Re: [PATCH 2/4] input: touchscreen: ti_am335x_tsc: Remove udelay in interrupt handler

From: Vignesh R <vigneshr@ti.com>
To: Lee Jones <lee.jones@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	Benoit Cousson <bcousson@baylibre.com>,
	Tony Lindgren <tony@atomide.com>,
	Russell King <linux@arm.linux.org.uk>,
	Jonathan Cameron <jic23@kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald <pmeerw@pmeerw.net>,
	Samuel Ortiz <sameo@linux.intel.com>, Felipe Balbi <balbi@ti.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Jan Kardell <jan.kardell@telliq.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	Brad Griffis <bgriffis@ti.com>, <devicetree@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linux-omap@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-iio@vger.kernel.org>, <linux-input@vger.kernel.org>
Subject: Re: [PATCH 2/4] input: touchscreen: ti_am335x_tsc: Remove udelay in interrupt handler
Date: Fri, 7 Nov 2014 11:18:29 +0530	[thread overview]
Message-ID: <545C5D2D.9050406@ti.com> (raw)
In-Reply-To: <20141103150526.GI4538@x1>

On Monday 03 November 2014 08:35 PM, Lee Jones wrote:
> On Mon, 27 Oct 2014, Vignesh R wrote:
>> From: Brad Griffis <bgriffis@ti.com>
>>
>> TSC interrupt handler had udelay to avoid reporting of false pen-up
>> interrupt to user space. This patch implements workaround suggesting in
>> Advisory 1.0.31 of silicon errata for am335x, thus eliminating udelay
>> and touchscreen lag. This also improves performance of touchscreen and
>> eliminates sudden jump of cursor at touch release.
>>
>> IDLECONFIG and CHARGECONFIG registers are to be configured
>> with same values in order to eliminate false pen-up events. This
>> workaround may result in false pen-down to be detected, hence considerable
>> charge step delay needs to be added. The charge delay is set to 0xB000
>> (in terms of ADC clock cycles) by default.
>>
>> TSC steps are disabled at the end of every sampling cycle and EOS bit is
>> set. Once the EOS bit is set, the TSC steps need to be re-enabled to begin
>> next sampling cycle.
>>
>> 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.
>>
>> Signed-off-by: Brad Griffis <bgriffis@ti.com>
>> [vigneshr@ti.com: Ported patch from v3.12 to v3.18rc2]
>> Signed-off-by: Vignesh R <vigneshr@ti.com>
>> ---
>>  drivers/input/touchscreen/ti_am335x_tsc.c | 56 ++++++++++++-------------------
>>  drivers/mfd/ti_am335x_tscadc.c            |  7 ++--
>>  include/linux/mfd/ti_am335x_tscadc.h      |  4 ++-
>>  3 files changed, 30 insertions(+), 37 deletions(-)
> 
> [...]
> 
>> diff --git a/drivers/mfd/ti_am335x_tscadc.c b/drivers/mfd/ti_am335x_tscadc.c
>> index d877e777cce6..94ef8992f46b 100644
>> --- a/drivers/mfd/ti_am335x_tscadc.c
>> +++ b/drivers/mfd/ti_am335x_tscadc.c
>> @@ -86,8 +86,12 @@ 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 & (!CHARGE_STEP));
>>  		tsadc->adc_waiting = false;
>>  	}
>>  	tsadc->adc_in_use = true;
>> @@ -96,7 +100,6 @@ 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);
> 
> I believe all of these changes can, and therefor should live in a
> separate patch.

I will split this patch accordingly.

> 
>> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
>> index e2e70053470e..fcce182e4a35 100644
>> --- a/include/linux/mfd/ti_am335x_tscadc.h
>> +++ b/include/linux/mfd/ti_am335x_tscadc.h
>> @@ -52,6 +52,7 @@
>>  
>>  /* IRQ enable */
>>  #define IRQENB_HW_PEN		BIT(0)
>> +#define IRQENB_EOS		BIT(1)
>>  #define IRQENB_FIFO0THRES	BIT(2)
>>  #define IRQENB_FIFO0OVRRUN	BIT(3)
>>  #define IRQENB_FIFO0UNDRFLW	BIT(4)
>> @@ -107,7 +108,7 @@
>>  /* Charge delay */
>>  #define CHARGEDLY_OPEN_MASK	(0x3FFFF << 0)
>>  #define CHARGEDLY_OPEN(val)	((val) << 0)
>> -#define CHARGEDLY_OPENDLY	CHARGEDLY_OPEN(1)
>> +#define CHARGEDLY_OPENDLY	CHARGEDLY_OPEN(0xB000)
>>  
>>  /* Control register */
>>  #define CNTRLREG_TSCSSENB	BIT(0)
>> @@ -127,6 +128,7 @@
>>  
>>  /* Sequencer Status */
>>  #define SEQ_STATUS BIT(5)
>> +#define CHARGE_STEP		0x11
>>  
>>  #define ADC_CLK			3000000
>>  #define TOTAL_STEPS		16
> 
> The header changes should be split between the two Input and MFD
> patches.
> 