linux-kernel - Re: [PATCH 3/5] ARM: davinci: da8xx: add cfgchip2 to resources

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Date:	Wed, 16 Mar 2016 13:14:26 -0500
From:	David Lechner <david@...hnology.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Sekhar Nori <nsekhar@...com>,
	Kevin Hilman <khilman@...nel.org>,
	Alan Stern <stern@...land.harvard.edu>, Bin Liu <b-liu@...com>,
	Petr Kulhavy <petr@...ix.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH 3/5] ARM: davinci: da8xx: add cfgchip2 to resources

On 03/16/2016 12:38 PM, Sergei Shtylyov wrote:
> On 03/16/2016 07:57 AM, David Lechner wrote:
>
>> Also, I am not finding any existing data structure to pass the musb
>> set_mode
>> function to the phy in either usb_phy or usb_otg. Setting the mode
>> (host/peripheral/otg) is done in the same PHY register, so it seems
>> like it
>> should be implemented in the new phy driver as well.
>
>     Perhaps we'd have to sacrifice that functionality...

The device I am working on (LEGO MINDSTORMS EV3) has the port wired as 
peripheral only, so I don't think leaving this out is an option. Leaving 
it in OTG mode doesn't work because the required electrical connections 
are just not there.

>> I guess I could use a generic phy instead and use phy_set_drvdata() to
>> share
>> data between the phy driver and the musb driver. Does this sound like a
>> reasonable thing to do?
>
>     Not sure what you mean, could you elaborate?

I found another driver that essentially does what I was trying to 
explain here. See the sun4i_usb_phy_set_squelch_detect function in 
drivers/phy/phy-sun4i-usb.c:394[1] as an example. It is called at 
drivers/usb/musb/sunxi.c:160[2] and :167.

I would move the da8xx_musb_set_mode function from 
drivers/usb/musb/da8xx.c to the new drivers/phy/phy-da8xx-usb.c and call 
it in a similar manner to the sunix example I gave.


---

[1]: drivers/phy/phy-sun4i-usb.c

void sun4i_usb_phy_set_squelch_detect(struct phy *_phy, bool enabled)
{
struct sun4i_usb_phy *phy = phy_get_drvdata(_phy);

sun4i_usb_phy_write(phy, PHY_SQUELCH_DETECT, enabled ? 0 : 2, 2);
}
EXPORT_SYMBOL_GPL(sun4i_usb_phy_set_squelch_detect);



[2]: drivers/usb/musb/sunxi.c

static void sunxi_musb_pre_root_reset_end(struct musb *musb)
{
	struct sunxi_glue *glue = dev_get_drvdata(musb->controller->parent);

	sun4i_usb_phy_set_squelch_detect(glue->phy, false);
}