Patch "spi: omap2-mcspi: disable other channels CHCONF_FORCE in prepare_message" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
spi-omap2-mcspi-disable-other-channels-chconf_force-in-prepare_message.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Neil Armstrong <[email protected]>
Date: Fri, 9 Oct 2015 15:47:41 +0200
Subject: spi: omap2-mcspi: disable other channels CHCONF_FORCE in prepare_message

From: Neil Armstrong <[email protected]>

commit 468a32082b04c7febccfcd55b06ecbc438fcddcc upstream.

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.

---
 drivers/spi/spi-omap2-mcspi.c |   28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

@@ -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 plat
 	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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/spi-omap2-mcspi-disable-other-channels-chconf_force-in-prepare_message.patch