linux-kernel - Re: [PATCH v3] USB: PHY: Palmas USB Transceiver Driver

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Date:	Tue, 26 Mar 2013 12:21:00 +0200
From:	Felipe Balbi <balbi@...com>
To:	Graeme Gregory <gg@...mlogic.co.uk>
CC:	Kishon Vijay Abraham I <kishon@...com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"balbi@...com" <balbi@...com>, Rajendra Nayak <rnayak@...com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"rob@...dley.net" <rob@...dley.net>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"s-guiriec@...com" <s-guiriec@...com>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3] USB: PHY: Palmas USB Transceiver Driver

Hi,

On Tue, Mar 26, 2013 at 09:01:42AM +0000, Graeme Gregory wrote:
> >>> From: Graeme Gregory <gg@...mlogic.co.uk>
> >>>
> >>> This is the driver for the OTG transceiver built into the Palmas
> >>> chip. It
> >>> handles the various USB OTG events that can be generated by cable
> >>> insertion/removal.
> >>>
> >>> Signed-off-by: Graeme Gregory <gg@...mlogic.co.uk>
> >>> Signed-off-by: Moiz Sonasath <m-sonasath@...com>
> >>> Signed-off-by: Ruchika Kharwar <ruchika@...com>
> >>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> >>> Signed-off-by: Sebastien Guiriec <s-guiriec@...com>
> >>> ---
> >>
> >> I think this driver is more over the cable connection like vbus
> >> detetcion or ID pin detection.
> >> Then why not it is implemented based on extcon framework?
> >
> > extcon framework uses notification mechanism and Felipe dint like
> > using notification here. right Felipe?
> >>
> >> That way, generic usb driver (like tegra_usb driver) will get
> >> notification through extcon.
> >>
> >> We need this cable detection through extcon on our tegra solution
> >> through the Palmas.
> >>
> >>
> >> +#include <linux/of.h>
> >> +#include <linux/of_platform.h>
> >> +
> >> +static int palmas_usb_read(struct palmas *palmas, unsigned int reg,
> >> +               unsigned int *dest)
> >> +{
> >> +       unsigned int addr;
> >> +       int slave;
> >> +
> >> +       slave = PALMAS_BASE_TO_SLAVE(PALMAS_USB_OTG_BASE);
> >> +       addr = PALMAS_BASE_TO_REG(PALMAS_USB_OTG_BASE, reg);
> >> +
> >> +       return regmap_read(palmas->regmap[slave], addr, dest);
> >>
> >>
> >> Please use the generic api for palmas_read()/palmas_write(0 as it will
> >> be ease on debugging on register access.
> >> Direct regmap_read() does not help much on this.
> >
> > Graeme,
> > Any reason why you dint use palmas_read()/palmas_write here?
> > Btw palmas_read()/palmas_write() internally uses regmap APIs.
> Because I was not a fan of tightly coupling the child devices to the
> parent MFD. palmas_read/write were added by Laxman.

I guess regmap would also help abstracting SPI versus I2C connection.
IMHO, palmas_read/write should be removed.

Laxman's complaint that it doesn't help with debugging is utter
nonsense.

-- 
balbi

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