linux-kernel - RE: [PATCH v6 07/12] usb: otg: add OTG/dual-role core

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Date:	Thu, 7 Apr 2016 08:52:26 +0000
From:	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:	Roger Quadros <rogerq@...com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>
CC:	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"abrestic@...omium.org" <abrestic@...omium.org>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: RE: [PATCH v6 07/12] usb: otg: add OTG/dual-role core

Hi,

> From: Roger Quadros
> Sent: Tuesday, April 05, 2016 11:05 PM
> 
> It provides APIs for the following tasks
> 
> - Registering an OTG/dual-role capable controller
> - Registering Host and Gadget controllers to OTG core
> - Providing inputs to and kicking the OTG state machine
> 
> Provide a dual-role device (DRD) state machine.
> DRD mode is a reduced functionality OTG mode. In this mode
> we don't support SRP, HNP and dynamic role-swap.
> 
> In DRD operation, the controller mode (Host or Peripheral)
> is decided based on the ID pin status. Once a cable plug (Type-A
> or Type-B) is attached the controller selects the state
> and doesn't change till the cable in unplugged and a different
> cable type is inserted.
> 
> As we don't need most of the complex OTG states and OTG timers
> we implement a lean DRD state machine in usb-otg.c.
> The DRD state machine is only interested in 2 hardware inputs
> 'id' and 'b_sess_vld'.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---

I tried to implement this framework on my environment,
and it seemed work if I added a local hack to this patch :)

< snip >
> +	/* HCD will be started by OTG fsm when needed */
> +	mutex_lock(&otg->fsm.lock);
> +	if (otg->primary_hcd.hcd) {
> +		/* probably a shared HCD ? */
> +		if (usb_otg_hcd_is_primary_hcd(hcd)) {
> +			dev_err(otg_dev, "otg: primary host already registered\n");

My environment is arm64 / r8a7795, renesas_usbhs (as a gadget), EHCI and OHCI.
In this case, OHCI driver is also a primary_hcd. So, this error happened.
To avoid this, I assumes that the OHCI hcd is as shared_hcd like a patch below:

diff --git a/drivers/usb/common/usb-otg.c b/drivers/usb/common/usb-otg.c
index 41e762a..4d7f043 100644
--- a/drivers/usb/common/usb-otg.c
+++ b/drivers/usb/common/usb-otg.c
@@ -825,11 +825,16 @@ int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum,
 	if (otg->primary_hcd.hcd) {
 		/* probably a shared HCD ? */
 		if (usb_otg_hcd_is_primary_hcd(hcd)) {
+			if (hcd->driver->flags & HCD_USB11) {
+				dev_info(otg_dev, "this assumes usb 1.1 hc is as shared_hcd\n");
+				goto check_shared_hcd;
+			}
 			dev_err(otg_dev, "otg: primary host already registered\n");
 			goto err;
 		}
 
 		if (hcd->shared_hcd == otg->primary_hcd.hcd) {
+check_shared_hcd:
 			if (otg->shared_hcd.hcd) {
 				dev_err(otg_dev, "otg: shared host already registered\n");
 				goto err;

What do you think this local hack?
I also wonder if array of hcd may be good for both xHCI and EHCI/OHCI.
For example of xHCI:
 - otg->hcds[0] = primary_hcd
 - otg->hcds[1] = shared_hcd

For example of EHCI/OHCI:
 - otg->hcds[0] = primary_hcd of EHCI
 - otg->hcds[1] = primary_hcd of OHCI

Best regards,
Yoshihiro Shimoda