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

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Date:	Tue, 26 Mar 2013 14:07:08 +0200
From:	Felipe Balbi <balbi@...com>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	"balbi@...com" <balbi@...com>, Graeme Gregory <gg@...mlogic.co.uk>,
	Kishon Vijay Abraham I <kishon@...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 03:58:41PM +0530, Laxman Dewangan wrote:
> On Tuesday 26 March 2013 03:51 PM, Felipe Balbi wrote:
> >* PGP Signed by an unknown key
> >
> >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.
> palams read/write api uses the regmap only and hence not break
> anything on abstraction.
> in place of doing the following three statement in whole word, it
> provides wrapper of palmas_read()
> which actually does the same.
> 
> slave = PALMAS_BASE_TO_SLAVE(PALMAS_USB_OTG_BASE);
> addr = PALMAS_BASE_TO_REG(PALMAS_USB_OTG_BASE, reg);
> 
> regmap_read(palmas->regmap[slave], addr, dest);
> 
> Above 3 lines in all the places for resgister access or make single call:
> palmas_read(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_OTG_BASE, dest).
> 
> This function implement the above 3 lines.

now you have explained what the problem is. Makes much more sense to use
palmas_read() indeed. Duplicating the same thing all over the place
isn't very nice.

-- 
balbi

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