spi: stm32-qspi: Always wait BUSY bit to be cleared in stm32_qspi_wait_cmd()

BugLink: https://bugs.launchpad.net/bugs/1934179
[ Upstream commit d38fa9a155b2829b7e2cfcf8a4171b6dd3672808 ]

In U-boot side, an issue has been encountered when QSPI source clock is
running at low frequency (24 MHz for example), waiting for TCF bit to be
set didn't ensure that all data has been send out the FIFO, we should also
wait that BUSY bit is cleared.

To prevent similar issue in kernel driver, we implement similar behavior
by always waiting BUSY bit to be cleared.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20210603073421.8441-1-patrice.chotard@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/spi/spi-stm32-qspi.c b/drivers/spi/spi-stm32-qspi.c
index 4e726929bb4f5e90d161d3933aa6075e6aff260f..ea77d915216a201770dfb09e5c58e721ddaae142 100644 (file)
--- a/drivers/spi/spi-stm32-qspi.c
+++ b/drivers/spi/spi-stm32-qspi.c
@@ -291,7 +291,7 @@ static int stm32_qspi_wait_cmd(struct stm32_qspi *qspi,
        int err = 0;
 
        if (!op->data.nbytes)
-               return stm32_qspi_wait_nobusy(qspi);
+               goto wait_nobusy;
 
        if (readl_relaxed(qspi->io_base + QSPI_SR) & SR_TCF)
                goto out;
@@ -312,6 +312,9 @@ static int stm32_qspi_wait_cmd(struct stm32_qspi *qspi,
 out:
        /* clear flags */
        writel_relaxed(FCR_CTCF | FCR_CTEF, qspi->io_base + QSPI_FCR);
+wait_nobusy:
+       if (!err)
+               err = stm32_qspi_wait_nobusy(qspi);
 
        return err;
 }