lkml.org 
[lkml]   [2016]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v7 10/14] usb: otg: add hcd companion support
From
Date


On 11/05/16 16:54, Rob Herring wrote:
> On Wed, May 04, 2016 at 04:47:18PM +0300, Roger Quadros wrote:
>> On 04/05/16 16:17, Rob Herring wrote:
>>> On Mon, May 02, 2016 at 03:18:53PM +0300, Roger Quadros wrote:
>>>> From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
>>>>
>>>> Since some host controller (e.g. EHCI) needs a companion host controller
>>>> (e.g. OHCI), this patch adds such a configuration to use it in the OTG
>>>> core.
>>>>
>>>> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
>>>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>>>> ---
>>>> Documentation/devicetree/bindings/usb/generic.txt | 3 +++
>>>> drivers/usb/common/usb-otg.c | 32 ++++++++++++++++-------
>>>> include/linux/usb/otg.h | 7 ++++-
>>>> 3 files changed, 32 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/usb/generic.txt b/Documentation/devicetree/bindings/usb/generic.txt
>>>> index f6866c1..1db1c33 100644
>>>> --- a/Documentation/devicetree/bindings/usb/generic.txt
>>>> +++ b/Documentation/devicetree/bindings/usb/generic.txt
>>>> @@ -27,6 +27,9 @@ Optional properties:
>>>> - otg-controller: phandle to otg controller. Host or gadget controllers can
>>>> contain this property to link it to a particular OTG
>>>> controller.
>>>> + - hcd-needs-companion: must be present if otg controller is dealing with
>>>> + EHCI host controller that needs a companion OHCI host
>>>> + controller.
>>>
>>> Don't you need to have a link to the companion controller node?
>>
>> primary and companion controllers are totally independent of each other
>> e.g. EHCI and OHCI. They are enabled by separate Kconfig options and
>> the system can operate with either or both of them enabled.
>>
>> At the OTG layer we don't have information as to whether we should be waiting
>> for both of them to register or not and hence need this "hcd-needs-companion" flag.
>
> What I mean is if you have 2 EHCI controllers with 2 companion
> controllers, don't you need to know which companion goes with which EHCI
> controller? Just like you do for the otg-controller property.
>

That is a very good point. I'm not very sure and it seems that current code won't work
with multiple EHCI + companion instances.

Alan, does USB core even know which EHCI and OHCI are linked to the same port
or the handoff is software transparent?

cheers,
-roger

\
 
 \ /
  Last update: 2016-05-11 16:41    [W:0.080 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site