Patch "spi: omap2-mcspi: poll OMAP2_MCSPI_CHSTAT_RXS for PIO transfer" has been added to the 4.9-stable tree

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

spi: omap2-mcspi: poll OMAP2_MCSPI_CHSTAT_RXS for PIO transfer

to the 4.9-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-poll-omap2_mcspi_chstat_rxs-for-pio-transfer.patch
and it can be found in the queue-4.9 subdirectory.

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

From: Akinobu Mita <[email protected]>
Date: Wed, 22 Mar 2017 09:18:26 +0900
Subject: spi: omap2-mcspi: poll OMAP2_MCSPI_CHSTAT_RXS for PIO transfer

From: Akinobu Mita <[email protected]>

[ Upstream commit 812613591cb652344186c4cd912304ed02138566 ]

When running the spi-loopback-test with slower clock rate like 10 KHz, the test for 251 bytes transfer was failed. This failure triggered an spi-omap2-mcspi's error message "DMA RX last word empty".

This message means that PIO for reading the remaining bytes due to the DMA transfer length reduction is failed. This problem can be fixed by polling OMAP2_MCSPI_CHSTAT_RXS bit in channel status register to wait until the receive buffer register is filled.

---
 drivers/spi/spi-omap2-mcspi.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

@@ -454,6 +454,8 @@ omap2_mcspi_rx_dma(struct spi_device *sp
 	int			elements = 0;
 	int			word_len, element_count;
 	struct omap2_mcspi_cs	*cs = spi->controller_state;
+	void __iomem		*chstat_reg = cs->base + OMAP2_MCSPI_CHSTAT0;
+
 	mcspi = spi_master_get_devdata(spi->master);
 	mcspi_dma = &mcspi->dma_channels[spi->chip_select];
 	count = xfer->len;

@@ -549,8 +551,8 @@ omap2_mcspi_rx_dma(struct spi_device *sp
 	if (l & OMAP2_MCSPI_CHCONF_TURBO) {
 		elements--;
 
-		if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
-				   & OMAP2_MCSPI_CHSTAT_RXS)) {
+		if (!mcspi_wait_for_reg_bit(chstat_reg,
+					    OMAP2_MCSPI_CHSTAT_RXS)) {
 			u32 w;
 
 			w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);

@@ -568,8 +570,7 @@ omap2_mcspi_rx_dma(struct spi_device *sp
 			return count;
 		}
 	}
-	if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
-				& OMAP2_MCSPI_CHSTAT_RXS)) {
+	if (!mcspi_wait_for_reg_bit(chstat_reg, OMAP2_MCSPI_CHSTAT_RXS)) {
 		u32 w;
 
 		w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);

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

queue-4.9/spi-omap2-mcspi-poll-omap2_mcspi_chstat_rxs-for-pio-transfer.patch