linux-kernel - Re: [PATCH v3 3/4] mfd: tps65917: Add driver for the TPS65917 PMIC

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Date:	Fri, 23 May 2014 08:52:12 +0530
From:	Keerthy <a0393675@...com>
To:	Lee Jones <lee.jones@...aro.org>
CC:	Keerthy <j-keerthy@...com>, <devicetree@...r.kernel.org>,
	<robh+dt@...nel.org>, <mark.rutland@....com>,
	<sameo@...ux.intel.com>, <grant.likely@...aro.org>,
	<ian@...mlogic.co.uk>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <broonie@...aro.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] mfd: tps65917: Add driver for the TPS65917 PMIC

On Thursday 22 May 2014 05:18 PM, Lee Jones wrote:
>>>> The TPS65917 chip is a power management IC for Portable Navigation Systems
>>>> and Tablet Computing devices. It contains the following components:
>>>>
>>>>   - Regulators.
>>>>   - Over Temperature warning and Shut down.
>>>>
>>>> This patch adds support for tps65917 mfd device. At this time only
>>>> the regulator functionality is made available.
>>>>
>>>> Signed-off-by: Keerthy <j-keerthy@...com>
>>>> ---
>>>> v3 Changes:
>>>>
>>>>   * Header file formating
>>>>   * Changed the cache_type to REGCACHE_RBTREE
>>>>   * removed unnecessary code
>>>>   * Corrected documentation style
>>>>   * Added pm_power_off function
>>>>
>>>>   v2 Changes:
>>>>
>>>>   * Added volatile register check as some of the registers
>>>>     in the set are volatile.
>>>> drivers/mfd/Kconfig          |   12 +
>>>>   drivers/mfd/Makefile         |    1 +
>>>>   drivers/mfd/tps65917.c       |  594 +++++++++++++++++
>>>>   include/linux/mfd/tps65917.h | 1485 ++++++++++++++++++++++++++++++++++++++++++
>>>>   4 files changed, 2092 insertions(+)
>>>>   create mode 100644 drivers/mfd/tps65917.c
>>>>   create mode 100644 include/linux/mfd/tps65917.h
> [...]
>
>>>> +	for (i = 0; i < TPS65917_NUM_CLIENTS; i++) {
>>>> +		if (i == 0) {
>>>> +			tps65917->i2c_clients[i] = i2c;
>>> This is messy.  Move this line out of the loop and change the loop
>>> parameters to start from 1.  Then we can reduce all of this
>>> unnecessary indentation.
>> There is a common thing we do after if and else. Removing i == 0
>> part out of the
>> loop would mean repeating the common part. This way seems
>> better.
> Ah yes, good point.
>
>>>> +		} else {
>>>> +			tps65917->i2c_clients[i] =
>>>> +					i2c_new_dummy(i2c->adapter,
>>>> +						      i2c->addr + i);
>>>> +			if (!tps65917->i2c_clients[i]) {
>>>> +				dev_err(tps65917->dev,
>>>> +					"can't attach client %d\n", i);
>>>> +				ret = -ENOMEM;
>>>> +				goto err_i2c;
>>>> +			}
>>>> +
>>>> +			tps65917->i2c_clients[i]->dev.of_node = of_node_get(node);
>>> Don't forget to decrement the reference when you've finished with it.
>> I did not get this.
> Do you know what of_node_get() does?
>
> [...]
>
>>> What happens if !node?  Then no children get registered and this has
>>> all been a waste of time?
>> Only DT way is possible. This check is redundant. I will add a check
>> at the beginning for !node.
> If that's the case you should add 'depends on OF' in the Kconfig.
>
>>>> +struct tps65917_reg_init {
>>>> +	/*
>>>> +	 * 0: reload default values from OTP on warm reset
>>>> +	 * 1: maintain voltage from VSEL on warm reset
>>>> +	 */
>>>> +	bool warm_reset;
>>> Where is this used?
>>>
>>>> +	/*
>>>> +	 * 0: i2c selection of voltage
>>>> +	 * 1: pin selection of voltage.
>>>> +	 */
>>>> +	bool roof_floor;
>>> And this?
>>>
>>>> +	/*
>>>> +	 * For SMPS
>>>> +	 *
>>>> +	 * 0: Off
>>>> +	 * 1: AUTO
>>>> +	 * 2: ECO
>>>> +	 * 3: Forced PWM
>>>> +	 *
>>>> +	 * For LDO
>>>> +	 *
>>>> +	 * 0: Off
>>>> +	 * 1: On
>>>> +	 */
>>>> +	int mode_sleep;
>>> And this?
>>>
>>>> +	u8 vsel;
>>> And this?
>> All of the above can be used by regulator driver.
> Doesn't the regulator driver have its own header file?  Why are these
> in a shared file if they're not used anywhere else?
>
> [...]
>
>>>> +	if (pdata->mux_from_pdata) {
>>>> +		reg = pdata->pad1;
>>>> +		ret = regmap_write(tps65917->regmap[slave], addr, reg);
>>>> +		if (ret)
>>>> +			goto err_irq;
>>>> +	} else {
>>>> +		ret = regmap_read(tps65917->regmap[slave], addr, &reg);
>>>> +		if (ret)
>>>> +			goto err_irq;
>>>> +	}i
>>> What does the read do?  You're not doing anything with the value.
>> This pad1 and pad2 stuff is not needed. I will remove this.
> Then why is it in here?
>
> Did you copy this code from somewhere, if so, where?
>
> Okay, I just answered my own question.  There is so much common code
> in between this and palmas, there is no way I'm going to accept this
> driver.  Please merge it in with the palmas driver!
>
The chip is more like a subset of palmas with lot of register offset changes
and register bit field changes. Adding this would make it clumsy. There 
could
be lot of checks. That is why i chose to write a new driver.

Palmas driver already supports palmas variants and tps659038. Merging
this would mean more and more checks :-/.

Regards,
Keerthy
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