Input: ads7846 - assorted updates

This updates the ads7846 touchscreen driver:
  - to allow faster clocking (this driver doesn't push sample rates);
  - bugfixes the conversion of spi_transfer to lists;
  - some dma-unsafe command buffers are fixed.

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

1 files changed, 44 insertions, 24 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 72cf0a26d676..8c12a974b411 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -48,10 +48,13 @@
 
 #define TS_POLL_PERIOD  msecs_to_jiffies(10)
 
+/* this driver doesn't aim at the peak continuous sample rate */
+#define SAMPLE_BITS     (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
+
 struct ts_event {
         /* For portability, we can't read 12 bit values using SPI (which
          * would make the controller deliver them as native byteorder u16
-         * with msbs zeroed).  Instead, we read them as two 8-byte values,
+         * with msbs zeroed).  Instead, we read them as two 8-bit values,
          * which need byteswapping then range adjustment.
          */
         __be16 x;
@@ -68,6 +71,7 @@ struct ads7846 {
         u16                     vref_delay_usecs;
         u16                     x_plate_ohms;
 
+        u8                      read_x, read_y, read_z1, read_z2;
         struct ts_event         tc;
 
         struct spi_transfer     xfer[8];
@@ -117,10 +121,10 @@ struct ads7846 {
 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
         | ADS_12_BIT | ADS_DFR)
 
-static const u8 read_y  = READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON;
-static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
-static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
-static const u8 read_x  = READ_12BIT_DFR(x)  | ADS_PD10_PDOWN;  /* LAST */
+#define READ_Y  (READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON)
+#define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
+#define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
+#define READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_PDOWN)   /* LAST */
 
 /* single-ended samples need to first power up reference voltage;
  * we leave both ADC and VREF powered
@@ -128,8 +132,8 @@ static const u8	read_x  = READ_12BIT_DFR(x)  | ADS_PD10_PDOWN;	/* LAST */
 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
         | ADS_12_BIT | ADS_SER)
 
-static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
-static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
+#define REF_ON  (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
+#define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
 
 /*--------------------------------------------------------------------------*/
 
@@ -138,7 +142,9 @@ static const u8	ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
  */
 
 struct ser_req {
+        u8                      ref_on;
         u8                      command;
+        u8                      ref_off;
         u16                     scratch;
         __be16                  sample;
         struct spi_message      msg;
@@ -160,7 +166,8 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
         INIT_LIST_HEAD(&req->msg.transfers);
 
         /* activate reference, so it has time to settle; */
-        req->xfer[0].tx_buf = &ref_on;
+        req->ref_on = REF_ON;
+        req->xfer[0].tx_buf = &req->ref_on;
         req->xfer[0].len = 1;
         req->xfer[1].rx_buf = &req->scratch;
         req->xfer[1].len = 2;
@@ -182,7 +189,8 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
         /* REVISIT:  take a few more samples, and compare ... */
 
         /* turn off reference */
-        req->xfer[4].tx_buf = &ref_off;
+        req->ref_off = REF_OFF;
+        req->xfer[4].tx_buf = &req->ref_off;
         req->xfer[4].len = 1;
         req->xfer[5].rx_buf = &req->scratch;
         req->xfer[5].len = 2;
@@ -400,7 +408,6 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         struct input_dev                *input_dev;
         struct ads7846_platform_data    *pdata = spi->dev.platform_data;
         struct spi_transfer             *x;
-        int                             i;
         int                             err;
 
         if (!spi->irq) {
@@ -414,9 +421,9 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         }
 
         /* don't exceed max specified sample rate */
-        if (spi->max_speed_hz > (125000 * 16)) {
+        if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
                 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
-                                (spi->max_speed_hz/16)/1000);
+                                (spi->max_speed_hz/SAMPLE_BITS)/1000);
                 return -EINVAL;
         }
 
@@ -469,45 +476,58 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         /* set up the transfers to read touchscreen state; this assumes we
          * use formula #2 for pressure, not #3.
          */
+        INIT_LIST_HEAD(&ts->msg.transfers);
         x = ts->xfer;
 
         /* y- still on; turn on only y+ (and ADC) */
-        x->tx_buf = &read_y;
+        ts->read_y = READ_Y;
+        x->tx_buf = &ts->read_y;
         x->len = 1;
+        spi_message_add_tail(x, &ts->msg);
+
         x++;
         x->rx_buf = &ts->tc.y;
         x->len = 2;
-        x++;
+        spi_message_add_tail(x, &ts->msg);
 
         /* turn y+ off, x- on; we'll use formula #2 */
         if (ts->model == 7846) {
-                x->tx_buf = &read_z1;
+                x++;
+                ts->read_z1 = READ_Z1;
+                x->tx_buf = &ts->read_z1;
                 x->len = 1;
+                spi_message_add_tail(x, &ts->msg);
+
                 x++;
                 x->rx_buf = &ts->tc.z1;
                 x->len = 2;
-                x++;
+                spi_message_add_tail(x, &ts->msg);
 
-                x->tx_buf = &read_z2;
+                x++;
+                ts->read_z2 = READ_Z2;
+                x->tx_buf = &ts->read_z2;
                 x->len = 1;
+                spi_message_add_tail(x, &ts->msg);
+
                 x++;
                 x->rx_buf = &ts->tc.z2;
                 x->len = 2;
-                x++;
+                spi_message_add_tail(x, &ts->msg);
         }
 
         /* turn y- off, x+ on, then leave in lowpower */
-        x->tx_buf = &read_x;
+        x++;
+        ts->read_x = READ_X;
+        x->tx_buf = &ts->read_x;
         x->len = 1;
+        spi_message_add_tail(x, &ts->msg);
+
         x++;
         x->rx_buf = &ts->tc.x;
         x->len = 2;
-        x++;
-
-        CS_CHANGE(x[-1]);
+        CS_CHANGE(*x);
+        spi_message_add_tail(x, &ts->msg);
 
-        for (i = 0; i < x - ts->xfer; i++)
-                spi_message_add_tail(&ts->xfer[i], &ts->msg);
         ts->msg.complete = ads7846_rx;
         ts->msg.context = ts;