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>

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c
index 884a716e50cb..5c0616870358 100644
--- 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)) {