[PATCH] phy: mapphone-mdm6600: Fix write timeouts with shorter GPIO toggle interval

[Tony Lindgren <tony@atomide.com>]

I've noticed that when writing data to the modem the writes can time out
at some point eventually. Looks like kicking the modem idle GPIO every
600 ms instead of once a second fixes the issue. Note that this rate is
different from our runtime PM autosuspend rate MDM6600_MODEM_IDLE_DELAY_MS
that we still want to keep at 1 second, so let's add a separate define for
PHY_MDM6600_IDLE_KICK_MS.

Fixes: f7f50b2a7b05 ("phy: mapphone-mdm6600: Add runtime PM support for n_gsm on USB suspend")
Cc: Marcel Partap <mpartap@gmx.net>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Michael Scott <hashcode0f@gmail.com>
Cc: NeKit <nekit1000@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
---
 drivers/phy/motorola/phy-mapphone-mdm6600.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/phy/motorola/phy-mapphone-mdm6600.c b/drivers/phy/motorola/phy-mapphone-mdm6600.c
--- a/drivers/phy/motorola/phy-mapphone-mdm6600.c
+++ b/drivers/phy/motorola/phy-mapphone-mdm6600.c
@@ -20,6 +20,7 @@
 
 #define PHY_MDM6600_PHY_DELAY_MS	4000	/* PHY enable 2.2s to 3.5s */
 #define PHY_MDM6600_ENABLED_DELAY_MS	8000	/* 8s more total for MDM6600 */
+#define PHY_MDM6600_WAKE_KICK_MS	600	/* time on after GPIO toggle */
 #define MDM6600_MODEM_IDLE_DELAY_MS	1000	/* modem after USB suspend */
 #define MDM6600_MODEM_WAKE_DELAY_MS	200	/* modem response after idle */
 
@@ -525,8 +526,14 @@ static void phy_mdm6600_modem_wake(struct work_struct *work)
 
 	ddata = container_of(work, struct phy_mdm6600, modem_wake_work.work);
 	phy_mdm6600_wake_modem(ddata);
+
+	/*
+	 * The modem does not always stay awake 1.2 seconds after toggling
+	 * the wake GPIO, and sometimes it idles after about some 600 ms
+	 * making writes time out.
+	 */
 	schedule_delayed_work(&ddata->modem_wake_work,
-			      msecs_to_jiffies(MDM6600_MODEM_IDLE_DELAY_MS));
+			      msecs_to_jiffies(PHY_MDM6600_WAKE_KICK_MS));
 }
 
 static int __maybe_unused phy_mdm6600_runtime_suspend(struct device *dev)
-- 
2.25.0