forked from Minki/linux
Revert "usb: pl2303: fix+improve the divsor based baud rate encoding method"
This reverts commit 57ce61aad7
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Revert all of the pl2303 changes that went into 3.12-rc1 and -rc2 as
they cause regressions on some versions of the chip. This will all be
revisited for later kernel versions when we can figure out how to handle
this in a way that does not break working devices.
Reported-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Frank Schäfer <fschaefer.oss@googlemail.com>
Acked-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -4,11 +4,6 @@
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* Copyright (C) 2001-2007 Greg Kroah-Hartman (greg@kroah.com)
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* Copyright (C) 2003 IBM Corp.
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*
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* Copyright (C) 2009, 2013 Frank Schäfer <fschaefer.oss@googlemail.com>
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* - fixes, improvements and documentation for the baud rate encoding methods
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* Copyright (C) 2013 Reinhard Max <max@suse.de>
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* - fixes and improvements for the divisor based baud rate encoding method
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*
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* Original driver for 2.2.x by anonymous
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*
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* This program is free software; you can redistribute it and/or
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@ -315,58 +310,21 @@ static void pl2303_encode_baudrate(struct tty_struct *tty,
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put_unaligned_le32(baud, buf);
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} else {
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/*
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* Divisor based baud rate encoding method
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*
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* NOTE: it's not clear if the type_0/1 chips
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* support this method
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*
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* divisor = 12MHz * 32 / baudrate = 2^A * B
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*
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* with
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*
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* A = buf[1] & 0x0e
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* B = buf[0] + (buf[1] & 0x01) << 8
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*
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* Special cases:
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* => 8 < B < 16: device seems to work not properly
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* => B <= 8: device uses the max. value B = 512 instead
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* Apparently the formula for higher speeds is:
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* baudrate = 12M * 32 / (2^buf[1]) / buf[0]
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*/
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/* Determine factors A and B */
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unsigned int A = 0;
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unsigned int B = 12000000 * 32 / baud; /* 12MHz */
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B <<= 1; /* Add one bit for rounding */
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while (B > (512 << 1) && A <= 14) {
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A += 2;
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B >>= 2;
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}
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if (A > 14) { /* max. divisor = min. baudrate reached */
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A = 14;
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B = 512;
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/* => ~45.78 baud */
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} else {
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B = (B + 1) >> 1; /* Round the last bit */
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}
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/* Handle special cases */
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if (B == 512)
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B = 0; /* also: 1 to 8 */
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else if (B < 16)
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/*
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* NOTE: With the current algorithm this happens
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* only for A=0 and means that the min. divisor
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* (respectively: the max. baudrate) is reached.
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*/
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B = 16; /* => 24 MBaud */
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/* Encode the baud rate */
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buf[3] = 0x80; /* Select divisor encoding method */
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unsigned tmp = 12000000 * 32 / baud;
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buf[3] = 0x80;
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buf[2] = 0;
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buf[1] = (A & 0x0e); /* A */
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buf[1] |= ((B & 0x100) >> 8); /* MSB of B */
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buf[0] = B & 0xff; /* 8 LSBs of B */
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/* Calculate the actual/resulting baud rate */
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if (B <= 8)
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B = 512;
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baud = 12000000 * 32 / ((1 << A) * B);
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buf[1] = (tmp >= 256);
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while (tmp >= 256) {
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tmp >>= 2;
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buf[1] <<= 1;
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}
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buf[0] = tmp;
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}
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/* Save resulting baud rate */
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