linux-kernel - [PATCH V2 3/3] n_gsm: wake up ldisc tty before using it

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Date:	Wed, 27 May 2015 10:50:01 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	linux-kernel@...r.kernel.org, xinhuix.pan@...el.com,
	gregkh@...uxfoundation.org, alan@...ux.intel.com
Subject: [PATCH V2 3/3] n_gsm: wake up ldisc tty before using it

Wake up ldisc device before calling its driver to access the device.

Signed-off-by: Zhang Yanmin <yanmin.zhang@...el.com>

---

 drivers/tty/n_gsm.c | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 2c34c32..40671fa 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -62,6 +62,7 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/gsmmux.h>
+#include <linux/pm_runtime.h>
 
 static int debug;
 module_param(debug, int, 0600);
@@ -555,6 +556,27 @@ static int gsm_stuff_frame(const u8 *input, u8 *output, int len)
     return olen;
 }
 
+static int pm_runtime_get_sync_tty(struct tty_struct *tty)
+{
+    int ret = 0;
+
+    /*Wakeup parent as tty itself doesn't enable runtime*/
+    if (tty->dev->parent)
+        ret = pm_runtime_get_sync(tty->dev->parent);
+
+    return ret;
+}
+
+static int pm_runtime_put_tty(struct tty_struct *tty)
+{
+    int ret = 0;
+
+    if (tty->dev->parent)
+        ret = pm_runtime_put(tty->dev->parent);
+
+    return ret;
+}
+
 /**
  *    gsm_send    -    send a control frame
  *    @gsm: our GSM mux
@@ -1511,7 +1533,9 @@ static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
         return;
     dlci->retries = gsm->n2;
     dlci->state = DLCI_OPENING;
+    pm_runtime_get_sync_tty(gsm->tty);
     gsm_command(dlci->gsm, dlci->addr, SABM|PF);
+    pm_runtime_put_tty(gsm->tty);
     mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
 }
 
@@ -1533,7 +1557,9 @@ static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
         return;
     dlci->retries = gsm->n2;
     dlci->state = DLCI_CLOSING;
+    pm_runtime_get_sync_tty(gsm->tty);
     gsm_command(dlci->gsm, dlci->addr, DISC|PF);
+    pm_runtime_put_tty(gsm->tty);
     mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
 }
 
@@ -2286,7 +2312,9 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
             flags = *f++;
         switch (flags) {
         case TTY_NORMAL:
+            pm_runtime_get_sync_tty(gsm->tty);
             gsm->receive(gsm, *dp);
+            pm_runtime_put_tty(gsm->tty);
             break;
         case TTY_OVERRUN:
         case TTY_BREAK:
@@ -2957,6 +2985,7 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
 {
     struct gsm_dlci *dlci = tty->driver_data;
     struct tty_port *port = &dlci->port;
+    int ret;
 
     port->count++;
     tty_port_tty_set(port, tty);
@@ -2968,7 +2997,11 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
     /* Start sending off SABM messages */
     gsm_dlci_begin_open(dlci);
     /* And wait for virtual carrier */
-    return tty_port_block_til_ready(port, tty, filp);
+    pm_runtime_get_sync_tty(dlci->gsm->tty);
+    ret = tty_port_block_til_ready(port, tty, filp);
+    pm_runtime_put_tty(dlci->gsm->tty);
+
+    return ret;
 }
 
 static void gsmtty_close(struct tty_struct *tty, struct file *filp)
@@ -2986,11 +3019,14 @@ static void gsmtty_close(struct tty_struct *tty, struct file *filp)
     gsm = dlci->gsm;
     if (tty_port_close_start(&dlci->port, tty, filp) == 0)
         return;
+    pm_runtime_get_sync_tty(gsm->tty);
     gsm_dlci_begin_close(dlci);
     if (test_bit(ASYNCB_INITIALIZED, &dlci->port.flags)) {
         if (C_HUPCL(tty))
             tty_port_lower_dtr_rts(&dlci->port);
     }
+    pm_runtime_put_tty(gsm->tty);
+
     tty_port_close_end(&dlci->port, tty);
     tty_port_tty_set(&dlci->port, NULL);
     return;
@@ -3012,10 +3048,12 @@ static int gsmtty_write(struct tty_struct *tty, const unsigned char *buf,
     struct gsm_dlci *dlci = tty->driver_data;
     if (dlci->state == DLCI_CLOSED)
         return -EINVAL;
+    pm_runtime_get_sync_tty(dlci->gsm->tty);
     /* Stuff the bytes into the fifo queue */
     sent = kfifo_in_locked(dlci->fifo, buf, len, &dlci->lock);
     /* Need to kick the channel */
     gsm_dlci_data_kick(dlci);
+    pm_runtime_put_tty(dlci->gsm->tty);
     return sent;
 }
 
-- 
1.9.1

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