Re: [PATCH 2/5] input: touchscreen: ti_am335x_tsc: Remove udelay in interrupt handler

[Lee Jones]

On Fri, 07 Nov 2014, Vignesh R wrote:

> From: Brad Griffis <bgriffis@xxxxxx>
> 
> 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.
> 
> Signed-off-by: Brad Griffis <bgriffis@xxxxxx>
> [vigneshr@xxxxxx: Ported the patch from v3.12 to v3.18rc2]
> 
> Signed-off-by: Vignesh R <vigneshr@xxxxxx>
> ---
>  drivers/input/touchscreen/ti_am335x_tsc.c | 56 ++++++++++++-------------------
>  include/linux/mfd/ti_am335x_tscadc.h      |  3 +-

Acked-by: Lee Jones <lee.jones@xxxxxxxxxx>

>  2 files changed, 24 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
> index 1aeac9675fe7..483fd97c0e0c 100644
> --- a/drivers/input/touchscreen/ti_am335x_tsc.c
> +++ b/drivers/input/touchscreen/ti_am335x_tsc.c
> @@ -173,11 +173,9 @@ static void titsc_step_config(struct titsc *ts_dev)
>  		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
>  	}
>  
> -	/* Charge step configuration */
> -	config = ts_dev->bit_xp | ts_dev->bit_yn |
> -			STEPCHARGE_RFP_XPUL | STEPCHARGE_RFM_XNUR |
> -			STEPCHARGE_INM_AN1 | STEPCHARGE_INP(ts_dev->inp_yp);
> +	/* Make CHARGECONFIG same as IDLECONFIG */
>  
> +	config = titsc_readl(ts_dev, REG_IDLECONFIG);
>  	titsc_writel(ts_dev, REG_CHARGECONFIG, config);
>  	titsc_writel(ts_dev, REG_CHARGEDELAY, CHARGEDLY_OPENDLY);
>  
> @@ -264,9 +262,26 @@ static irqreturn_t titsc_irq(int irq, void *dev)
>  	unsigned int status, irqclr = 0;
>  	unsigned int x = 0, y = 0;
>  	unsigned int z1, z2, z;
> -	unsigned int fsm;
>  
> -	status = titsc_readl(ts_dev, REG_IRQSTATUS);
> +	status = titsc_readl(ts_dev, REG_RAWIRQSTATUS);
> +	if (status & IRQENB_HW_PEN) {
> +		ts_dev->pen_down = true;
> +		titsc_writel(ts_dev, REG_IRQWAKEUP, 0x00);
> +		titsc_writel(ts_dev, REG_IRQCLR, IRQENB_HW_PEN);
> +		irqclr |= IRQENB_HW_PEN;
> +	}
> +
> +	if (status & IRQENB_PENUP) {
> +		ts_dev->pen_down = false;
> +		input_report_key(input_dev, BTN_TOUCH, 0);
> +		input_report_abs(input_dev, ABS_PRESSURE, 0);
> +		input_sync(input_dev);
> +		irqclr |= IRQENB_PENUP;
> +	}
> +
> +	if (status & IRQENB_EOS)
> +		irqclr |= IRQENB_EOS;
> +
>  	/*
>  	 * ADC and touchscreen share the IRQ line.
>  	 * FIFO1 interrupts are used by ADC. Handle FIFO0 IRQs here only
> @@ -297,34 +312,6 @@ static irqreturn_t titsc_irq(int irq, void *dev)
>  		}
>  		irqclr |= IRQENB_FIFO0THRES;
>  	}
> -
> -	/*
> -	 * Time for sequencer to settle, to read
> -	 * correct state of the sequencer.
> -	 */
> -	udelay(SEQ_SETTLE);
> -
> -	status = titsc_readl(ts_dev, REG_RAWIRQSTATUS);
> -	if (status & IRQENB_PENUP) {
> -		/* Pen up event */
> -		fsm = titsc_readl(ts_dev, REG_ADCFSM);
> -		if (fsm == ADCFSM_STEPID) {
> -			ts_dev->pen_down = false;
> -			input_report_key(input_dev, BTN_TOUCH, 0);
> -			input_report_abs(input_dev, ABS_PRESSURE, 0);
> -			input_sync(input_dev);
> -		} else {
> -			ts_dev->pen_down = true;
> -		}
> -		irqclr |= IRQENB_PENUP;
> -	}
> -
> -	if (status & IRQENB_HW_PEN) {
> -
> -		titsc_writel(ts_dev, REG_IRQWAKEUP, 0x00);
> -		titsc_writel(ts_dev, REG_IRQCLR, IRQENB_HW_PEN);
> -	}
> -
>  	if (irqclr) {
>  		titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
>  		am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
> @@ -417,6 +404,7 @@ static int titsc_probe(struct platform_device *pdev)
>  	}
>  
>  	titsc_writel(ts_dev, REG_IRQENABLE, IRQENB_FIFO0THRES);
> +	titsc_writel(ts_dev, REG_IRQENABLE, IRQENB_EOS);
>  	err = titsc_config_wires(ts_dev);
>  	if (err) {
>  		dev_err(&pdev->dev, "wrong i/p wire configuration\n");
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> index e2e70053470e..c99be5dc0f5c 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)

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/