linux-kernel - Re: [PATCH 1/4] input: ti_am335x_tsc: correct step mask update after IRQ

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Message-ID: <20130816085350.GA26895@linutronix.de>
Date:	Fri, 16 Aug 2013 10:53:50 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Zubair Lutfullah <zubair.lutfullah@...il.com>
Cc:	jic23@....ac.uk, dmitry.torokhov@...il.com, sameo@...ux.intel.com,
	lee.jones@...aro.org, linux-iio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, Russ.Dill@...com
Subject: Re: [PATCH 1/4] input: ti_am335x_tsc: correct step mask update
 after IRQ

* Zubair Lutfullah | 2013-08-13 17:48:16 [+0100]:

>diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
>index e1c5300..e165fcb 100644
>--- a/drivers/input/touchscreen/ti_am335x_tsc.c
>+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
>@@ -52,6 +52,7 @@ struct titsc {
> 	u32			config_inp[4];
> 	u32			bit_xp, bit_xn, bit_yp, bit_yn;
> 	u32			inp_xp, inp_xn, inp_yp, inp_yn;
>+	u32			step_mask;
> };
> 
> static unsigned int titsc_readl(struct titsc *ts, unsigned int reg)
>@@ -196,7 +197,8 @@ static void titsc_step_config(struct titsc *ts_dev)
> 
> 	/* The steps1 … end and bit 0 for TS_Charge */
> 	stepenable = (1 << (end_step + 2)) - 1;
>-	am335x_tsc_se_set(ts_dev->mfd_tscadc, stepenable);
>+	ts_dev->step_mask = stepenable;
>+	am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> }
> 
> static void titsc_read_coordinates(struct titsc *ts_dev,
>@@ -316,7 +318,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)
> 
> 	if (irqclr) {
> 		titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
>-		am335x_tsc_se_update(ts_dev->mfd_tscadc);
>+		am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> 		return IRQ_HANDLED;
> 	}
> 	return IRQ_NONE;

titsc_step_config() computes the mask once since it does not change. It
is then assigned via am335x_tsc_se_set() to ->reg_se_cache() and later
always udpated via am335x_tsc_se_update(). This should ensure that ADC's
and TSC's bits are in sync and clear each other out.
Now you call am335x_tsc_se_set() in every irq which adds the TSC's mask
to ->reg_se_cache but why? It was never removed.

Sebastian
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