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    Subject[GIT PATCH 5/6] ads7846: assorted updates
    From: David Brownell <dbrownell@users.sourceforge.net>

    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>
    ---

    drivers/input/touchscreen/ads7846.c | 68 +++++++++++++++++++++++-------------
    1 files changed, 44 insertions(+), 24 deletions(-)

    Index: work/drivers/input/touchscreen/ads7846.c
    ===================================================================
    --- work.orig/drivers/input/touchscreen/ads7846.c
    +++ work/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
    #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
    */

    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 dev
    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 dev
    /* 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(struc
    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(struc
    }

    /* 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(struc
    /* 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;

    -
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