Merge tag 'staging-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

Pull staging and IIO updates from Greg KH:
 "Here are the big staging/iio patches for 4.19-rc1.

  Lots of churn here, with tons of cleanups happening in staging
  drivers, a removal of an old crypto driver that no one was using
  (skein), and the addition of some new IIO drivers. Also added was a
  "gasket" driver from Google that needs loads of work and the erofs
  filesystem.

  Even with adding all of the new drivers and a new filesystem, we are
  only adding about 1000 lines overall to the kernel linecount, which
  shows just how much cleanup happened, and how big the unused crypto
  driver was.

  All of these have been in the linux-next tree for a while now with no
  reported issues"

* tag 'staging-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (903 commits)
  staging:rtl8192u: Remove unused macro definitions - Style
  staging:rtl8192u: Add spaces around '+' operator - Style
  staging:rtl8192u: Remove stale comment - Style
  staging: rtl8188eu: remove unused mp_custom_oid.h
  staging: fbtft: Add spaces around / - Style
  staging: fbtft: Erases some repetitive usage of function name - Style
  staging: fbtft: Adjust some empty-line problems - Style
  staging: fbtft: Removes one nesting level to help readability - Style
  staging: fbtft: Changes gamma table to define.
  staging: fbtft: A bit more information on dev_err.
  staging: fbtft: Fixes some alignment issues - Style
  staging: fbtft: Puts macro arguments in parenthesis to avoid precedence issues - Style
  staging: rtl8188eu: remove unused array dB_Invert_Table
  staging: rtl8188eu: remove whitespace, add missing blank line
  staging: rtl8188eu: use is_multicast_ether_addr in rtw_sta_mgt.c
  staging: rtl8188eu: remove whitespace - style
  staging: rtl8188eu: cleanup block comment - style
  staging: rtl8188eu: use is_multicast_ether_addr in rtl8188eu_xmit.c
  staging: rtl8188eu: use is_multicast_ether_addr in recv_linux.c
  staging: rtlwifi: refactor rtl_get_tcb_desc
  ...

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
index 9430b54121e0..36b59d8957fb 100644
--- a/drivers/iio/adc/hx711.c
+++ b/drivers/iio/adc/hx711.c
@@ -97,6 +97,14 @@ struct hx711_data {
 	 * 2x32-bit channel + 64-bit timestamp
 	 */
 	u32			buffer[4];
+	/*
+	 * delay after a rising edge on SCK until the data is ready DOUT
+	 * this is dependent on the hx711 where the datasheet tells a
+	 * maximum value of 100 ns
+	 * but also on potential parasitic capacities on the wiring
+	 */
+	u32			data_ready_delay_ns;
+	u32			clock_frequency;
 };
 
 static int hx711_cycle(struct hx711_data *hx711_data)
@@ -110,6 +118,14 @@ static int hx711_cycle(struct hx711_data *hx711_data)
 	 */
 	preempt_disable();
 	gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
+
+	/*
+	 * wait until DOUT is ready
+	 * it turned out that parasitic capacities are extending the time
+	 * until DOUT has reached it's value
+	 */
+	ndelay(hx711_data->data_ready_delay_ns);
+
 	val = gpiod_get_value(hx711_data->gpiod_dout);
 	/*
 	 * here we are not waiting for 0.2 us as suggested by the datasheet,
@@ -120,6 +136,12 @@ static int hx711_cycle(struct hx711_data *hx711_data)
 	gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
 	preempt_enable();
 
+	/*
+	 * make it a square wave for addressing cases with capacitance on
+	 * PC_SCK
+	 */
+	ndelay(hx711_data->data_ready_delay_ns);
+
 	return val;
 }
 
@@ -458,6 +480,7 @@ static const struct iio_chan_spec hx711_chan_spec[] = {
 static int hx711_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
 	struct hx711_data *hx711_data;
 	struct iio_dev *indio_dev;
 	int ret;
@@ -530,6 +553,22 @@ static int hx711_probe(struct platform_device *pdev)
 	hx711_data->gain_set = 128;
 	hx711_data->gain_chan_a = 128;
 
+	hx711_data->clock_frequency = 400000;
+	ret = of_property_read_u32(np, "clock-frequency",
+					&hx711_data->clock_frequency);
+
+	/*
+	 * datasheet says the high level of PD_SCK has a maximum duration
+	 * of 50 microseconds
+	 */
+	if (hx711_data->clock_frequency < 20000) {
+		dev_warn(dev, "clock-frequency too low - assuming 400 kHz\n");
+		hx711_data->clock_frequency = 400000;
+	}
+
+	hx711_data->data_ready_delay_ns =
+				1000000000 / hx711_data->clock_frequency;
+
 	platform_set_drvdata(pdev, indio_dev);
 
 	indio_dev->name = "hx711";