linux-kernel - [PATCH 06/10] iio: adc: at91-sama5d2_adc: handle unfinished conversions

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Date:   Wed, 18 Dec 2019 16:24:01 +0000
From:   <Eugen.Hristev@...rochip.com>
To:     <jic23@...nel.org>, <robh+dt@...nel.org>,
        <alexandre.belloni@...tlin.com>
CC:     <Nicolas.Ferre@...rochip.com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-rtc@...r.kernel.org>,
        <a.zummo@...ertech.it>, <Ludovic.Desroches@...rochip.com>,
        <Eugen.Hristev@...rochip.com>
Subject: [PATCH 06/10] iio: adc: at91-sama5d2_adc: handle unfinished
 conversions

From: Eugen Hristev <eugen.hristev@...rochip.com>

It can happen that on IRQ trigger, not all conversions are done if
we are enabling multiple channels.
The IRQ is triggered on first EOC (end of channel), but it can happen
that not all channels are done. This leads into erroneous reports to
userspace (zero values or previous values).
To solve this, in trigger handler, check if the mask of done channels
is the same as the mask of active scan channels.
If it's the same, proceed and push to buffers. Otherwise, to avoid sleeping
in trigger handler, start a workq that will wait until all channels are
ready.
Normally, it should happen that in a short time fashion, all channels are
ready, since the first IRQ triggered.
The workq can stall in a loop if a hardware fault happens (for example
the clock suddently dissappears), but if it's a hardware fault then
even exiting the workq won't fix the hardware.

Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index c575970..a6b4dff 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -8,6 +8,7 @@
 
 #include <linux/bitops.h>
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/interrupt.h>
@@ -487,6 +488,21 @@ static inline int at91_adc_of_xlate(struct iio_dev *indio_dev,
 	return at91_adc_chan_xlate(indio_dev, iiospec->args[0]);
 }
 
+static unsigned int at91_adc_active_scan_mask_to_reg(struct iio_dev *indio_dev)
+{
+	u32 mask = 0;
+	u8 bit;
+
+	for_each_set_bit(bit, indio_dev->active_scan_mask,
+			 indio_dev->num_channels) {
+		struct iio_chan_spec const *chan =
+			 at91_adc_chan_get(indio_dev, bit);
+		mask |= BIT(chan->channel);
+	}
+
+	return mask & GENMASK(11, 0);
+}
+
 static void at91_adc_config_emr(struct at91_adc_state *st)
 {
 	/* configure the extended mode register */
@@ -1044,12 +1060,13 @@ static int at91_adc_trigger_handler_nodma(struct iio_dev *indio_dev,
 					  struct iio_poll_func *pf)
 {
 	struct at91_adc_state *st = iio_priv(indio_dev);
+	u32 mask = at91_adc_active_scan_mask_to_reg(indio_dev);
 
 	/*
 	 * Check if the conversion is ready. If not, schedule a work to
 	 * check again later.
 	 */
-	if (!(at91_adc_readl(st, AT91_SAMA5D2_ISR) & GENMASK(11, 0))) {
+	if ((at91_adc_readl(st, AT91_SAMA5D2_ISR) & mask) != mask) {
 		schedule_work(&st->workq);
 		return -EINPROGRESS;
 	}
@@ -1269,9 +1286,13 @@ static void at91_adc_workq_handler(struct work_struct *workq)
 	struct at91_adc_state *st = container_of(workq,
 					struct at91_adc_state, workq);
 	struct iio_dev *indio_dev = iio_priv_to_dev(st);
+	u32 mask = at91_adc_active_scan_mask_to_reg(indio_dev);
 
 	if ((indio_dev->currentmode & INDIO_ALL_TRIGGERED_MODES) &&
 	    iio_trigger_validate_own_device(indio_dev->trig, indio_dev)) {
+		while ((at91_adc_readl(st, AT91_SAMA5D2_ISR) & mask) != mask)
+			udelay(1);
+
 		at91_adc_read_and_push_channels(indio_dev, st->timestamp);
 		iio_trigger_notify_done(indio_dev->trig);
 	} else {
-- 
2.7.4