i2c: at91: add support for analog filtering

Add support for analog filtering for i2c lines.
The sama5d2 and sam9x60 support this feature.
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-at91-core.c

@@ -70,6 +70,7 @@ static struct at91_twi_pdata at91rm9200_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9261_config = {
@@ -80,6 +81,7 @@ static struct at91_twi_pdata at91sam9261_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9260_config = {
@@ -90,6 +92,7 @@ static struct at91_twi_pdata at91sam9260_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9g20_config = {
@@ -100,6 +103,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9g10_config = {
@@ -110,6 +114,7 @@ static struct at91_twi_pdata at91sam9g10_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static const struct platform_device_id at91_twi_devtypes[] = {
@@ -142,6 +147,7 @@ static struct at91_twi_pdata at91sam9x5_config = {
 	.has_hold_field = false,
 	.has_dig_filtr = false,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata sama5d4_config = {
@@ -152,6 +158,7 @@ static struct at91_twi_pdata sama5d4_config = {
 	.has_hold_field = true,
 	.has_dig_filtr = true,
 	.has_adv_dig_filtr = false,
+	.has_ana_filtr = false,
 };
 
 static struct at91_twi_pdata sama5d2_config = {
@@ -162,6 +169,7 @@ static struct at91_twi_pdata sama5d2_config = {
 	.has_hold_field = true,
 	.has_dig_filtr = true,
 	.has_adv_dig_filtr = true,
+	.has_ana_filtr = true,
 };
 
 static struct at91_twi_pdata sam9x60_config = {
@@ -172,6 +180,7 @@ static struct at91_twi_pdata sam9x60_config = {
 	.has_hold_field = true,
 	.has_dig_filtr = true,
 	.has_adv_dig_filtr = true,
+	.has_ana_filtr = true,
 };
 
 static const struct of_device_id atmel_twi_dt_ids[] = {

drivers/i2c/busses/i2c-at91-master.c

@@ -32,6 +32,7 @@
 void at91_init_twi_bus_master(struct at91_twi_dev *dev)
 {
 	struct at91_twi_pdata *pdata = dev->pdata;
+	u32 filtr = 0;
 
 	/* FIFO should be enabled immediately after the software reset */
 	if (dev->fifo_size)
@@ -42,13 +43,20 @@ void at91_init_twi_bus_master(struct at91_twi_dev *dev)
 
 	/* enable digital filter */
 	if (pdata->has_dig_filtr && dev->enable_dig_filt)
-		at91_twi_write(dev, AT91_TWI_FILTR, AT91_TWI_FILTR_FILT);
+		filtr |= AT91_TWI_FILTR_FILT;
 
 	/* enable advanced digital filter */
 	if (pdata->has_adv_dig_filtr && dev->enable_dig_filt)
-		at91_twi_write(dev, AT91_TWI_FILTR, AT91_TWI_FILTR_FILT |
+		filtr |= AT91_TWI_FILTR_FILT |
 			 (AT91_TWI_FILTR_THRES(dev->filter_width) &
-				AT91_TWI_FILTR_THRES_MASK));
+			 AT91_TWI_FILTR_THRES_MASK);
+
+	/* enable analog filter */
+	if (pdata->has_ana_filtr && dev->enable_ana_filt)
+		filtr |= AT91_TWI_FILTR_PADFEN;
+
+	if (filtr)
+		at91_twi_write(dev, AT91_TWI_FILTR, filtr);
 }
 
 /*
@@ -826,6 +834,8 @@ int at91_twi_probe_master(struct platform_device *pdev,
 	dev->enable_dig_filt = of_property_read_bool(pdev->dev.of_node,
 						     "i2c-digital-filter");
 
+	dev->enable_ana_filt = of_property_read_bool(pdev->dev.of_node,
+						     "i2c-analog-filter");
 	at91_calc_twi_clock(dev);
 
 	dev->adapter.algo = &at91_twi_algorithm;

drivers/i2c/busses/i2c-at91.h

@@ -86,6 +86,7 @@
 
 #define AT91_TWI_FILTR		0x0044
 #define AT91_TWI_FILTR_FILT	BIT(0)
+#define AT91_TWI_FILTR_PADFEN	BIT(1)
 #define AT91_TWI_FILTR_THRES(v)		((v) << 8)
 #define AT91_TWI_FILTR_THRES_MAX	7
 #define AT91_TWI_FILTR_THRES_MASK	GENMASK(10, 8)
@@ -116,6 +117,7 @@ struct at91_twi_pdata {
 	bool has_hold_field;
 	bool has_dig_filtr;
 	bool has_adv_dig_filtr;
+	bool has_ana_filtr;
 	struct at_dma_slave dma_slave;
 };
 
@@ -154,6 +156,7 @@ struct at91_twi_dev {
 	struct i2c_client *slave;
 #endif
 	bool enable_dig_filt;
+	bool enable_ana_filt;
 	u32 filter_width;
 };