[PATCH 0/2] TTY fix-ups for "TTY improve n_gsm support" series

[PATCH 0/2] TTY fix-ups for "TTY improve n_gsm support" series

[Gregory CLEMENT]

Hello,

Jiri found issues or things to improve in the v2 of the series "TTY
improve n_gsm support". However it was already applied. So this series
implements the needed changes.

For the second patch, as the commit "tty: n_gsm: Fix waking up upper
tty layer when room available" was not yet in mainline, it has no
SHA-1 ID yet. That's why I reference the same commit that the one
fixed by "TTY improve n_gsm support", as they should be applied in the
same order in stable branch than in mainline.

Gregory


Gregory CLEMENT (2):
  tty: n_gsm: Remove unnecessary test in gsm_print_packet()
  tty: n_gsm: Fix bogus i++ in gsm_data_kick

 drivers/tty/n_gsm.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

-- 
2.26.2

[PATCH 1/2] tty: n_gsm: Remove unnecessary test in gsm_print_packet()

[Gregory CLEMENT]

If the length is zero then the print_hex_dump_bytes won't output
anything, so testing the length before the call is unnecessary.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 drivers/tty/n_gsm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 69200bd411f7..4465dd04fead 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -504,8 +504,7 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
 	else
 		pr_cont("(F)");
 
-	if (dlen)
-		print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
+	print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
 }
 
 
-- 
2.26.2

[PATCH 2/2] tty: n_gsm: Fix bogus i++ in gsm_data_kick

[Gregory CLEMENT]

When submitting the previous fix "tty: n_gsm: Fix waking up upper tty
layer when room available". It was suggested to switch from a while to
a for loop, but when doing it, there was a remaining bogus i++.

This patch removes this i++ and also reorganizes the code making it more
compact.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 drivers/tty/n_gsm.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 4465dd04fead..0a29a94ec438 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -700,17 +700,9 @@ static void gsm_data_kick(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 		} else {
 			int i = 0;
 
-			for (i = 0; i < NUM_DLCI; i++) {
-				struct gsm_dlci *dlci;
-
-				dlci = gsm->dlci[i];
-				if (dlci == NULL) {
-					i++;
-					continue;
-				}
-
-				tty_port_tty_wakeup(&dlci->port);
-			}
+			for (i = 0; i < NUM_DLCI; i++)
+				if (gsm->dlci[i])
+					tty_port_tty_wakeup(&gsm->dlci[i]->port);
 		}
 	}
 }
-- 
2.26.2

[PATCH v2 0/3] TTY improve n_gsm support

[Gregory CLEMENT]

Hello,

This series is the second version of patch improving n_gms support
especially with TELIT LE910. However the fix should benefit to any
modem supporting cmux.

The first patch is just about improving debugging output.

The second one removes a tty optimization which make the LE910 hang.

The last one fixes an issue observed on the LE910 but should benefit
to all the modem. We observed that pretty quickly the transfer done
using the virtual tty were blocked. We found that it was due of a
wakeup to the real tty. Without this fix, the real tty wait for
indefinitely.

Thanks to Jiri Slaby for the review.

Changelog:
 v1 -> v2:
 - don't replace the pr_info by pr_debug
 - remove the superfluous printk("\n");
 - use --follow option with git log to find the original commit to fix
 - use tty_port_tty_wakeup
 - use 'for' loop instead of 'while'

Gregory

Gregory CLEMENT (3):
  tty: n_gsm: Improve debug output
  tty: n_gsm: Fix SOF skipping
  tty: n_gsm: Fix waking up upper tty layer when room available

 drivers/tty/n_gsm.c | 48 +++++++++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 23 deletions(-)

-- 
2.26.2

[PATCH v2 1/3] tty: n_gsm: Improve debug output

[Gregory CLEMENT]

Use appropriate print helpers for debug messages.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 drivers/tty/n_gsm.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index d77ed82a4840..67c8f8173023 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -504,18 +504,8 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
 	else
 		pr_cont("(F)");
 
-	if (dlen) {
-		int ct = 0;
-		while (dlen--) {
-			if (ct % 8 == 0) {
-				pr_cont("\n");
-				pr_debug("    ");
-			}
-			pr_cont("%02X ", *data++);
-			ct++;
-		}
-	}
-	pr_cont("\n");
+	if (dlen)
+		print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
 }
 
 
-- 
2.26.2

[PATCH v2 2/3] tty: n_gsm: Fix SOF skipping

[Gregory CLEMENT]

For at least some modems like the TELIT LE910, skipping SOF makes
transfers blocking indefinitely after a short amount of data
transferred.

Given the small improvement provided by skipping the SOF (just one
byte on about 100 bytes), it seems better to completely remove this
"feature" than make it optional.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 drivers/tty/n_gsm.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 67c8f8173023..d8d196645500 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -667,7 +667,6 @@ static void gsm_data_kick(struct gsm_mux *gsm)
 {
 	struct gsm_msg *msg, *nmsg;
 	int len;
-	int skip_sof = 0;
 
 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) {
 		if (gsm->constipated && msg->addr)
@@ -689,15 +688,10 @@ static void gsm_data_kick(struct gsm_mux *gsm)
 			print_hex_dump_bytes("gsm_data_kick: ",
 					     DUMP_PREFIX_OFFSET,
 					     gsm->txframe, len);
-
-		if (gsm->output(gsm, gsm->txframe + skip_sof,
-						len - skip_sof) < 0)
+		if (gsm->output(gsm, gsm->txframe, len) < 0)
 			break;
 		/* FIXME: Can eliminate one SOF in many more cases */
 		gsm->tx_bytes -= msg->len;
-		/* For a burst of frames skip the extra SOF within the
-		   burst */
-		skip_sof = 1;
 
 		list_del(&msg->list);
 		kfree(msg);
-- 
2.26.2

[PATCH v2 3/3] tty: n_gsm: Fix waking up upper tty layer when room available

[Gregory CLEMENT]

Warn the upper layer when n_gms is ready to receive data
again. Without this the associated virtual tty remains blocked
indefinitely.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 drivers/tty/n_gsm.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index d8d196645500..69200bd411f7 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -663,7 +663,7 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
  *	FIXME: lock against link layer control transmissions
  */
 
-static void gsm_data_kick(struct gsm_mux *gsm)
+static void gsm_data_kick(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 {
 	struct gsm_msg *msg, *nmsg;
 	int len;
@@ -695,6 +695,24 @@ static void gsm_data_kick(struct gsm_mux *gsm)
 
 		list_del(&msg->list);
 		kfree(msg);
+
+		if (dlci) {
+			tty_port_tty_wakeup(&dlci->port);
+		} else {
+			int i = 0;
+
+			for (i = 0; i < NUM_DLCI; i++) {
+				struct gsm_dlci *dlci;
+
+				dlci = gsm->dlci[i];
+				if (dlci == NULL) {
+					i++;
+					continue;
+				}
+
+				tty_port_tty_wakeup(&dlci->port);
+			}
+		}
 	}
 }
 
@@ -746,7 +764,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 	/* Add to the actual output queue */
 	list_add_tail(&msg->list, &gsm->tx_list);
 	gsm->tx_bytes += msg->len;
-	gsm_data_kick(gsm);
+	gsm_data_kick(gsm, dlci);
 }
 
 /**
@@ -1207,7 +1225,7 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
 		gsm_control_reply(gsm, CMD_FCON, NULL, 0);
 		/* Kick the link in case it is idling */
 		spin_lock_irqsave(&gsm->tx_lock, flags);
-		gsm_data_kick(gsm);
+		gsm_data_kick(gsm, NULL);
 		spin_unlock_irqrestore(&gsm->tx_lock, flags);
 		break;
 	case CMD_FCOFF:
@@ -2529,7 +2547,7 @@ static void gsmld_write_wakeup(struct tty_struct *tty)
 	/* Queue poll */
 	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 	spin_lock_irqsave(&gsm->tx_lock, flags);
-	gsm_data_kick(gsm);
+	gsm_data_kick(gsm, NULL);
 	if (gsm->tx_bytes < TX_THRESH_LO) {
 		gsm_dlci_data_sweep(gsm);
 	}
-- 
2.26.2

Re: [PATCH v2 0/3] TTY improve n_gsm support

[Gregory CLEMENT]

Hello,

> Hello,
>
> This series is the second version of patch improving n_gms support
> especially with TELIT LE910. However the fix should benefit to any
> modem supporting cmux.

You can just ignore the emails from this point, I forgot to remove the
remaining .patch!

Sorry for the noise

Gregory

>
> The first patch is just about improving debugging output.
>
> The second one removes a tty optimization which make the LE910 hang.
>
> The last one fixes an issue observed on the LE910 but should benefit
> to all the modem. We observed that pretty quickly the transfer done
> using the virtual tty were blocked. We found that it was due of a
> wakeup to the real tty. Without this fix, the real tty wait for
> indefinitely.
>
> Thanks to Jiri Slaby for the review.
>
> Changelog:
>  v1 -> v2:
>  - don't replace the pr_info by pr_debug
>  - remove the superfluous printk("\n");
>  - use --follow option with git log to find the original commit to fix
>  - use tty_port_tty_wakeup
>  - use 'for' loop instead of 'while'
>
> Gregory
>
> Gregory CLEMENT (3):
>   tty: n_gsm: Improve debug output
>   tty: n_gsm: Fix SOF skipping
>   tty: n_gsm: Fix waking up upper tty layer when room available
>
>  drivers/tty/n_gsm.c | 48 +++++++++++++++++++++++----------------------
>  1 file changed, 25 insertions(+), 23 deletions(-)
>
> -- 
> 2.26.2
>

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com