patch "staging: comedi: mf6x4: Fix AI end-of-conversion detection" added to staging-next

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

staging: comedi: mf6x4: Fix AI end-of-conversion detection

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From 56c90457ebfe9422496aac6ef3d3f0f0ea8b2ec2 Mon Sep 17 00:00:00 2001
From: Ian Abbott <[email protected]>
Date: Mon, 7 Dec 2020 14:58:06 +0000
Subject: staging: comedi: mf6x4: Fix AI end-of-conversion detection

I have had reports from two different people that attempts to read the analog input channels of the MF624 board fail with an ETIMEDOUT error.

After triggering the conversion, the code calls comedi_timeout() with mf6x4_ai_eoc() as the callback function to check if the conversion is complete. The callback returns 0 if complete or -EBUSY if not yet complete. comedi_timeout() returns -ETIMEDOUT if it has not completed within a timeout period which is propagated as an error to the user application.

The existing code considers the conversion to be complete when the EOLC bit is high. However, according to the user manuals for the MF624 and MF634 boards, this test is incorrect because EOLC is an active low signal that goes high when the conversion is triggered, and goes low when the conversion is complete. Fix the problem by inverting the test of the EOLC bit state.

---
 drivers/staging/comedi/drivers/mf6x4.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index ea430237efa7..9da8dd748078 100644
@@ -112,8 +112,9 @@ static int mf6x4_ai_eoc(struct comedi_device *dev,
 	struct mf6x4_private *devpriv = dev->private;
 	unsigned int status;
 
+	/* EOLC goes low at end of conversion. */
 	status = ioread32(devpriv->gpioc_reg);
-	if (status & MF6X4_GPIOC_EOLC)
+	if ((status & MF6X4_GPIOC_EOLC) == 0)
 		return 0;
 	return -EBUSY;
 }

2.29.2