linux-kernel - Re: [PATCH v3 5/5] usb: musb: da8xx: Remove set

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Date:   Thu, 3 Nov 2016 18:42:18 +0100
From:   Alexandre Bailon <abailon@...libre.com>
To:     Bin Liu <b-liu@...com>, David Lechner <david@...hnology.com>,
        balbi@...nel.org, kishon@...com, khilman@...libre.com,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        nsekhar@...com
Subject: Re: [PATCH v3 5/5] usb: musb: da8xx: Remove set_mode callback

On 11/03/2016 06:27 PM, Bin Liu wrote:
> On Thu, Nov 03, 2016 at 12:18:53PM -0500, David Lechner wrote:
>> On 11/03/2016 10:26 AM, Alexandre Bailon wrote:
>>> The USB PHY is able to operate in OTG, host or peripheral.
>>> Some board may be wired to work act only as host or peripheral.
>>> In such case, the dr_mode property of controller must be set to
>>> host or peripheral. But doing that will also configure the PHY
>>> in host or peripheral mode whereas OTG is able to detect which
>>> role the USB controller should take.
>>> The PHY's host or peripheral mode are actually only useful when
>>> hardware doesn't allow OTG to detect it's role.
>>>
>>> The set_mode callback is used by the musb driver to set mode
>>> of the PHY. But in the case of DA8xx, the PHY have some issues.
>>> The OTG mode work correctly but the host and peripheral don't.
>>> In host mode, the PHY stops to work after the first disconnect.
>>> In device mode, the PHY doesn't detect any disconnect.
>>> As the OTG mode is working properly, let the PHY in OTG mode,
>>> whatever is the controller mode.
>>>
>>> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
>>> ---
>>> drivers/usb/musb/da8xx.c | 23 -----------------------
>>> 1 file changed, 23 deletions(-)
>>>
>>> diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
>>> index 6749aa1..581f830 100644
>>> --- a/drivers/usb/musb/da8xx.c
>>> +++ b/drivers/usb/musb/da8xx.c
>>> @@ -335,28 +335,6 @@ static irqreturn_t da8xx_musb_interrupt(int irq, void *hci)
>>> 	return ret;
>>> }
>>>
>>> -static int da8xx_musb_set_mode(struct musb *musb, u8 musb_mode)
>>
>> Bin suggested using some sort of quirks flag. So instead of removing
>> this callback, I think this is where to incorporate the quirks
>> flags.
>>
>> I suppose the quirks could be kernel config options. Perhaps someone
>> else has a better idea?
> 
> I didn't closely follow this thread, but I was thinking about to reuse
> musb->io.quirks, and define the quirks in device tree...
I have understood that.
It seems to be a better solution than what I did.
> 
> I am debugging an issue in dsps, and might need a quirk for the
> solution...
> 
> Regards,
> -Bin.
> 
Thanks,
Alexandre