i2c: at91: add support for digital filtering

Add new platform data support for digital filtering for i2c.
The sama5d4, 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

@@ -68,6 +68,7 @@ static struct at91_twi_pdata at91rm9200_config = {
 	.has_unre_flag = true,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9261_config = {
@@ -76,6 +77,7 @@ static struct at91_twi_pdata at91sam9261_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9260_config = {
@@ -84,6 +86,7 @@ static struct at91_twi_pdata at91sam9260_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9g20_config = {
@@ -92,6 +95,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static struct at91_twi_pdata at91sam9g10_config = {
@@ -100,6 +104,7 @@ static struct at91_twi_pdata at91sam9g10_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static const struct platform_device_id at91_twi_devtypes[] = {
@@ -130,6 +135,7 @@ static struct at91_twi_pdata at91sam9x5_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
+	.has_dig_filtr = false,
 };
 
 static struct at91_twi_pdata sama5d4_config = {
@@ -138,6 +144,7 @@ static struct at91_twi_pdata sama5d4_config = {
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = true,
+	.has_dig_filtr = true,
 };
 
 static struct at91_twi_pdata sama5d2_config = {
@@ -146,6 +153,7 @@ static struct at91_twi_pdata sama5d2_config = {
 	.has_unre_flag = true,
 	.has_alt_cmd = true,
 	.has_hold_field = true,
+	.has_dig_filtr = true,
 };
 
 static struct at91_twi_pdata sam9x60_config = {
@@ -154,6 +162,7 @@ static struct at91_twi_pdata sam9x60_config = {
 	.has_unre_flag = true,
 	.has_alt_cmd = true,
 	.has_hold_field = true,
+	.has_dig_filtr = true,
 };
 
 static const struct of_device_id atmel_twi_dt_ids[] = {

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

@@ -31,12 +31,18 @@
 
 void at91_init_twi_bus_master(struct at91_twi_dev *dev)
 {
+	struct at91_twi_pdata *pdata = dev->pdata;
+
 	/* FIFO should be enabled immediately after the software reset */
 	if (dev->fifo_size)
 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_FIFOEN);
 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSEN);
 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVDIS);
 	at91_twi_write(dev, AT91_TWI_CWGR, dev->twi_cwgr_reg);
+
+	/* enable digital filter */
+	if (pdata->has_dig_filtr && dev->enable_dig_filt)
+		at91_twi_write(dev, AT91_TWI_FILTR, AT91_TWI_FILTR_FILT);
 }
 
 /*
@@ -793,6 +799,9 @@ int at91_twi_probe_master(struct platform_device *pdev,
 		dev_info(dev->dev, "Using FIFO (%u data)\n", dev->fifo_size);
 	}
 
+	dev->enable_dig_filt = of_property_read_bool(pdev->dev.of_node,
+						     "i2c-digital-filter");
+
 	at91_calc_twi_clock(dev);
 
 	dev->adapter.algo = &at91_twi_algorithm;

drivers/i2c/busses/i2c-at91.h

@@ -84,6 +84,9 @@
 #define	AT91_TWI_ACR_DATAL(len)	((len) & 0xff)
 #define	AT91_TWI_ACR_DIR	BIT(8)
 
+#define AT91_TWI_FILTR		0x0044
+#define AT91_TWI_FILTR_FILT	BIT(0)
+
 #define	AT91_TWI_FMR		0x0050	/* FIFO Mode Register */
 #define	AT91_TWI_FMR_TXRDYM(mode)	(((mode) & 0x3) << 0)
 #define	AT91_TWI_FMR_TXRDYM_MASK	(0x3 << 0)
@@ -108,6 +111,7 @@ struct at91_twi_pdata {
 	bool has_unre_flag;
 	bool has_alt_cmd;
 	bool has_hold_field;
+	bool has_dig_filtr;
 	struct at_dma_slave dma_slave;
 };
 
@@ -145,6 +149,7 @@ struct at91_twi_dev {
 	unsigned smr;
 	struct i2c_client *slave;
 #endif
+	bool enable_dig_filt;
 };
 
 unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg);