linux-kernel - Re: [PATCH v6 3/6] mfd: ti_am335x_tscadc: Remove unwanted reg_se

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Message-ID: <54BF7C14.1080907@ti.com>
Date:	Wed, 21 Jan 2015 15:44:44 +0530
From:	Vignesh R <vigneshr@...com>
To:	Lee Jones <lee.jones@...aro.org>
CC:	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Brad Griffis <bgriffis@...com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Sanjeev Sharma <sanjeev_sharma@...tor.com>,
	Jan Kardell <jan.kardell@...liq.com>,
	Felipe Balbi <balbi@...com>, Wolfram Sang <wsa@...-dreams.de>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-iio@...r.kernel.org>, <linux-input@...r.kernel.org>
Subject: Re: [PATCH v6 3/6] mfd: ti_am335x_tscadc: Remove unwanted reg_se_cache
 save



On Tuesday 20 January 2015 09:34 PM, Lee Jones wrote:
> On Tue, 20 Jan 2015, R, Vignesh wrote:
>> On 1/20/2015 5:23 PM, Lee Jones wrote:
>>> On Wed, 07 Jan 2015, Vignesh R wrote:
>>>
>>>> In one shot mode, sequencer automatically disables all enabled steps at
>>>> the end of each cycle. (both ADC steps and TSC steps) Hence these steps
>>>> need not be saved in reg_se_cache for clearing these steps at a later
>>>> stage.
>>>> Also, when ADC wakes up Sequencer should not be busy executing any of the
>>>> config steps except for the charge step. Previously charge step was 1 ADC
>>>> clock cycle and hence it was ignored.
>>>> TSC steps are always disabled at the end of each conversion cycle, hence
>>>> there is no need to explicitly disable TSC steps by writing 0 to REG_SE.
>>>>
>>>> Signed-off-by: Vignesh R <vigneshr@...com>
>>>> ---
>>>>
>>>> v5:
>>>>  - Remove unnecessary clearing of REG_SE
>>>>
>>>>  drivers/mfd/ti_am335x_tscadc.c       | 13 +++++--------
>>>>  include/linux/mfd/ti_am335x_tscadc.h |  1 +
>>>>  2 files changed, 6 insertions(+), 8 deletions(-)
>>>
>>> Looks fine.
>>>
>>> For my own reference:
>>>   Acked-by: Lee Jones <lee.jones@...aro.org>
>>>
>>> Can this patch be applied on its own?
>>>
>>
>> I prefer to wait until input patches are picked up.
> 
> I have no problem with that, but is there a technical reason why?
> 

Nothing, in particular. This patch alone has no impact on the
performance of TSC/ADC unit. Patch 2/6 is necessary to observe the
changes caused by this series. Hence, please wait until those patches
are picked up.

>>>> diff --git a/drivers/mfd/ti_am335x_tscadc.c b/drivers/mfd/ti_am335x_tscadc.c
>>>> index 467c80e1c4ae..e4e4b22eebc9 100644
>>>> --- a/drivers/mfd/ti_am335x_tscadc.c
>>>> +++ b/drivers/mfd/ti_am335x_tscadc.c
>>>> @@ -68,12 +68,6 @@ static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc)
>>>>  	DEFINE_WAIT(wait);
>>>>  	u32 reg;
>>>>  
>>>> -	/*
>>>> -	 * disable TSC steps so it does not run while the ADC is using it. If
>>>> -	 * write 0 while it is running (it just started or was already running)
>>>> -	 * then it completes all steps that were enabled and stops then.
>>>> -	 */
>>>> -	tscadc_writel(tsadc, REG_SE, 0);
>>>>  	reg = tscadc_readl(tsadc, REG_ADCFSM);
>>>>  	if (reg & SEQ_STATUS) {
>>>>  		tsadc->adc_waiting = true;
>>>> @@ -86,8 +80,12 @@ static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc)
>>>>  		spin_lock_irq(&tsadc->reg_lock);
>>>>  		finish_wait(&tsadc->reg_se_wait, &wait);
>>>>  
>>>> +		/*
>>>> +		 * Sequencer should either be idle or
>>>> +		 * busy applying the charge step.
>>>> +		 */
>>>>  		reg = tscadc_readl(tsadc, REG_ADCFSM);
>>>> -		WARN_ON(reg & SEQ_STATUS);
>>>> +		WARN_ON((reg & SEQ_STATUS) && !(reg & CHARGE_STEP));
>>>>  		tsadc->adc_waiting = false;
>>>>  	}
>>>>  	tsadc->adc_in_use = true;
>>>> @@ -96,7 +94,6 @@ static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc)
>>>>  void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val)
>>>>  {
>>>>  	spin_lock_irq(&tsadc->reg_lock);
>>>> -	tsadc->reg_se_cache |= val;
>>>>  	am335x_tscadc_need_adc(tsadc);
>>>>  
>>>>  	tscadc_writel(tsadc, REG_SE, val);
>>>> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
>>>> index 3f4e994ace2b..1fd50dcfe47c 100644
>>>> --- a/include/linux/mfd/ti_am335x_tscadc.h
>>>> +++ b/include/linux/mfd/ti_am335x_tscadc.h
>>>> @@ -128,6 +128,7 @@
>>>>  
>>>>  /* Sequencer Status */
>>>>  #define SEQ_STATUS BIT(5)
>>>> +#define CHARGE_STEP		0x11
>>>>  
>>>>  #define ADC_CLK			3000000
>>>>  #define TOTAL_STEPS		16
>>>
> 
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