From: Wenyou Yang <wenyou.yang@xxxxxxxxx>
Add the HOLD field setting in order to support I2C slave devices which need
a longer hold time of the data.
Since it depends on the slave devices connected to the bus, add a DT
property "atmel,twd-hold-cycles" to specify this HOLD field.
Signed-off-by: Wenyou Yang <wenyou.yang@xxxxxxxxx>
Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
---
drivers/i2c/busses/i2c-at91.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 1c758cd..06e66ef 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -64,6 +64,7 @@
#define AT91_TWI_IADR 0x000c /* Internal Address Register */
#define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
+#define AT91_TWI_CWGR_HOLD(x) (((x) & 0x1f) << 24)
#define AT91_TWI_SR 0x0020 /* Status Register */
#define AT91_TWI_TXCOMP BIT(0) /* Transmission Complete */
@@ -185,7 +186,8 @@ static void at91_init_twi_bus(struct at91_twi_dev *dev)
* Calculate symmetric clock as stated in datasheet:
* twi_clk = F_MAIN / (2 * (cdiv * (1 << ckdiv) + offset))
*/
-static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
+static void at91_calc_twi_clock(struct at91_twi_dev *dev,
+ int twi_clk, u32 twd_hold)
{
int ckdiv, cdiv, div;
struct at91_twi_pdata *pdata = dev->pdata;
@@ -204,7 +206,9 @@ static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
cdiv = 255;
}
- dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv;
+ dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
+ | AT91_TWI_CWGR_HOLD(twd_hold);
+
dev_dbg(dev->dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
}
@@ -936,6 +940,7 @@ static int at91_twi_probe(struct platform_device *pdev)
int rc;
u32 phy_addr;
u32 bus_clk_rate;
+ u32 twd_hold_cycles;
dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
if (!dev)
@@ -992,7 +997,12 @@ static int at91_twi_probe(struct platform_device *pdev)
if (rc)
bus_clk_rate = DEFAULT_TWI_CLK_HZ;
- at91_calc_twi_clock(dev, bus_clk_rate);
+ rc = of_property_read_u32(dev->dev->of_node,
+ "atmel,twd-hold-cycles", &twd_hold_cycles);
+ if (rc)
+ twd_hold_cycles = 0;
+
+ at91_calc_twi_clock(dev, bus_clk_rate, twd_hold_cycles);
at91_init_twi_bus(dev);
snprintf(dev->adapter.name, sizeof(dev->adapter.name), "AT91");
--
2.5.0
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