linux-kernel - RE: [PATCH v2 1/1] mfd: intel_quark_i2c_gpio: Add Intel Quark X1000 I2C-GPIO MFD Driver

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Date:	Thu, 11 Dec 2014 09:50:43 +0000
From:	"Tan, Raymond" <raymond.tan@...el.com>
To:	Lee Jones <lee.jones@...aro.org>,
	"mturquette@...aro.org" <mturquette@...aro.org>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Chen, Alvin" <alvin.chen@...el.com>,
	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
	"Tan, Raymond" <raymond.tan@...el.com>
Subject: RE: [PATCH v2 1/1] mfd: intel_quark_i2c_gpio: Add Intel Quark X1000
 I2C-GPIO MFD Driver

Hi Mike and Lee Jones,

I've updated the patch (v3) with the input from previous reviews, hope this will help to facilitate a better review. I've kept the clk portion relatively unchanged except removing the usage of global variables, instead I've put them in a struct and set as drvdata for later use during the removal of the driver for unregistering the clk and clk_lookup.

Warm Regards, 

 Raymond Tan
Software Engineer
Malaysia IT Flex Services
INET: 8-253-0075
Flex Website: http://flexservices.intel.com 

> -----Original Message-----
> From: Lee Jones [mailto:lee.jones@...aro.org]
> Sent: Wednesday, November 26, 2014 12:53 AM
> To: Tan, Raymond; mturquette@...aro.org
> Cc: Samuel Ortiz; linux-kernel@...r.kernel.org; Chen, Alvin; Shevchenko,
> Andriy
> Subject: Re: [PATCH v2 1/1] mfd: intel_quark_i2c_gpio: Add Intel Quark
> X1000 I2C-GPIO MFD Driver
> 
> Crap!  Forgot to Cc Mike.
> 
> Fingers faster than brain.
> 
> > Mike,
> >
> > Something for you down below.
> >
> > > > > In Quark X1000, there's a single PCI device that provides both
> > > > > an I2C controller and a GPIO controller. This MFD driver will
> > > > > split the 2 devices for their respective drivers.
> > > > >
> > > > > This patch is based on Josef Ahmad's initial work for Quark enabling.
> > > > >
> > > > > Reviewed-by: Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com>
> > > > > Signed-off-by: Weike Chen <alvin.chen@...el.com>
> > > > > Signed-off-by: Raymond Tan <raymond.tan@...el.com>
> > > > > ---
> > > > >  drivers/mfd/Kconfig                |   11 ++
> > > > >  drivers/mfd/Makefile               |    1 +
> > > > >  drivers/mfd/intel_quark_i2c_gpio.c |  298
> > > > > ++++++++++++++++++++++++++++++++++++
> > > > >  3 files changed, 310 insertions(+)  create mode 100644
> > > > > drivers/mfd/intel_quark_i2c_gpio.c
> >
> > [...]
> >
> > > > > +	depends on COMMON_CLK
> > > >
> > > > I don't think you should depend on this.  Just use the API and
> > > > fail if it doesn't find the clock you're after.
> > >
> > > This was added to make sure the clk initialization and other clk related
> calls will work with the MFD.
> >
> > [...]
> >
> > > > > +struct clk *intel_quark_i2c_clk; struct clk_lookup
> > > > > +*intel_quark_i2c_clk_lookups;
> > > >
> > > > Why do these need to be global?
> > >
> > > I was trying to keep these as runtime allocated variables, and cleaned up
> with removal of the driver / upon error handling.
> >
> > They still can be.  But they need to be in a struct somewhere and not
> > global.
> >
> > [...]
> >
> > > > > +static int intel_quark_register_i2c_clk(struct pci_dev *pdev) {
> > > > > +	intel_quark_i2c_clk_lookups = devm_kcalloc(
> > > > > +
> > > > > +		&pdev->dev, INTEL_QUARK_I2C_NCLK,
> > > > > +		sizeof(*intel_quark_i2c_clk_lookups), GFP_KERNEL);
> > > > > +
> > > > > +	if (!intel_quark_i2c_clk_lookups)
> > > > > +		return -ENOMEM;
> > > > > +
> > > > > +	intel_quark_i2c_clk_lookups[0].dev_id =
> > > > > +INTEL_QUARK_I2C_CONTROLLER_CLK;
> > > > > +
> > > > > +	intel_quark_i2c_clk = clk_register_fixed_rate(
> > > > > +		&pdev->dev, INTEL_QUARK_I2C_CONTROLLER_CLK,
> NULL,
> > > > > +		CLK_IS_ROOT, INTEL_QUARK_I2C_CLK_HZ);
> > > > > +
> > > > > +	return clk_register_clkdevs(intel_quark_i2c_clk,
> > > > > +		intel_quark_i2c_clk_lookups,
> INTEL_QUARK_I2C_NCLK);
> > > >
> > > > We don't normally register clks from MFD.  Normally they are
> > > > registered in drivers/clk and fetched when a device requires them.
> > > > Why is this different?
> > >
> > > This is a static clk and on this platform, there's no clk hardware
> > > to have the clk driver to initialize this and add into the global
> > > struct for use later by i2c controller. The hardware on the platform
> > > itself is same, and the current driver (i2c_designware_platform)
> > > requires the clk for its operation. Due to this, I decided to have
> > > the clk initialize in the MFD before the device being added, which
> > > later will trigger the probe on the i2c controller driver.
> >
> > Mike,
> >
> > Can I get your input on this please?
> >
> > [...]
> >
> > > > > +	pdata = intel_quark_get_i2c_mode(pdev);
> > > > > +	if (IS_ERR(pdata))
> > > > > +		return PTR_ERR(pdata);
> > > >
> > > > Bring this functionality into here?
> > >
> > > Were you referring the contents of intel_quark_get_i2c_mode(), and
> avoid the additional function call instead?
> >
> > Right.  Please rid intel_quark_get_i2c_mode().
> >
> > [...]
> >
> 
> --
> Lee Jones
> Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source
> software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog