Input: ti_am335x_tsc - replace delta filtering with median filtering

Previously, delta filtering was applied TSC co-ordinate readouts before reporting a single value to user space. This patch replaces delta filtering with median filtering. Median filtering sorts co-ordinate readouts, drops min and max values, and reports the average of remaining values. This method is more sensible than delta filtering. Median filtering is applied only if number of readouts is greater than 3 else just average of co-ordinate readouts is reported. Signed-off-by: Vignesh R <vigneshr@ti.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>

Input: ti_am335x_tsc - replace delta filtering with median filtering
Previously, delta filtering was applied TSC co-ordinate readouts before reporting a single value to user space. This patch replaces delta filtering with median filtering. Median filtering sorts co-ordinate readouts, drops min and max values, and reports the average of remaining values. This method is more sensible than delta filtering. Median filtering is applied only if number of readouts is greater than 3 else just average of co-ordinate readouts is reported. Signed-off-by: Vignesh R <vigneshr@ti.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Vignesh R · Jacob Stiffler
1 parent 88f7cc4b04
Showing 1 changed file with 52 additions and 40 deletions Side-by-side Diff
drivers/input/touchscreen/ti_am335x_tsc.c
@@ -26,6 +26,7 @@
 #include <linux/delay.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/sort.h>
  
 #include <linux/mfd/ti_am335x_tscadc.h>
  
  
  
  
  
  
  
  
  
@@ -204,56 +205,61 @@
 	am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
 }
  
+static int titsc_cmp_coord(const void *a, const void *b)
+{
+	return *(int *)a - *(int *)b;
+}
+
 static void titsc_read_coordinates(struct titsc *ts_dev,
 		u32 *x, u32 *y, u32 *z1, u32 *z2)
 {
-	unsigned int fifocount = titsc_readl(ts_dev, REG_FIFO0CNT);
-	unsigned int prev_val_x = ~0, prev_val_y = ~0;
-	unsigned int prev_diff_x = ~0, prev_diff_y = ~0;
-	unsigned int read, diff;
-	unsigned int i, channel;
+	unsigned int yvals[7], xvals[7];
+	unsigned int i, xsum = 0, ysum = 0;
 	unsigned int creads = ts_dev->coordinate_readouts;
-	unsigned int first_step = TOTAL_STEPS - (creads * 2 + 2);
  
-	*z1 = *z2 = 0;
-	if (fifocount % (creads * 2 + 2))
-		fifocount -= fifocount % (creads * 2 + 2);
-	/*
-	 * Delta filter is used to remove large variations in sampled
-	 * values from ADC. The filter tries to predict where the next
-	 * coordinate could be. This is done by taking a previous
-	 * coordinate and subtracting it form current one. Further the
-	 * algorithm compares the difference with that of a present value,
-	 * if true the value is reported to the sub system.
-	 */
-	for (i = 0; i < fifocount; i++) {
-		read = titsc_readl(ts_dev, REG_FIFO0);
+	for (i = 0; i < creads; i++) {
+		yvals[i] = titsc_readl(ts_dev, REG_FIFO0);
+		yvals[i] &= 0xfff;
+	}
  
-		channel = (read & 0xf0000) >> 16;
-		read &= 0xfff;
-		if (channel > first_step + creads + 2) {
-			diff = abs(read - prev_val_x);
-			if (diff < prev_diff_x) {
-				prev_diff_x = diff;
-				*x = read;
-			}
-			prev_val_x = read;
+	*z1 = titsc_readl(ts_dev, REG_FIFO0);
+	*z1 &= 0xfff;
+	*z2 = titsc_readl(ts_dev, REG_FIFO0);
+	*z2 &= 0xfff;
  
-		} else if (channel == first_step + creads + 1) {
-			*z1 = read;
+	for (i = 0; i < creads; i++) {
+		xvals[i] = titsc_readl(ts_dev, REG_FIFO0);
+		xvals[i] &= 0xfff;
+	}
  
-		} else if (channel == first_step + creads + 2) {
-			*z2 = read;
-
-		} else if (channel > first_step) {
-			diff = abs(read - prev_val_y);
-			if (diff < prev_diff_y) {
-				prev_diff_y = diff;
-				*y = read;
-			}
-			prev_val_y = read;
+	/*
+	 * If co-ordinates readouts is less than 4 then
+	 * report the average. In case of 4 or more
+	 * readouts, sort the co-ordinate samples, drop
+	 * min and max values and report the average of
+	 * remaining values.
+	 */
+	if (creads <=  3) {
+		for (i = 0; i < creads; i++) {
+			ysum += yvals[i];
+			xsum += xvals[i];
 		}
+		ysum /= creads;
+		xsum /= creads;
+	} else {
+		sort(yvals, creads, sizeof(unsigned int),
+		     titsc_cmp_coord, NULL);
+		sort(xvals, creads, sizeof(unsigned int),
+		     titsc_cmp_coord, NULL);
+		for (i = 1; i < creads - 1; i++) {
+			ysum += yvals[i];
+			xsum += xvals[i];
+		}
+		ysum /= creads - 2;
+		xsum /= creads - 2;
 	}
+	*y = ysum;
+	*x = xsum;
 }
  
 static irqreturn_t titsc_irq(int irq, void *dev)
@@ -363,6 +369,12 @@
 				&ts_dev->coordinate_readouts);
 	if (err < 0)
 		return err;
+
+	if (ts_dev->coordinate_readouts <= 0) {
+		dev_warn(&pdev->dev,
+			 "invalid co-ordinate readouts, resetting it to 5\n");
+		ts_dev->coordinate_readouts = 5;
+	}
  
 	err = of_property_read_u32(node, "ti,charge-delay",
 				   &ts_dev->charge_delay);
...	...	@@ -26,6 +26,7 @@
26	26	#include <linux/delay.h>
27	27	#include <linux/of.h>
28	28	#include <linux/of_device.h>
	29	+#include <linux/sort.h>
29	30
30	31	#include <linux/mfd/ti_am335x_tscadc.h>
31	32
32	33
33	34
34	35
35	36
36	37
37	38
38	39
39	40
...	...	@@ -204,56 +205,61 @@
204	205	am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
205	206	}
206	207
	208	+static int titsc_cmp_coord(const void a, const void b)
	209	+{
	210	+ return (int )a - (int )b;
	211	+}
	212	+
207	213	static void titsc_read_coordinates(struct titsc *ts_dev,
208	214	u32 x, u32 y, u32 z1, u32 z2)
209	215	{
210		- unsigned int fifocount = titsc_readl(ts_dev, REG_FIFO0CNT);
211		- unsigned int prev_val_x = ~0, prev_val_y = ~0;
212		- unsigned int prev_diff_x = ~0, prev_diff_y = ~0;
213		- unsigned int read, diff;
214		- unsigned int i, channel;
	216	+ unsigned int yvals[7], xvals[7];
	217	+ unsigned int i, xsum = 0, ysum = 0;
215	218	unsigned int creads = ts_dev->coordinate_readouts;
216		- unsigned int first_step = TOTAL_STEPS - (creads * 2 + 2);
217	219
218		- z1 = z2 = 0;
219		- if (fifocount % (creads * 2 + 2))
220		- fifocount -= fifocount % (creads * 2 + 2);
221		- /*
222		- * Delta filter is used to remove large variations in sampled
223		- * values from ADC. The filter tries to predict where the next
224		- * coordinate could be. This is done by taking a previous
225		- * coordinate and subtracting it form current one. Further the
226		- * algorithm compares the difference with that of a present value,
227		- * if true the value is reported to the sub system.
228		- */
229		- for (i = 0; i < fifocount; i++) {
230		- read = titsc_readl(ts_dev, REG_FIFO0);
	220	+ for (i = 0; i < creads; i++) {
	221	+ yvals[i] = titsc_readl(ts_dev, REG_FIFO0);
	222	+ yvals[i] &= 0xfff;
	223	+ }
231	224
232		- channel = (read & 0xf0000) >> 16;
233		- read &= 0xfff;
234		- if (channel > first_step + creads + 2) {
235		- diff = abs(read - prev_val_x);
236		- if (diff < prev_diff_x) {
237		- prev_diff_x = diff;
238		- *x = read;
239		- }
240		- prev_val_x = read;
	225	+ *z1 = titsc_readl(ts_dev, REG_FIFO0);
	226	+ *z1 &= 0xfff;
	227	+ *z2 = titsc_readl(ts_dev, REG_FIFO0);
	228	+ *z2 &= 0xfff;
241	229
242		- } else if (channel == first_step + creads + 1) {
243		- *z1 = read;
	230	+ for (i = 0; i < creads; i++) {
	231	+ xvals[i] = titsc_readl(ts_dev, REG_FIFO0);
	232	+ xvals[i] &= 0xfff;
	233	+ }
244	234
245		- } else if (channel == first_step + creads + 2) {
246		- *z2 = read;
247		-
248		- } else if (channel > first_step) {
249		- diff = abs(read - prev_val_y);
250		- if (diff < prev_diff_y) {
251		- prev_diff_y = diff;
252		- *y = read;
253		- }
254		- prev_val_y = read;
	235	+ /*
	236	+ * If co-ordinates readouts is less than 4 then
	237	+ * report the average. In case of 4 or more
	238	+ * readouts, sort the co-ordinate samples, drop
	239	+ * min and max values and report the average of
	240	+ * remaining values.
	241	+ */
	242	+ if (creads <= 3) {
	243	+ for (i = 0; i < creads; i++) {
	244	+ ysum += yvals[i];
	245	+ xsum += xvals[i];
255	246	}
	247	+ ysum /= creads;
	248	+ xsum /= creads;
	249	+ } else {
	250	+ sort(yvals, creads, sizeof(unsigned int),
	251	+ titsc_cmp_coord, NULL);
	252	+ sort(xvals, creads, sizeof(unsigned int),
	253	+ titsc_cmp_coord, NULL);
	254	+ for (i = 1; i < creads - 1; i++) {
	255	+ ysum += yvals[i];
	256	+ xsum += xvals[i];
	257	+ }
	258	+ ysum /= creads - 2;
	259	+ xsum /= creads - 2;
256	260	}
	261	+ *y = ysum;
	262	+ *x = xsum;
257	263	}
258	264
259	265	static irqreturn_t titsc_irq(int irq, void *dev)
...	...	@@ -363,6 +369,12 @@
363	369	&ts_dev->coordinate_readouts);
364	370	if (err < 0)
365	371	return err;
	372	+
	373	+ if (ts_dev->coordinate_readouts <= 0) {
	374	+ dev_warn(&pdev->dev,
	375	+ "invalid co-ordinate readouts, resetting it to 5\n");
	376	+ ts_dev->coordinate_readouts = 5;
	377	+ }
366	378
367	379	err = of_property_read_u32(node, "ti,charge-delay",
368	380	&ts_dev->charge_delay);