[patch 2.6.27-rc6] ads7846: work better with DMA

[patch 2.6.27-rc6] ads7846: work better with DMA

[David Brownell]

From: David Brownell <dbrownell@users.sourceforge.net>

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) ... but no
mergeable patch addressed it.  Pending any more comprehensive fix,
just push the relevant data into cache lines that won't be shared,
preventing those issues (but not in a very pretty way).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
---
Please merge for 2.6.27-final (and forward to -stable for backports);
this lack-of-patch has lingered for way too long.

 drivers/input/touchscreen/ads7846.c |   24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -85,10 +85,6 @@ 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 spi_transfer	xfer[18];
 	struct spi_message	msg[5];
 	struct spi_message	*last_msg;
@@ -116,6 +112,26 @@ struct ads7846 {
 	void			*filter_data;
 	void			(*filter_cleanup)(void *data);
 	int			(*get_pendown_state)(void);
+
+	/* NOTE: this is a bit klugey.  Ideally all these I/O buffers
+	 * would be in a separate buffer (from the heap) to make DMA
+	 * work better.  Instead, we trust that starting them on their
+	 * own cache line, at the end of this struct, suffices to avoid
+	 * cacheline sharing issues -- pending any better fix.
+	 *
+	 * The first several systems to use this driver didn't use DMA
+	 * with SPI, at least for small I/O requests as used here, so
+	 * the cache line sharing issues wouldn't show up there.
+	 */
+	u8			read_x ____cacheline_aligned;
+	u8			read_y;
+	u8			read_z1:
+	u8			read_z2;
+	u8			pwrdown;
+	u16			dummy;		/* for the pwrdown read */
+
+	struct ts_event		tc;
+
 };
 
 /* leave chip selected when we're done, for quicker re-select? */

Re: [patch 2.6.27-rc6] ads7846: work better with DMA

[Dmitry Torokhov]

On Mon, Sep 15, 2008 at 04:32:17PM -0700, David Brownell wrote:
> From: David Brownell <dbrownell@users.sourceforge.net>
> 
> 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) ... but no
> mergeable patch addressed it.  Pending any more comprehensive fix,
> just push the relevant data into cache lines that won't be shared,
> preventing those issues (but not in a very pretty way).
> 

How about this one? Because the change is purely mechanical I feel
pretty safe about it...

-- 
Dmitry


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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

 drivers/input/touchscreen/ads7846.c |   87 +++++++++++++++++++++--------------
 1 files changed, 51 insertions(+), 36 deletions(-)


diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 6020a7d..b9b7fc6 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -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");

Re: [patch 2.6.27-rc6] ads7846: work better with DMA

[David Brownell]

On Tuesday 16 September 2008, Dmitry Torokhov wrote:
> On Mon, Sep 15, 2008 at 04:32:17PM -0700, David Brownell wrote:
> > From: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
> > 
> > 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) ... but no
> > mergeable patch addressed it.  Pending any more comprehensive fix,
> > just push the relevant data into cache lines that won't be shared,
> > preventing those issues (but not in a very pretty way).
> > 
> 
> How about this one? Because the change is purely mechanical I feel
> pretty safe about it...

Looks OK to me ... sorry for the delayed response.

Nicolas:  this may be useful on the at91sam926[03] EK boards.


> 
> -- 
> Dmitry
> 
> 
> 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: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
> Signed-off-by: Dmitry Torokhov <dtor-JGs/UdohzUI@public.gmane.org>
> ---
> 
>  drivers/input/touchscreen/ads7846.c |   87 +++++++++++++++++++++--------------
>  1 files changed, 51 insertions(+), 36 deletions(-)
> 
> 
> diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
> index 6020a7d..b9b7fc6 100644
> --- a/drivers/input/touchscreen/ads7846.c
> +++ b/drivers/input/touchscreen/ads7846.c
> @@ -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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