linux-kernel - Re: [PATCH 2/2] phy: driver for Conexant Digicolor internal USB PHY

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Date:	Tue, 31 Mar 2015 21:42:53 +0300
From:	Baruch Siach <baruch@...s.co.il>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Marek Vasut <marex@...x.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] phy: driver for Conexant Digicolor internal USB PHY

Hi Kishon,

On Tue, Mar 31, 2015 at 09:16:40PM +0530, Kishon Vijay Abraham I wrote:
> On Tuesday 31 March 2015 09:11 PM, Baruch Siach wrote:
> >On Tue, Mar 31, 2015 at 08:56:54PM +0530, Kishon Vijay Abraham I wrote:
> >>On Tuesday 31 March 2015 05:04 PM, Baruch Siach wrote:
> >>>On Sat, Mar 28, 2015 at 04:33:02PM +0100, Marek Vasut wrote:
> >>>>On Friday, March 27, 2015 at 05:36:29 AM, Baruch Siach wrote:
> >>>>>Add a driver for the USB PHY on the Conexant CX92755 SoC, from the
> >>>>>Digicolor series of SoCs. The PHY is connected to the on-chip chipidea
> >>>>>usb2 host.
> >>>>>
> >>>>>The hardware is somewhat similar to the phy-mxs-usb.c usb_phy, but it is
> >>>>>different enough to merit its own driver. Also, this driver uses the
> >>>>>generic phy infrastructure.
> >>>>
> >>>>the register set looks very similar to MXS one indeed. How is it different
> >>>>please ?
> >>>
> >>>Almost of the bits that are defined in the MXS USBPHY_CTRL register are not
> >>>defined in the Digicolor one. Some have different meaning, and some are
> >>>reserved. OTOH, the Digicolor USBPHY_CTRL register uses all bits in the 1-13
> >>>range. Also, the Digicolor phy does not have anatop registers.
> >>
> >>I think we should try adding support for this in the same driver.
> >
> >The only code that can actually be shared between the driver is the two lines
> >usb_phy .on_connect callback routine. The init sequence that takes most of the
> >digicolor driver is totally different. Using a single driver for both PHYs
> >does not make much sense, IMHO.
> >
> >Besides, phy-mxs-usb.c uses the deprecated usb_phy framework. So we first need
> >to port this driver to the generic phy framework.
> 
> Doesn't your driver also use the usb_phy framework?

My driver uses usb_phy only for the .notify_connect/.notify_disconnect 
callbacks, since there is no comparable functionality in the generic phy 
framework. But it doesn't make this driver any more similar to phy-mxs-usb.

My point is that merging the drives would require migrating phy-mxs-usb to 
generic phy. But this is just an added complication. The main reason I think 
the drivers should be separate is because they have very little in common, 
regardless of the framework they are using.

baruch

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