lkml.org 
[lkml]   [2015]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.13.y-ckt 16/78] usb: dwc3: gadget: let us set lower max_speed
Date
3.13.11-ckt32 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben McCauley <ben.mccauley@garmin.com>

commit b9e51b2b1fda19143f48d182ed7a2943f21e1ae4 upstream.

In some SoCs, dwc3 is implemented as a USB2.0 only
core, meaning that it can't ever achieve SuperSpeed.

Currect driver always sets gadget.max_speed to
USB_SPEED_SUPER unconditionally. This can causes
issues to some Host stacks where the host will issue
a GetBOS() request and we will reply with a BOS
containing Superspeed Capability Descriptor.

At least Windows seems to be upset by this fact and
prints a warning that we should connect $this device
to another port.

[ balbi@ti.com : rewrote entire commit, including
source code comment to make a lot clearer what the
problem is ]

Signed-off-by: Ben McCauley <ben.mccauley@garmin.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
[ luis: backported to 3.16:
- used dev_vdbg() instead of dwc3_trace() ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/usb/dwc3/gadget.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 217cc175..a38ad1b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2604,12 +2604,33 @@ int dwc3_gadget_init(struct dwc3 *dwc)
}

dwc->gadget.ops = &dwc3_gadget_ops;
- dwc->gadget.max_speed = USB_SPEED_SUPER;
dwc->gadget.speed = USB_SPEED_UNKNOWN;
dwc->gadget.sg_supported = true;
dwc->gadget.name = "dwc3-gadget";

/*
+ * FIXME We might be setting max_speed to <SUPER, however versions
+ * <2.20a of dwc3 have an issue with metastability (documented
+ * elsewhere in this driver) which tells us we can't set max speed to
+ * anything lower than SUPER.
+ *
+ * Because gadget.max_speed is only used by composite.c and function
+ * drivers (i.e. it won't go into dwc3's registers) we are allowing this
+ * to happen so we avoid sending SuperSpeed Capability descriptor
+ * together with our BOS descriptor as that could confuse host into
+ * thinking we can handle super speed.
+ *
+ * Note that, in fact, we won't even support GetBOS requests when speed
+ * is less than super speed because we don't have means, yet, to tell
+ * composite.c that we are USB 2.0 + LPM ECN.
+ */
+ if (dwc->revision < DWC3_REVISION_220A)
+ dev_vdbg(dwc->dev, "Changing max_speed on rev %08x\n",
+ dwc->revision);
+
+ dwc->gadget.max_speed = dwc->maximum_speed;
+
+ /*
* REVISIT: Here we should clear all pending IRQs to be
* sure we're starting from a well known location.
*/
--
1.9.1


\
 
 \ /
  Last update: 2015-12-17 02:21    [W:0.264 / U:1.312 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site