[PATCH 2/2] i2c: at91: add support for brsrcclk

[Horatiu Vultur]

This allows to set the TWI bite rate based on a programmable clock source.
The lan966x supports this feature.

Signed-off-by: Horatiu Vultur <horatiu.vultur at microchip.com>
---
 drivers/i2c/busses/i2c-at91-core.c   | 16 ++++++++++++++++
 drivers/i2c/busses/i2c-at91-master.c | 23 +++++++++++++++++++++--
 drivers/i2c/busses/i2c-at91.h        |  1 +
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index 2df9df585131..d98b437e5775 100644
--- a/drivers/i2c/busses/i2c-at91-core.c
+++ b/drivers/i2c/busses/i2c-at91-core.c
@@ -146,6 +146,19 @@ static struct at91_twi_pdata sam9x60_config = {
 	.has_clear_cmd = true,
 };
 
+static struct at91_twi_pdata lan966x_config = {
+	.clk_max_div = 7,
+	.clk_offset = 0,
+	.clk_brsrcclk = true,
+	.has_unre_flag = true,
+	.has_alt_cmd = true,
+	.has_hold_field = true,
+	.has_dig_filtr = true,
+	.has_adv_dig_filtr = true,
+	.has_ana_filtr = true,
+	.has_clear_cmd = true,
+};
+
 static const struct of_device_id atmel_twi_dt_ids[] = {
 	{
 		.compatible = "atmel,at91rm9200-i2c",
@@ -174,6 +187,9 @@ static const struct of_device_id atmel_twi_dt_ids[] = {
 	}, {
 		.compatible = "microchip,sam9x60-i2c",
 		.data = &sam9x60_config,
+	}, {
+		.compatible = "microchip,lan966x-i2c",
+		.data = &lan966x_config,
 	}, {
 		/* sentinel */
 	}
diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
index b0eae94909f4..f504af30adbe 100644
--- a/drivers/i2c/busses/i2c-at91-master.c
+++ b/drivers/i2c/busses/i2c-at91-master.c
@@ -120,8 +120,27 @@ static void at91_calc_twi_clock(struct at91_twi_dev *dev)
 		}
 	}
 
-	dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
-			    | AT91_TWI_CWGR_HOLD(hold);
+	if (pdata->clk_brsrcclk) {
+		u8 chdiv, cldiv, gck_pr;
+
+		gck_pr = 1000000000 / clk_get_rate(dev->clk);
+
+		/* thigh = bus_freq_hz in ns * 0.4
+		 * tlow = bus_freq_hz in ns * 0.6
+		 * chdiv = (thigh / GCK_PR)/2 ^ CKDIV
+		 * cldiv = (tlow / GCK_PR)/2 ^ CKDIV
+		 * where ckdiv = 0;
+		 */
+		cldiv = (1000000000 / t->bus_freq_hz * 6 / 10) / gck_pr;
+		chdiv = (1000000000 / t->bus_freq_hz * 4 / 10) / gck_pr;
+
+		dev->twi_cwgr_reg = (chdiv << 8) | cldiv
+			| AT91_TWI_CWGR_HOLD(hold)
+			| pdata->clk_brsrcclk << 20;
+	} else {
+		dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
+			| AT91_TWI_CWGR_HOLD(hold);
+	}
 
 	dev->filter_width = filter_width;
 
diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
index 942e9c3973bb..f7328fbe8eb8 100644
--- a/drivers/i2c/busses/i2c-at91.h
+++ b/drivers/i2c/busses/i2c-at91.h
@@ -115,6 +115,7 @@
 struct at91_twi_pdata {
 	unsigned clk_max_div;
 	unsigned clk_offset;
+	bool clk_brsrcclk;
 	bool has_unre_flag;
 	bool has_alt_cmd;
 	bool has_hold_field;
-- 
2.33.0