Patch "spi: sh-msiof: Fix timeout failures for TX-only DMA transfers" has been added to the 4.14-stable tree

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

spi: sh-msiof: Fix timeout failures for TX-only DMA transfers

to the 4.14-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-sh-msiof-fix-timeout-failures-for-tx-only-dma-transfers.patch
and it can be found in the queue-4.14 subdirectory.

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

From: Geert Uytterhoeven <[email protected]>
Date: Wed, 3 Jan 2018 18:11:14 +0100
Subject: spi: sh-msiof: Fix timeout failures for TX-only DMA transfers

From: Geert Uytterhoeven <[email protected]>

[ Upstream commit 89434c3c35081439627baa2225622d5bd12242fe ]

When using RX (with or without TX), the DMA interrupt triggers completion when the RX FIFO has been emptied, i.e. after the full transfer has finished.

However, when using TX without RX, the DMA interrupt triggers completion as soon as the DMA engine has filled the TX FIFO, i.e. before the full transfer has finished. Then sh_msiof_modify_ctr_wait() will spin until the transfer has really finished and the TFSE bit is cleared, for at most 1 ms. For slow speeds and/or large transfers, this may cause timeouts and transfer failures:

spi_sh_msiof e6e10000.spi: failed to shut down hardware 74x164 spi2.0: SPI transfer failed: -110 spi_master spi2: failed to transfer one message from queue 74x164 spi2.0: Failed writing: -110

Fix this by waiting explicitly until the TX FIFO has been emptied.

Based on a patch in the BSP by Hiromitsu Yamasaki.

---
 drivers/spi/spi-sh-msiof.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

@@ -797,11 +797,21 @@ static int sh_msiof_dma_once(struct sh_m
 		goto stop_dma;
 	}
 
-	/* wait for tx fifo to be emptied / rx fifo to be filled */
+	/* wait for tx/rx DMA completion */
 	ret = sh_msiof_wait_for_completion(p);
 	if (ret)
 		goto stop_reset;
 
+	if (!rx) {
+		reinit_completion(&p->done);
+		sh_msiof_write(p, IER, IER_TEOFE);
+
+		/* wait for tx fifo to be emptied */
+		ret = sh_msiof_wait_for_completion(p);
+		if (ret)
+			goto stop_reset;
+	}
+
 	/* clear status bits */
 	sh_msiof_reset_str(p);
 

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

queue-4.14/acpi-ec-fix-debugfs_create_-usage.patch queue-4.14/spi-sh-msiof-fix-timeout-failures-for-tx-only-dma-transfers.patch