On Thu, Mar 21, 2013 at 11:06 AM, Peter Chen <peter.chen@xxxxxxxxxxxxx> wrote:
> On Wed, Mar 20, 2013 at 01:04:33PM +0200, Alexander Shishkin wrote:
>> Peter Chen <peter.chen@xxxxxxxxxxxxx> writes:
>>
>> > On Fri, Mar 15, 2013 at 05:17:08PM +0200, Alexander Shishkin wrote:
>> >>
>> >> > Eg, for tablet or phone, the dr_mode may be "gadget", but the
>> >> > otg_capable = 1.
>> >>
>> >> No, because dr_mode indicates controller's capability, and not the
>> >> "current" mode of operation. Why would anyone want to put *that* in a
>> >> DT?
>> >>
>> >
>> > OK, now I totally understand your mind of this problem. In fact, dr_mode
>> > is NOT controller's capability, even at its original place:
>> > (Documentation/devicetree/bindings/usb/fsl-usb.txt or nvidia, tegra20-ehci.txt)
>> > dr_mode is the usb working mode.
>> >
>> > When we design USB system, the requirements are differ from products
>> > to products.
>> > The phone/tablet device may only wants itself as gadget
>> > device, it needs to be no-response when there is a usb device plug in
>> > (eg usb keyboard with Micro B-to-A cable).
>> >
>> > The car entertainment system or other Standard-A port system do not want
>> > to be enumerated when it plugs to notebook using Standard A-to-A cable.
>>
>> Bah. Of course, you're right. We're stuck with dr_mode till people learn
>> to design middleware stacks that can handle being both host and
>> peripheral.
>>
>> > So, currently, even most of controllers are otg-capable, still most
>> > of designs are one working mode designed. The reason why we design
>> > the dr_mode is that we want controller working mode to be decided
>> > by DT without re-compile the kernel by build out the host/gadget driver.
>>
>> Ok, so then how about introducing *one* more parameter, something like
>> "dr_cap", which
>> 1) when specified, supersedes DCCPARAMS, so no need to read that
>> register any more;
>> 2) when unspecified, use DCCPARAMS;
>> 3) can be one of "host", "peripheral", "otg", "dual_role":
>> - host, peripheral: initialize one role only, stick to that, no otg;
>> - dual_role: initialize both roles, no otg;
>> - otg: both roles, ci->is_otg == true.
>
>>
>> Another question now is, do we need "dual_role" variant for the dr_mode
>> parameter?
>>
>
> "dr_cap" is a good idea to indicate controller's capability, but when
> it combines with "dr_mode", things will be more complicated.
> Eg, how we initialize roles, depends on dr_cap or dr_mode? Besides, we
> need to some judgements if dr_mode and dr_cap are conflict or not.
> Since we already have DCCPARAMS check at each role's init, I suggest
> we only need "otg_cap", it only indicates if otg is capable or not.
> We can do things like below:
>
> dr_mode: "host", "peripheral", "otg"
> otg_cap; false, true
>
> 1) For dr_mode usage, it is used like sascha's patch.
> 2) Then we decide ci->is_otg:
> if (otg_cap is existed)
> ci->is_otg = otg_cap;
> else
> read DDCPARMAS;
> if (both DC and HC are 1)
> ci->is_otg = 1;
> else
> ci->is_otg = 0;
>
> 3) if (ci->roles[CI_ROLE_HOST] && ci->roles[CI_ROLE_GADGET] && ci->is_otg)
> do_otg_init; /* Eg, enable ID interrupt at otgsc */
> 4) At ci_irq:
> if (ci->is_otg)
> otgsc = hw_read(ci, OP_OTGSC, ~0);
>
> /* Since id is only enabled at both roles are enabled,
> * if dr_mode = peripheral and ci_is_otg = true, code will
> * not handle id change.
> */
> if (ci->is_otg && (otgsc & OTGSC_IDIE) && (otgsc & OTGSC_IDIS)) {
> handle id interrupt;
> }
>
> /*
> * Handle vbus change interrupt, it indicates device connection
> * and disconnection events.
> */
> if (ci->is_otg && (otgsc & OTGSC_BSVIE)
> && (otgsc & OTGSC_BSVIS)) {
> handle vbus interrupt;
> }
>
> Besides, at my patch, I always build otg.c, I don't think
> we need to give otg.c a config, this just like we don't
> need to have a config for otg capable. I will
> move all otgsc access to under the condition of ci->is_otg.
>
Alex, I would like to post dual-role/vbus patch recently. Do you have
further suggestion for how to access otgsc? If not, I will
use the way I showed above.
--
BR,
Peter Chen
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