drivers: spi: ti-qspi: wait for busy bit clear before data write/read

Data corruption is seen while reading/writing large data from/to qspi
device because the data register is over written or read before data
is ready which is denoted by busy bit in status register. SO adding
a busy bit check before writing/reading data to/from qspi device.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c
index 884a716e50cb822ce49dcb0e925a2c1856130bcb..5c061687035886e5768bf6031616068906540b04 100644 (file)
--- a/drivers/spi/spi-ti-qspi.c
+++ b/drivers/spi/spi-ti-qspi.c
@@ -101,6 +101,7 @@ struct ti_qspi {
 #define QSPI_FLEN(n)                   ((n - 1) << 0)
 
 /* STATUS REGISTER */
+#define BUSY                           0x01
 #define WC                             0x02
 
 /* INTERRUPT REGISTER */
@@ -199,6 +200,21 @@ static void ti_qspi_restore_ctx(struct ti_qspi *qspi)
        ti_qspi_write(qspi, ctx_reg->clkctrl, QSPI_SPI_CLOCK_CNTRL_REG);
 }
 
+static inline u32 qspi_is_busy(struct ti_qspi *qspi)
+{
+       u32 stat;
+       unsigned long timeout = jiffies + QSPI_COMPLETION_TIMEOUT;
+
+       stat = ti_qspi_read(qspi, QSPI_SPI_STATUS_REG);
+       while ((stat & BUSY) && time_after(timeout, jiffies)) {
+               cpu_relax();
+               stat = ti_qspi_read(qspi, QSPI_SPI_STATUS_REG);
+       }
+
+       WARN(stat & BUSY, "qspi busy\n");
+       return stat & BUSY;
+}
+
 static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 {
        int wlen, count;
@@ -211,6 +227,9 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
        wlen = t->bits_per_word >> 3;   /* in bytes */
 
        while (count) {
+               if (qspi_is_busy(qspi))
+                       return -EBUSY;
+
                switch (wlen) {
                case 1:
                        dev_dbg(qspi->dev, "tx cmd %08x dc %08x data %02x\n",
@@ -266,6 +285,9 @@ static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 
        while (count) {
                dev_dbg(qspi->dev, "rx cmd %08x dc %08x\n", cmd, qspi->dc);
+               if (qspi_is_busy(qspi))
+                       return -EBUSY;
+
                ti_qspi_write(qspi, cmd, QSPI_SPI_CMD_REG);
                if (!wait_for_completion_timeout(&qspi->transfer_complete,
                                                 QSPI_COMPLETION_TIMEOUT)) {