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>

Author: ehristev

drivers/i2c/busses/i2c-at91.c

@@ -90,6 +90,9 @@
 #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)
@@ -114,6 +117,7 @@ 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;
 };
 
@@ -146,6 +150,7 @@ struct at91_twi_dev {
 	bool recv_len_abort;
 	u32 fifo_size;
 	struct at91_twi_dma dma;
+	bool enable_dig_filt;
 };
 
 static unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg)
@@ -176,6 +181,8 @@ static void at91_twi_irq_restore(struct at91_twi_dev *dev)
 
 static void at91_init_twi_bus(struct at91_twi_dev *dev)
 {
+	struct at91_twi_pdata *pdata = dev->pdata;
+
 	at91_disable_twi_interrupts(dev);
 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SWRST);
 	/* FIFO should be enabled immediately after the software reset */
@@ -184,6 +191,10 @@ static void at91_init_twi_bus(struct at91_twi_dev *dev)
 	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);
 }
 
 /*
@@ -831,6 +842,7 @@ 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 = {
@@ -839,6 +851,7 @@ 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 = {
@@ -847,6 +860,7 @@ 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 = {
@@ -855,6 +869,7 @@ 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 = {
@@ -863,6 +878,7 @@ 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[] = {
@@ -893,6 +909,7 @@ 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 = {
@@ -901,6 +918,7 @@ 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 = {
@@ -909,6 +927,7 @@ 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 = {
@@ -917,6 +936,7 @@ 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[] = {
@@ -1116,6 +1136,9 @@ static int at91_twi_probe(struct platform_device *pdev)
 	if (rc)
 		bus_clk_rate = DEFAULT_TWI_CLK_HZ;
 
+	dev->enable_dig_filt = of_property_read_bool(pdev->dev.of_node,
+						     "enable-dig-filt");
+
 	at91_calc_twi_clock(dev, bus_clk_rate);
 	at91_init_twi_bus(dev);