[PATCH] add synclink_gt custom hdlc idle

Add custom HDLC idle pattern feature.

It allows the user to specify an arbitrary 8 or 16 bit repeating pattern on
the transmit data pin between HDLC frames.

In most cases the idle pattern is continuous ones or flags as supported by off
the shelf synchronous controllers and defined in the ISO3309 standard.  Some
applications (radio/satellite modems, connections to legacy military hardware)
require non-standard patterns.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/synclink_gt.c

@@ -2515,7 +2515,8 @@ static int set_txidle(struct slgt_info *info, int idle_mode)
 	DBGINFO(("%s set_txidle(%d)\n", info->device_name, idle_mode));
 	spin_lock_irqsave(&info->lock,flags);
 	info->idle_mode = idle_mode;
-	tx_set_idle(info);
+	if (info->params.mode != MGSL_MODE_ASYNC)
+		tx_set_idle(info);
 	spin_unlock_irqrestore(&info->lock,flags);
 	return 0;
 }
@@ -3940,8 +3941,6 @@ static void async_mode(struct slgt_info *info)
 
 	msc_set_vcr(info);
 
-	tx_set_idle(info);
-
 	/* SCR (serial control)
 	 *
 	 * 15  1=tx req on FIFO half empty
@@ -4175,17 +4174,38 @@ static void hdlc_mode(struct slgt_info *info)
  */
 static void tx_set_idle(struct slgt_info *info)
 {
-	unsigned char val = 0xff;
+	unsigned char val;
+	unsigned short tcr;
 
-	switch(info->idle_mode)
-	{
-	case HDLC_TXIDLE_FLAGS:          val = 0x7e; break;
-	case HDLC_TXIDLE_ALT_ZEROS_ONES: val = 0xaa; break;
-	case HDLC_TXIDLE_ZEROS:          val = 0x00; break;
-	case HDLC_TXIDLE_ONES:           val = 0xff; break;
-	case HDLC_TXIDLE_ALT_MARK_SPACE: val = 0xaa; break;
-	case HDLC_TXIDLE_SPACE:          val = 0x00; break;
-	case HDLC_TXIDLE_MARK:           val = 0xff; break;
+	/* if preamble enabled (tcr[6] == 1) then tx idle size = 8 bits
+	 * else tcr[5:4] = tx idle size: 00 = 8 bits, 01 = 16 bits
+	 */
+	tcr = rd_reg16(info, TCR);
+	if (info->idle_mode & HDLC_TXIDLE_CUSTOM_16) {
+		/* disable preamble, set idle size to 16 bits */
+		tcr = (tcr & ~(BIT6 + BIT5)) | BIT4;
+		/* MSB of 16 bit idle specified in tx preamble register (TPR) */
+		wr_reg8(info, TPR, (unsigned char)((info->idle_mode >> 8) & 0xff));
+	} else if (!(tcr & BIT6)) {
+		/* preamble is disabled, set idle size to 8 bits */
+		tcr &= ~(BIT5 + BIT4);
+	}
+	wr_reg16(info, TCR, tcr);
+
+	if (info->idle_mode & (HDLC_TXIDLE_CUSTOM_8 | HDLC_TXIDLE_CUSTOM_16)) {
+		/* LSB of custom tx idle specified in tx idle register */
+		val = (unsigned char)(info->idle_mode & 0xff);
+	} else {
+		/* standard 8 bit idle patterns */
+		switch(info->idle_mode)
+		{
+		case HDLC_TXIDLE_FLAGS:          val = 0x7e; break;
+		case HDLC_TXIDLE_ALT_ZEROS_ONES:
+		case HDLC_TXIDLE_ALT_MARK_SPACE: val = 0xaa; break;
+		case HDLC_TXIDLE_ZEROS:
+		case HDLC_TXIDLE_SPACE:          val = 0x00; break;
+		default:                         val = 0xff;
+		}
 	}
 
 	wr_reg8(info, TIR, val);

include/linux/synclink.h

 /*
  * SyncLink Multiprotocol Serial Adapter Driver
  *
- * $Id: synclink.h,v 3.11 2006/02/06 21:20:29 paulkf Exp $
+ * $Id: synclink.h,v 3.13 2006/05/23 18:25:06 paulkf Exp $
  *
  * Copyright (C) 1998-2000 by Microgate Corporation
  *
@@ -97,6 +97,8 @@
 #define HDLC_TXIDLE_ALT_MARK_SPACE	4
 #define HDLC_TXIDLE_SPACE		5
 #define HDLC_TXIDLE_MARK		6
+#define HDLC_TXIDLE_CUSTOM_8            0x10000000
+#define HDLC_TXIDLE_CUSTOM_16           0x20000000
 
 #define HDLC_ENCODING_NRZ			0
 #define HDLC_ENCODING_NRZB			1