linux-kernel - [PATCH] chipidea: Fix issue in reconnecing gadget without insmod/rmmod

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Date:   Tue, 11 Apr 2017 20:46:24 +0530
From:   Niranjan Dighe <niranjan.dighe@...il.com>
To:     Peter.Chen@...escale.com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] chipidea: Fix issue in reconnecing gadget without
 insmod/rmmod

Currently usb_gadget_connect() is called only through gadget
registration via composite_driver_probe(). As a result, after a
disconnection, if the role transitions to host and back to gadget,
the gadget is not recognized by the host anymore.
This is a typical scenario with an iAP device in the following
usecase -
conn iAP dev -> send roleswitch command -> roleswitch ourself
to gadget -> disconnect iAP device -> roleswitch back to host to
enumerate the device again -> reconnect device -> resend the
roleswitch command -> roleswitch ourself to gadget -> ISSUE.

To workaround this, do the following -

1. Restart OTG FSM on SLi interrupt and on switching role to gadget
so that device transitions to B_IDLE state from B_PERIPHERAL state.
A transition from B_IDLE to B_PERIPHERAL is needed to enable
interrups and restore the correct state of the chipidea controller
so that communication with host is possible

2. usb_gadget_connect() after roleswitch to gadget so that
gadget->ops->pullup() is called and D+ line is asserted. This
causes host to "see" the device and enumeration can happen.

Signed-off-by: Niranjan Dighe <niranjan.dighe@...il.com>
---
 drivers/usb/chipidea/debug.c | 10 +++++++++-
 drivers/usb/chipidea/udc.c   |  3 +++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
index a4f7db2..66c1485 100644
--- a/drivers/usb/chipidea/debug.c
+++ b/drivers/usb/chipidea/debug.c
@@ -16,7 +16,7 @@
 #include "udc.h"
 #include "bits.h"
 #include "otg.h"
-
+extern void ci_hdrc_otg_fsm_restart(struct ci_hdrc *);
 /**
  * ci_device_show: prints information about device capabilities and status
  */
@@ -325,6 +325,14 @@ static ssize_t ci_role_write(struct file *file, const char __user *ubuf,
 	ci_role_stop(ci);
 	ret = ci_role_start(ci, role);
 	enable_irq(ci->irq);
+
+	/* REVISIT - Avoid repeated FSM restart*/
+
+	if (role == CI_ROLE_GADGET) {
+		ci_hdrc_otg_fsm_restart(ci);
+		usb_gadget_connect(&ci->gadget);
+	}
+
 	pm_runtime_put_sync(ci->dev);

 	return ret ? ret : count;
diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index a0accd5..1e3b827 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -29,6 +29,8 @@
 #include "otg.h"
 #include "otg_fsm.h"

+extern void ci_hdrc_otg_fsm_restart(struct ci_hdrc *);
+
 /* control endpoint description */
 static const struct usb_endpoint_descriptor
 ctrl_endpt_out_desc = {
@@ -1881,6 +1883,7 @@ static irqreturn_t udc_irq(struct ci_hdrc *ci)
 				ci->driver->suspend(&ci->gadget);
 				usb_gadget_set_state(&ci->gadget,
 						USB_STATE_SUSPENDED);
+				ci_hdrc_otg_fsm_restart(ci);
 				spin_lock(&ci->lock);
 			}
 		}
-- 
2.1.4