spi: omap2-mcspi: disable other channels CHCONF_FORCE in prepare_message

Since the "Switch driver to use transfer_one" change, the cs_change
behavior has changed and a channel chip select can still be
asserted when changing channel from a previous last transfer in a
message having the cs_change attribute.

Since there is no sense having multiple chip select being asserted at the
same time, disable all the remaining forced chip selects in a the
prepare_message called right before a spi_transfer_one_message call.
It ignores the current channel configuration in order to keep the
possibility to leave the chip select asserted between messages.

It fixes this bug on a DM8168 SoC ES2.1 Soc and an OMAP4 ES2.1 SoC.
It was hanging all the other channels transfers when a CHCONF_FORCE
is present on the wrong channel.

Fixes: b28cb9414db9 ("spi: omap2-mcspi: Switch driver to use transfer_one")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 3d09e0b69b73..1f8903d356e5 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -1217,6 +1217,33 @@ out:
         return status;
 }
 
+static int omap2_mcspi_prepare_message(struct spi_master *master,
+                                       struct spi_message *msg)
+{
+        struct omap2_mcspi      *mcspi = spi_master_get_devdata(master);
+        struct omap2_mcspi_regs *ctx = &mcspi->ctx;
+        struct omap2_mcspi_cs   *cs;
+
+        /* Only a single channel can have the FORCE bit enabled
+         * in its chconf0 register.
+         * Scan all channels and disable them except the current one.
+         * A FORCE can remain from a last transfer having cs_change enabled
+         */
+        list_for_each_entry(cs, &ctx->cs, node) {
+                if (msg->spi->controller_state == cs)
+                        continue;
+
+                if ((cs->chconf0 & OMAP2_MCSPI_CHCONF_FORCE)) {
+                        cs->chconf0 &= ~OMAP2_MCSPI_CHCONF_FORCE;
+                        writel_relaxed(cs->chconf0,
+                                        cs->base + OMAP2_MCSPI_CHCONF0);
+                        readl_relaxed(cs->base + OMAP2_MCSPI_CHCONF0);
+                }
+        }
+
+        return 0;
+}
+
 static int omap2_mcspi_transfer_one(struct spi_master *master,
                 struct spi_device *spi, struct spi_transfer *t)
 {
@@ -1344,6 +1371,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
         master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
         master->setup = omap2_mcspi_setup;
         master->auto_runtime_pm = true;
+        master->prepare_message = omap2_mcspi_prepare_message;
         master->transfer_one = omap2_mcspi_transfer_one;
         master->set_cs = omap2_mcspi_set_cs;
         master->cleanup = omap2_mcspi_cleanup;