patch "iio: xilinx-xadc: Fix sequencer configuration for aux channels in" added to staging-linus

[<gregkh@linuxfoundation.org>]

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

    iio: xilinx-xadc: Fix sequencer configuration for aux channels in

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-linus 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 hopefully also be merged in Linus's tree for the
next -rc kernel release.

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


From 8bef455c8b1694547ee59e8b1939205ed9d901a6 Mon Sep 17 00:00:00 2001
From: Lars-Peter Clausen <lars@metafoo.de>
Date: Fri, 3 Apr 2020 15:27:15 +0200
Subject: iio: xilinx-xadc: Fix sequencer configuration for aux channels in
 simultaneous mode

The XADC has two internal ADCs. Depending on the mode it is operating in
either one or both of them are used. The device manual calls this
continuous (one ADC) and simultaneous (both ADCs) mode.

The meaning of the sequencing register for the aux channels changes
depending on the mode.

In continuous mode each bit corresponds to one of the 16 aux channels. And
the single ADC will convert them one by one in order.

In simultaneous mode the aux channels are split into two groups the first 8
channels are assigned to the first ADC and the other 8 channels to the
second ADC. The upper 8 bits of the sequencing register are unused and the
lower 8 bits control both ADCs. This means a bit needs to be set if either
the corresponding channel from the first group or the second group (or
both) are set.

Currently the driver does not have the special handling required for
simultaneous mode. Add it.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Fixes: bdc8cda1d010 ("iio:adc: Add Xilinx XADC driver")
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/adc/xilinx-xadc-core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
index 62ded9683a57..1aeaeafce589 100644
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -798,6 +798,16 @@ static int xadc_preenable(struct iio_dev *indio_dev)
 	if (ret)
 		goto err;
 
+	/*
+	 * In simultaneous mode the upper and lower aux channels are samples at
+	 * the same time. In this mode the upper 8 bits in the sequencer
+	 * register are don't care and the lower 8 bits control two channels
+	 * each. As such we must set the bit if either the channel in the lower
+	 * group or the upper group is enabled.
+	 */
+	if (seq_mode == XADC_CONF1_SEQ_SIMULTANEOUS)
+		scan_mask = ((scan_mask >> 8) | scan_mask) & 0xff0000;
+
 	ret = xadc_write_adc_reg(xadc, XADC_REG_SEQ(1), scan_mask >> 16);
 	if (ret)
 		goto err;
-- 
2.26.1