
+         * realized exactly. But the difference is very small (max. 0.2%) and
+         * the device likely uses the same baud rate generator for both methods
+         * so that there is likley no difference.
          */
         if (type != HX)
                 baud = pl2303_baudrate_encode_direct(baud, type, buf);