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Commit c01af4fe authored by Frederic Berat's avatar Frederic Berat Committed by Greg Kroah-Hartman
Browse files

n_gsm : Flow control handling in Mux driver 



- Correcting handling of FCon/FCoff in order to respect 27.010 spec
- Consider FCon/off will overide all dlci flow control except for
  dlci0 as we must be able to send control frames.
- Dlci constipated handling according to FC, RTC and RTR values.
- Modifying gsm_dlci_data_kick and gsm_dlci_data_sweep according
  to dlci constipated value

Signed-off-by: default avatarFrederic Berat <fredericx.berat@intel.com>
Signed-off-by: default avatarRuss Gorby <russ.gorby@intel.com>
Signed-off-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 192b6041

drivers/tty/n_gsm.c

+57 −22
Original line number Diff line number Diff line
@@ -673,6 +673,8 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len, 
 *

 *	The tty device has called us to indicate that room has appeared in

 *	the transmit queue. Ram more data into the pipe if we have any

 *	If we have been flow-stopped by a CMD_FCOFF, then we can only

 *	send messages on DLCI0 until CMD_FCON

 *

 *	FIXME: lock against link layer control transmissions

 */
@@ -680,15 +682,19 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len, 
static void gsm_data_kick(struct gsm_mux *gsm)

{

	struct gsm_msg *msg = gsm->tx_head;

	struct gsm_msg *free_msg;

	int len;

	int skip_sof = 0;



	/* FIXME: We need to apply this solely to data messages */

	if (gsm->constipated)

		return;



	while (gsm->tx_head != NULL) {

		msg = gsm->tx_head;

	while (msg) {

		if (gsm->constipated && msg->addr) {

			msg = msg->next;

			continue;

		}

		if (gsm->dlci[msg->addr]->constipated) {

			msg = msg->next;

			continue;

		}

		if (gsm->encoding != 0) {

			gsm->txframe[0] = GSM1_SOF;

			len = gsm_stuff_frame(msg->data,
@@ -711,15 +717,19 @@ static void gsm_data_kick(struct gsm_mux *gsm) 
						len - skip_sof) < 0)

			break;

		/* FIXME: Can eliminate one SOF in many more cases */

		gsm->tx_head = msg->next;

		if (gsm->tx_head == NULL)

			gsm->tx_tail = NULL;

		gsm->tx_bytes -= msg->len;

		kfree(msg);

		/* For a burst of frames skip the extra SOF within the

		   burst */

		skip_sof = 1;



		if (gsm->tx_head == msg)

			gsm->tx_head = msg->next;

		free_msg = msg;

		msg = msg->next;

		kfree(free_msg);

	}

	if (!gsm->tx_head)

		gsm->tx_tail = NULL;

}



/**
@@ -738,6 +748,8 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) 
	u8 *dp = msg->data;

	u8 *fcs = dp + msg->len;



	WARN_ONCE(dlci->constipated, "%s: queueing from a constipated DLCI",

		__func__);

	/* Fill in the header */

	if (gsm->encoding == 0) {

		if (msg->len < 128)
@@ -944,6 +956,9 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm) 
			break;

		dlci = gsm->dlci[i];

		if (dlci == NULL || dlci->constipated) {

			if (dlci && (debug & 0x20))

				pr_info("%s: DLCI %d is constipated",

					__func__, i);

			i++;

			continue;

		}
@@ -973,6 +988,13 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci) 
	unsigned long flags;

	int sweep;



	if (dlci->constipated) {

		if (debug & 0x20)

			pr_info("%s: DLCI %d is constipated",

				__func__, dlci->addr);

		return;

	}



	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);

	/* If we have nothing running then we need to fire up */

	sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
@@ -1030,6 +1052,7 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci, 
{

	int  mlines = 0;

	u8 brk = 0;

	int fc;



	/* The modem status command can either contain one octet (v.24 signals)

	   or two octets (v.24 signals + break signals). The length field will
@@ -1041,19 +1064,27 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci, 
	else {

		brk = modem & 0x7f;

		modem = (modem >> 7) & 0x7f;

	};

	}



	/* Flow control/ready to communicate */

	if (modem & MDM_FC) {

	fc = (modem & MDM_FC) || !(modem & MDM_RTR);

	if (fc && !dlci->constipated) {

		if (debug & 0x20)

			pr_info("%s: DLCI %d START constipated (tx_bytes=%d)",

				__func__, dlci->addr, dlci->gsm->tx_bytes);

		/* Need to throttle our output on this device */

		dlci->constipated = 1;

	}

	if (modem & MDM_RTC) {

		mlines |= TIOCM_DSR | TIOCM_DTR;

	} else if (!fc && dlci->constipated) {

		if (debug & 0x20)

			pr_info("%s: DLCI %d END constipated (tx_bytes=%d)",

				__func__, dlci->addr, dlci->gsm->tx_bytes);

		dlci->constipated = 0;

		gsm_dlci_data_kick(dlci);

	}



	/* Map modem bits */

	if (modem & MDM_RTC)

		mlines |= TIOCM_DSR | TIOCM_DTR;

	if (modem & MDM_RTR)

		mlines |= TIOCM_RTS | TIOCM_CTS;

	if (modem & MDM_IC)
@@ -1209,17 +1240,21 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command, 
		gsm_control_reply(gsm, CMD_TEST, data, clen);

		break;

	case CMD_FCON:

		/* Modem wants us to STFU */

		gsm->constipated = 1;

		gsm_control_reply(gsm, CMD_FCON, NULL, 0);

		break;

	case CMD_FCOFF:

		/* Modem can accept data again */

		if (debug & 0x20)

			pr_info("%s: GSM END constipation", __func__);

		gsm->constipated = 0;

		gsm_control_reply(gsm, CMD_FCOFF, NULL, 0);

		gsm_control_reply(gsm, CMD_FCON, NULL, 0);

		/* Kick the link in case it is idling */

		gsm_data_kick(gsm);

		break;

	case CMD_FCOFF:

		/* Modem wants us to STFU */

		if (debug & 0x20)

			pr_info("%s: GSM START constipation", __func__);

		gsm->constipated = 1;

		gsm_control_reply(gsm, CMD_FCOFF, NULL, 0);

		break;

	case CMD_MSC:

		/* Out of band modem line change indicator for a DLCI */

		gsm_control_modem(gsm, data, clen);
@@ -2276,7 +2311,7 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp, 
			gsm->error(gsm, *dp, flags);

			break;

		default:

			WARN_ONCE("%s: unknown flag %d\n",

			WARN_ONCE(1, "%s: unknown flag %d\n",

			       tty_name(tty, buf), flags);

			break;

		}