NFC: trf7970a: Clear possible spurious interrupt before transmitting

The trf7970a occasionally generates spurious interrupts
which can confuse the driver.  To help alleviate this,
clear any interrupts by reading the 'IRQ Status Register'
before starting a new transaction.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index b67946c18b40b7c984fb17a389fc42346a37b6a5..e7f22a44dc5298acdb98995c40638f8398414cb5 100644 (file)
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -1120,6 +1120,7 @@ static int trf7970a_in_send_cmd(struct nfc_digital_dev *ddev,
        char *prefix;
        unsigned int len;
        int ret;
+       u8 status;
 
        dev_dbg(trf->dev, "New request - state: %d, timeout: %d ms, len: %d\n",
                        trf->state, timeout, skb->len);
@@ -1195,6 +1196,11 @@ static int trf7970a_in_send_cmd(struct nfc_digital_dev *ddev,
 
        len = min_t(int, skb->len, TRF7970A_FIFO_SIZE);
 
+       /* Clear possible spurious interrupt */
+       ret = trf7970a_read_irqstatus(trf, &status);
+       if (ret)
+               goto out_err;
+
        ret = trf7970a_transmit(trf, skb, len);
        if (ret) {
                kfree_skb(trf->rx_skb);