[PATCH 1/4] i2c: at91: add upport for the HOLD field

Ludovic Desroches
2015-12-02T10:39:04Z

The hold field allows to configure the data hold time which can be set
with the help of the generic binding 'i2c-sda-hold-time-ns'. This
feature has been introduced with SAMA5D4 SoC family.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
---
drivers/i2c/busses/i2c-at91.c | 54 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 10835d1..09e1690 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 */
@@ -110,6 +111,7 @@ struct at91_twi_pdata {
unsigned clk_offset;
bool has_unre_flag;
bool has_alt_cmd;
+ bool has_hold_field;
struct at_dma_slave dma_slave;
};

@@ -187,10 +189,13 @@ static void at91_init_twi_bus(struct at91_twi_dev *dev)
*/
static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
{
- int ckdiv, cdiv, div;
+ int ckdiv, cdiv, div, hold = 0;
struct at91_twi_pdata *pdata = dev->pdata;
int offset = pdata->clk_offset;
int max_ckdiv = pdata->clk_max_div;
+ u32 twd_hold_time_ns = 0;
+
+#define MAX_HOLD 31

div = max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk),
2 * twi_clk) - offset);
@@ -204,8 +209,33 @@ 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_dbg(dev->dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
+ if (pdata->has_hold_field) {
+ of_property_read_u32(dev->dev->of_node, "i2c-sda-hold-time-ns",
+ &twd_hold_time_ns);
+
+ /*
+ * hold time = HOLD + 3 x T_peripheral_clock
+ * Use clk rate in kHz to prevent overflows when computing
+ * hold.
+ */
+ hold = DIV_ROUND_UP(twd_hold_time_ns
+ * (clk_get_rate(dev->clk) / 1000), 1000000);
+ hold -= 3;
+ if (hold < 0)
+ hold = 0;
+ if (hold > MAX_HOLD) {
+ dev_warn(dev->dev,
+ "HOLD field set to its maximum value (%d instead of %d)\n",
+ MAX_HOLD, hold);
+ hold = MAX_HOLD;
+ }
+ }
+
+ dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
+ | AT91_TWI_CWGR_HOLD(hold);
+
+ dev_dbg(dev->dev, "cdiv %d ckdiv %d hold %d (%d ns)\n",
+ cdiv, ckdiv, hold, twd_hold_time_ns);
}

static void at91_twi_dma_cleanup(struct at91_twi_dev *dev)
@@ -797,6 +827,7 @@ static struct at91_twi_pdata at91rm9200_config = {
.clk_offset = 3,
.has_unre_flag = true,
.has_alt_cmd = false,
+ .has_hold_field = false,
};

static struct at91_twi_pdata at91sam9261_config = {
@@ -804,6 +835,7 @@ static struct at91_twi_pdata at91sam9261_config = {
.clk_offset = 4,
.has_unre_flag = false,
.has_alt_cmd = false,
+ .has_hold_field = false,
};

static struct at91_twi_pdata at91sam9260_config = {
@@ -811,6 +843,7 @@ static struct at91_twi_pdata at91sam9260_config = {
.clk_offset = 4,
.has_unre_flag = false,
.has_alt_cmd = false,
+ .has_hold_field = false,
};

static struct at91_twi_pdata at91sam9g20_config = {
@@ -818,6 +851,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
.clk_offset = 4,
.has_unre_flag = false,
.has_alt_cmd = false,
+ .has_hold_field = false,
};

static struct at91_twi_pdata at91sam9g10_config = {
@@ -825,6 +859,7 @@ static struct at91_twi_pdata at91sam9g10_config = {
.clk_offset = 4,
.has_unre_flag = false,
.has_alt_cmd = false,
+ .has_hold_field = false,
};

static const struct platform_device_id at91_twi_devtypes[] = {
@@ -854,6 +889,15 @@ static struct at91_twi_pdata at91sam9x5_config = {
.clk_offset = 4,
.has_unre_flag = false,
.has_alt_cmd = false,
+ .has_hold_field = false,
+};
+
+static struct at91_twi_pdata sama5d4_config = {
+ .clk_max_div = 7,
+ .clk_offset = 4,
+ .has_unre_flag = false,
+ .has_alt_cmd = false,
+ .has_hold_field = true,
};

static struct at91_twi_pdata sama5d2_config = {
@@ -861,6 +905,7 @@ static struct at91_twi_pdata sama5d2_config = {
.clk_offset = 4,
.has_unre_flag = true,
.has_alt_cmd = true,
+ .has_hold_field = true,
};

static const struct of_device_id atmel_twi_dt_ids[] = {
@@ -883,6 +928,9 @@ static const struct of_device_id atmel_twi_dt_ids[] = {
.compatible = "atmel,at91sam9x5-i2c",
.data = &at91sam9x5_config,
}, {
+ .compatible = "atmel,sama5d4-i2c",
+ .data = &sama5d4_config,
+ }, {
.compatible = "atmel,sama5d2-i2c",
.data = &sama5d2_config,
}, {
--
2.5.0