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

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Message-ID: <20150120160410.GL13701@x1>
Date:	Tue, 20 Jan 2015 16:04:10 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	"R, Vignesh" <vigneshr@...com>
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 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?

> >> 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
> > 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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