Commit e8f462d2 authored by Dmitry Torokhov's avatar Dmitry Torokhov
Browse files

Input: ads7846 - fix cache line sharing issue 



We had a report a while back that the ads7846 driver had some issues
when used with DMA-based SPI controllers (like atmel_spi) on systems
where main memory is not DMA-coherent (most non-x86 boards). Allocate
memory potentially used for DMA separately to avoid cache line issues.

Reported-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent 2d517cab

drivers/input/touchscreen/ads7846.c

+51 −36
Original line number Diff line number Diff line
@@ -69,6 +69,17 @@ struct ts_event { 
	int	ignore;

};



/*

 * We allocate this separately to avoid cache line sharing issues when

 * driver is used with DMA-based SPI controllers (like atmel_spi) on

 * systems where main memory is not DMA-coherent (most non-x86 boards).

 */

struct ads7846_packet {

	u8			read_x, read_y, read_z1, read_z2, pwrdown;

	u16			dummy;		/* for the pwrdown read */

	struct ts_event		tc;

};



struct ads7846 {

	struct input_dev	*input;

	char			phys[32];
@@ -86,9 +97,7 @@ struct ads7846 { 
	u16			x_plate_ohms;

	u16			pressure_max;



	u8			read_x, read_y, read_z1, read_z2, pwrdown;

	u16			dummy;		/* for the pwrdown read */

	struct ts_event		tc;

	struct ads7846_packet	*packet;



	struct spi_transfer	xfer[18];

	struct spi_message	msg[5];
@@ -513,16 +522,17 @@ static int get_pendown_state(struct ads7846 *ts) 
static void ads7846_rx(void *ads)

{

	struct ads7846		*ts = ads;

	struct ads7846_packet	*packet = ts->packet;

	unsigned		Rt;

	u16			x, y, z1, z2;



	/* ads7846_rx_val() did in-place conversion (including byteswap) from

	 * on-the-wire format as part of debouncing to get stable readings.

	 */

	x = ts->tc.x;

	y = ts->tc.y;

	z1 = ts->tc.z1;

	z2 = ts->tc.z2;

	x = packet->tc.x;

	y = packet->tc.y;

	z1 = packet->tc.z1;

	z2 = packet->tc.z2;



	/* range filtering */

	if (x == MAX_12BIT)
@@ -546,10 +556,10 @@ static void ads7846_rx(void *ads) 
	 * the maximum. Don't report it to user space, repeat at least

	 * once more the measurement

	 */

	if (ts->tc.ignore || Rt > ts->pressure_max) {

	if (packet->tc.ignore || Rt > ts->pressure_max) {

#ifdef VERBOSE

		pr_debug("%s: ignored %d pressure %d\n",

			ts->spi->dev.bus_id, ts->tc.ignore, Rt);

			ts->spi->dev.bus_id, packet->tc.ignore, Rt);

#endif

		hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),

			      HRTIMER_MODE_REL);
@@ -642,6 +652,7 @@ static int ads7846_no_filter(void *ads, int data_idx, int *val) 
static void ads7846_rx_val(void *ads)

{

	struct ads7846 *ts = ads;

	struct ads7846_packet *packet = ts->packet;

	struct spi_message *m;

	struct spi_transfer *t;

	int val;
@@ -661,7 +672,7 @@ static void ads7846_rx_val(void *ads) 
	case ADS7846_FILTER_REPEAT:

		break;

	case ADS7846_FILTER_IGNORE:

		ts->tc.ignore = 1;

		packet->tc.ignore = 1;

		/* Last message will contain ads7846_rx() as the

		 * completion function.

		 */
@@ -669,7 +680,7 @@ static void ads7846_rx_val(void *ads) 
		break;

	case ADS7846_FILTER_OK:

		*(u16 *)t->rx_buf = val;

		ts->tc.ignore = 0;

		packet->tc.ignore = 0;

		m = &ts->msg[++ts->msg_idx];

		break;

	default:
@@ -774,7 +785,6 @@ static void ads7846_disable(struct ads7846 *ts) 
	/* we know the chip's in lowpower mode since we always

	 * leave it that way after every request

	 */



}



/* Must be called with ts->lock held */
@@ -850,6 +860,7 @@ static int __devinit setup_pendown(struct spi_device *spi, struct ads7846 *ts) 
static int __devinit ads7846_probe(struct spi_device *spi)

{

	struct ads7846			*ts;

	struct ads7846_packet		*packet;

	struct input_dev		*input_dev;

	struct ads7846_platform_data	*pdata = spi->dev.platform_data;

	struct spi_message		*m;
@@ -885,14 +896,16 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		return err;



	ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);

	packet = kzalloc(sizeof(struct ads7846_packet), GFP_KERNEL);

	input_dev = input_allocate_device();

	if (!ts || !input_dev) {

	if (!ts || !packet || !input_dev) {

		err = -ENOMEM;

		goto err_free_mem;

	}



	dev_set_drvdata(&spi->dev, ts);



	ts->packet = packet;

	ts->spi = spi;

	ts->input = input_dev;

	ts->vref_mv = pdata->vref_mv;
@@ -964,13 +977,13 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	spi_message_init(m);



	/* y- still on; turn on only y+ (and ADC) */

	ts->read_y = READ_Y(vref);

	x->tx_buf = &ts->read_y;

	packet->read_y = READ_Y(vref);

	x->tx_buf = &packet->read_y;

	x->len = 1;

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->tc.y;

	x->rx_buf = &packet->tc.y;

	x->len = 2;

	spi_message_add_tail(x, m);
@@ -982,12 +995,12 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		x->delay_usecs = pdata->settle_delay_usecs;



		x++;

		x->tx_buf = &ts->read_y;

		x->tx_buf = &packet->read_y;

		x->len = 1;

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.y;

		x->rx_buf = &packet->tc.y;

		x->len = 2;

		spi_message_add_tail(x, m);

	}
@@ -1000,13 +1013,13 @@ static int __devinit ads7846_probe(struct spi_device *spi) 


	/* turn y- off, x+ on, then leave in lowpower */

	x++;

	ts->read_x = READ_X(vref);

	x->tx_buf = &ts->read_x;

	packet->read_x = READ_X(vref);

	x->tx_buf = &packet->read_x;

	x->len = 1;

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->tc.x;

	x->rx_buf = &packet->tc.x;

	x->len = 2;

	spi_message_add_tail(x, m);
@@ -1015,12 +1028,12 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		x->delay_usecs = pdata->settle_delay_usecs;



		x++;

		x->tx_buf = &ts->read_x;

		x->tx_buf = &packet->read_x;

		x->len = 1;

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.x;

		x->rx_buf = &packet->tc.x;

		x->len = 2;

		spi_message_add_tail(x, m);

	}
@@ -1034,13 +1047,13 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		spi_message_init(m);



		x++;

		ts->read_z1 = READ_Z1(vref);

		x->tx_buf = &ts->read_z1;

		packet->read_z1 = READ_Z1(vref);

		x->tx_buf = &packet->read_z1;

		x->len = 1;

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.z1;

		x->rx_buf = &packet->tc.z1;

		x->len = 2;

		spi_message_add_tail(x, m);
@@ -1049,12 +1062,12 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
			x->delay_usecs = pdata->settle_delay_usecs;



			x++;

			x->tx_buf = &ts->read_z1;

			x->tx_buf = &packet->read_z1;

			x->len = 1;

			spi_message_add_tail(x, m);



			x++;

			x->rx_buf = &ts->tc.z1;

			x->rx_buf = &packet->tc.z1;

			x->len = 2;

			spi_message_add_tail(x, m);

		}
@@ -1066,13 +1079,13 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		spi_message_init(m);



		x++;

		ts->read_z2 = READ_Z2(vref);

		x->tx_buf = &ts->read_z2;

		packet->read_z2 = READ_Z2(vref);

		x->tx_buf = &packet->read_z2;

		x->len = 1;

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.z2;

		x->rx_buf = &packet->tc.z2;

		x->len = 2;

		spi_message_add_tail(x, m);
@@ -1081,12 +1094,12 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
			x->delay_usecs = pdata->settle_delay_usecs;



			x++;

			x->tx_buf = &ts->read_z2;

			x->tx_buf = &packet->read_z2;

			x->len = 1;

			spi_message_add_tail(x, m);



			x++;

			x->rx_buf = &ts->tc.z2;

			x->rx_buf = &packet->tc.z2;

			x->len = 2;

			spi_message_add_tail(x, m);

		}
@@ -1100,13 +1113,13 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	spi_message_init(m);



	x++;

	ts->pwrdown = PWRDOWN;

	x->tx_buf = &ts->pwrdown;

	packet->pwrdown = PWRDOWN;

	x->tx_buf = &packet->pwrdown;

	x->len = 1;

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->dummy;

	x->rx_buf = &packet->dummy;

	x->len = 2;

	CS_CHANGE(*x);

	spi_message_add_tail(x, m);
@@ -1159,6 +1172,7 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		ts->filter_cleanup(ts->filter_data);

 err_free_mem:

	input_free_device(input_dev);

	kfree(packet);

	kfree(ts);

	return err;

}
@@ -1184,6 +1198,7 @@ static int __devexit ads7846_remove(struct spi_device *spi) 
	if (ts->filter_cleanup)

		ts->filter_cleanup(ts->filter_data);



	kfree(ts->packet);

	kfree(ts);



	dev_dbg(&spi->dev, "unregistered touchscreen\n");

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