[PATCH 2/4] i2c: i2c-bcm-kona: Add support for high-speed mode

From: Tim Kryger
Date: Mon Oct 07 2013 - 15:16:48 EST

Add support for I2C high-speed mode (3.4 MHz).

Signed-off-by: Tim Kryger <tim.kryger@xxxxxxxxxx>
Reviewed-by: Matt Porter <matt.porter@xxxxxxxxxx>
Reviewed-by: Markus Mayer <markus.mayer@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-bcm-kona.c | 116 ++++++++++++++++++++++++++++++++++++++
1 file changed, 116 insertions(+)

diff --git a/drivers/i2c/busses/i2c-bcm-kona.c b/drivers/i2c/busses/i2c-bcm-kona.c
index 2936acf..458714f 100644
--- a/drivers/i2c/busses/i2c-bcm-kona.c
+++ b/drivers/i2c/busses/i2c-bcm-kona.c
@@ -77,6 +77,9 @@

#define HSTIM_OFFSET 0x00000058
#define HSTIM_HS_MODE_MASK 0x00008000
+#define HSTIM_HS_HOLD_SHIFT 10
+#define HSTIM_HS_HIGH_PHASE_SHIFT 5
+#define HSTIM_HS_SETUP_SHIFT 0

#define PADCTL_OFFSET 0x0000005c
#define PADCTL_PAD_OUT_EN_MASK 0x00000004
@@ -91,6 +94,9 @@
#define MAX_TX_FIFO_SIZE 64U /* bytes */

#define STD_EXT_CLK_FREQ 13000000UL
+#define HS_EXT_CLK_FREQ 104000000UL
+
+#define MASTERCODE 0x08 /* Mastercodes are 0000_1xxxb */

#define I2C_TIMEOUT 100 /* msecs */

@@ -108,6 +114,10 @@ enum bus_speed_index {
BCM_SPD_1MHZ,
};

+enum hs_bus_speed_index {
+ BCM_SPD_3P4MHZ = 0,
+};
+
/* Internal divider settings for standard mode, fast mode and fast mode plus */
struct bus_speed_cfg {
uint8_t time_m; /* Number of cycles for setup time */
@@ -118,12 +128,30 @@ struct bus_speed_cfg {
uint8_t time_div; /* Post-prescale divider */
};

+/* Internal divider settings for high-speed mode */
+struct hs_bus_speed_cfg {
+ uint8_t hs_hold; /* Number of clock cycles SCL stays low until
+ the end of bit period */
+ uint8_t hs_high_phase; /* Number of clock cycles SCL stays high
+ before it falls */
+ uint8_t hs_setup; /* Number of clock cycles SCL stays low
+ before it rises */
+ uint8_t prescale; /* Prescale divider */
+ uint8_t time_p; /* Timing coefficient */
+ uint8_t no_div; /* Disable clock divider */
+ uint8_t time_div; /* Post-prescale divider */
+};
+
static const struct bus_speed_cfg std_cfg_table[] = {
[BCM_SPD_100K] = {0x01, 0x01, 0x03, 0x06, 0x00, 0x02},
[BCM_SPD_400K] = {0x05, 0x01, 0x03, 0x05, 0x01, 0x02},
[BCM_SPD_1MHZ] = {0x01, 0x01, 0x03, 0x01, 0x01, 0x03},
};

+static const struct hs_bus_speed_cfg hs_cfg_table[] = {
+ [BCM_SPD_3P4MHZ] = {0x01, 0x08, 0x14, 0x00, 0x06, 0x01, 0x00},
+};
+
struct bcm_kona_i2c_dev {
/* Pointer to linux device struct */
struct device *device;
@@ -137,6 +165,9 @@ struct bcm_kona_i2c_dev {
/* Standard Speed configuration */
const struct bus_speed_cfg *std_cfg;

+ /* High Speed configuration (if applicable) */
+ const struct hs_bus_speed_cfg *hs_cfg;
+
/* Linux I2C adapter struct */
struct i2c_adapter adapter;

@@ -520,6 +551,72 @@ static void bcm_kona_i2c_config_timing(struct bcm_kona_i2c_dev *dev)
dev->base + CLKEN_OFFSET);
}

+static void bcm_kona_i2c_config_timing_hs(struct bcm_kona_i2c_dev *dev)
+{
+ writel((dev->hs_cfg->prescale << TIM_PRESCALE_SHIFT) |
+ (dev->hs_cfg->time_p << TIM_P_SHIFT) |
+ (dev->hs_cfg->no_div << TIM_NO_DIV_SHIFT) |
+ (dev->hs_cfg->time_div << TIM_DIV_SHIFT),
+ dev->base + TIM_OFFSET);
+
+ writel((dev->hs_cfg->hs_hold << HSTIM_HS_HOLD_SHIFT) |
+ (dev->hs_cfg->hs_high_phase << HSTIM_HS_HIGH_PHASE_SHIFT) |
+ (dev->hs_cfg->hs_setup << HSTIM_HS_SETUP_SHIFT),
+ dev->base + HSTIM_OFFSET);
+
+ writel(readl(dev->base + HSTIM_OFFSET) | HSTIM_HS_MODE_MASK,
+ dev->base + HSTIM_OFFSET);
+}
+
+static int bcm_kona_i2c_switch_to_hs(struct bcm_kona_i2c_dev *dev)
+{
+ int rc;
+
+ /* Send mastercode at standard speed */
+ rc = bcm_kona_i2c_write_byte(dev, MASTERCODE, 1);
+ if (rc < 0) {
+ pr_err("High speed handshake failed\n");
+ return rc;
+ }
+
+ /* Configure external clock to higher frequency */
+ rc = clk_set_rate(dev->external_clk, HS_EXT_CLK_FREQ);
+ if (rc) {
+ dev_err(dev->device, "%s: clk_set_rate returned %d\n",
+ __func__, rc);
+ return rc;
+ }
+
+ /* Reconfigure internal dividers */
+ bcm_kona_i2c_config_timing_hs(dev);
+
+ /* Send a restart command */
+ rc = bcm_kona_send_i2c_cmd(dev, BCM_CMD_RESTART);
+ if (rc < 0) {
+ dev_err(dev->device,
+ "High speed restart command failed rc = %d\n", rc);
+ }
+
+ return rc;
+}
+
+static int bcm_kona_i2c_switch_to_std(struct bcm_kona_i2c_dev *dev)
+{
+ int rc;
+
+ /* Reconfigure internal dividers */
+ bcm_kona_i2c_config_timing(dev);
+
+ /* Configure external clock to lower frequency */
+ rc = clk_set_rate(dev->external_clk, STD_EXT_CLK_FREQ);
+ if (rc) {
+ dev_err(dev->device, "%s: clk_set_rate returned %d\n",
+ __func__, rc);
+ }
+
+ return rc;
+}
+
/* Master transfer function */
static int bcm_kona_i2c_xfer(struct i2c_adapter *adapter,
struct i2c_msg msgs[], int num)
@@ -551,6 +648,13 @@ static int bcm_kona_i2c_xfer(struct i2c_adapter *adapter,
goto xfer_disable_pad;
}

+ /* Switch to high speed if applicable */
+ if (dev->hs_cfg) {
+ rc = bcm_kona_i2c_switch_to_hs(dev);
+ if (rc < 0)
+ goto xfer_send_stop;
+ }
+
/* Loop through all messages */
for (i = 0; i < num; i++) {
pmsg = &msgs[i];
@@ -598,6 +702,13 @@ xfer_send_stop:
/* Send a STOP command */
bcm_kona_send_i2c_cmd(dev, BCM_CMD_STOP);

+ /* Return from high speed if applicable */
+ if (dev->hs_cfg) {
+ int hs_rc = bcm_kona_i2c_switch_to_std(dev);
+ if (hs_rc)
+ rc = hs_rc;
+ }
+
xfer_disable_pad:
/* Disable pad output */
writel(PADCTL_PAD_OUT_EN_MASK, dev->base + PADCTL_OFFSET);
@@ -642,6 +753,11 @@ static int bcm_kona_i2c_assign_bus_speed(struct bcm_kona_i2c_dev *dev)
case 1000000:
dev->std_cfg = &std_cfg_table[BCM_SPD_1MHZ];
break;
+ case 3400000:
+ /* Send mastercode at 100k */
+ dev->std_cfg = &std_cfg_table[BCM_SPD_100K];
+ dev->hs_cfg = &hs_cfg_table[BCM_SPD_3P4MHZ];
+ break;
default:
pr_err("%d hz bus speed not supported\n", bus_speed);
return -EINVAL;
--
1.8.0.1


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