@@ -98,6 +98,7 @@ struct rk3x_i2c {
/* Hardware resources */
void __iomem *regs;
struct clk *clk;
+ struct notifier_block clk_rate_nb;
/* Settings */
unsigned int scl_frequency;
@@ -429,15 +430,27 @@ out:
return IRQ_HANDLED;
}
-static int rk3x_i2c_calc_divs(unsigned long i2c_rate, unsigned long scl_rate,
- unsigned long *div_low, unsigned long *div_high)
+/**
+ * Calculate divider values for desired SCL frequency
+ *
+ * @clk_rate: I2C input clock rate
+ * @scl_rate: Desired SCL rate
+ * @div_low: Divider output for low
+ * @div_high: Divider output for high
+ *
+ * Returns: 0 on success, -EINVAL if the goal SCL rate is too slow. In that case
+ * a best-effort divider value is returned in divs. If the target rate is
+ * too high, we silently use the highest possible rate.
+ */
+static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
+ unsigned long *div_low, unsigned long *div_high)
{
unsigned long min_low_ns, min_high_ns;
unsigned long max_data_hold_ns;
unsigned long data_hold_buffer_ns;
unsigned long max_low_ns, min_total_ns;
- unsigned long i2c_rate_khz, scl_rate_khz;
+ unsigned long clk_rate_khz, scl_rate_khz;
unsigned long min_low_div, min_high_div;
unsigned long max_low_div;
@@ -445,6 +458,8 @@ static int rk3x_i2c_calc_divs(unsigned long i2c_rate, unsigned long scl_rate,
unsigned long min_div_for_hold, min_total_div;
unsigned long extra_div, extra_low_div, ideal_low_div;
+ int ret = 0;
+
/* Only support standard-mode and fast-mode */
if (WARN_ON(scl_rate > 400000))
scl_rate = 400000;
@@ -480,25 +495,25 @@ static int rk3x_i2c_calc_divs(unsigned long i2c_rate, unsigned long scl_rate,
min_total_ns = min_low_ns + min_high_ns;
/* Adjust to avoid overflow */
- i2c_rate_khz = DIV_ROUND_UP(i2c_rate, 1000);
+ clk_rate_khz = DIV_ROUND_UP(clk_rate, 1000);
scl_rate_khz = scl_rate / 1000;
/*
* We need the total div to be >= this number
* so we don't clock too fast.
*/
- min_total_div = DIV_ROUND_UP(i2c_rate_khz, scl_rate_khz * 8);
+ min_total_div = DIV_ROUND_UP(clk_rate_khz, scl_rate_khz * 8);
/* These are the min dividers needed for min hold times. */
- min_low_div = DIV_ROUND_UP(i2c_rate_khz * min_low_ns, 8 * 1000000);
- min_high_div = DIV_ROUND_UP(i2c_rate_khz * min_high_ns, 8 * 1000000);
+ min_low_div = DIV_ROUND_UP(clk_rate_khz * min_low_ns, 8 * 1000000);
+ min_high_div = DIV_ROUND_UP(clk_rate_khz * min_high_ns, 8 * 1000000);
min_div_for_hold = (min_low_div + min_high_div);
/*
* This is the maximum divider so we don't go over the max.
* We don't round up here (we round down) since this is a max.
*/
- max_low_div = i2c_rate_khz * max_low_ns / (8 * 1000000);
+ max_low_div = clk_rate_khz * max_low_ns / (8 * 1000000);
if (min_low_div > max_low_div) {
WARN_ONCE(true,
@@ -526,7 +541,7 @@ static int rk3x_i2c_calc_divs(unsigned long i2c_rate, unsigned long scl_rate,
* biasing slightly towards having a higher div
* for low (spend more time low).
*/
- ideal_low_div = DIV_ROUND_UP(i2c_rate_khz * min_low_ns,
+ ideal_low_div = DIV_ROUND_UP(clk_rate_khz * min_low_ns,
scl_rate_khz * 8 * min_total_ns);
/* Don't allow it to go over the max */
@@ -547,40 +562,99 @@ static int rk3x_i2c_calc_divs(unsigned long i2c_rate, unsigned long scl_rate,
}
/*
- * Adjust to the fact that the hardware has an implicit "+1".
- * NOTE: Above calculations always produce div_low > 0 and div_high > 0.
- */
+ * Adjust to the fact that the hardware has an implicit "+1".
+ * NOTE: Above calculations always produce div_low > 0 and div_high > 0.
+ */
*div_low = *div_low - 1;
*div_high = *div_high - 1;
- if (*div_low >= 0xffff || *div_high >= 0xffff)
- return -EINVAL;
- else
- return 0;
+ /* Maximum divider supported by hw is 0xffff */
+ if (*div_low > 0xffff) {
+ *div_low = 0xffff;
+ ret = -EINVAL;
+ }
+
+ if (*div_high > 0xffff) {
+ *div_high = 0xffff;
+ ret = -EINVAL;
+ }
+
+ return ret;
}
-static int rk3x_i2c_set_scl_rate(struct rk3x_i2c *i2c, unsigned long scl_rate)
+static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
{
- unsigned long i2c_rate = clk_get_rate(i2c->clk);
unsigned long div_low, div_high;
u64 t_low_ns, t_high_ns;
- int ret = 0;
+ int ret;
- ret = rk3x_i2c_calc_divs(i2c_rate, scl_rate, &div_low, &div_high);
- if (ret < 0)
- return ret;
+ ret = rk3x_i2c_calc_divs(clk_rate, i2c->scl_frequency, &div_low,
+ &div_high);
+ WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->scl_frequency);
+
+ clk_enable(i2c->clk);
i2c_writel(i2c, (div_high << 16) | (div_low & 0xffff), REG_CLKDIV);
+ clk_disable(i2c->clk);
- t_low_ns = div_u64(((u64)div_low + 1) * 8 * 1000000000, i2c_rate);
- t_high_ns = div_u64(((u64)div_high + 1) * 8 * 1000000000, i2c_rate);
+ t_low_ns = div_u64(((u64)div_low + 1) * 8 * 1000000000, clk_rate);
+ t_high_ns = div_u64(((u64)div_high + 1) * 8 * 1000000000, clk_rate);
dev_dbg(i2c->dev,
- "CLK %lukhz, Req %luns, Act low %lluns high %lluns\n",
- i2c_rate / 1000,
- 1000000000 / scl_rate,
+ "CLK %lukhz, Req %uns, Act low %lluns high %lluns\n",
+ clk_rate / 1000,
+ 1000000000 / i2c->scl_frequency,
t_low_ns, t_high_ns);
+}
- return ret;
+/**
+ * rk3x_i2c_clk_notifier_cb - Clock rate change callback
+ * @nb: Pointer to notifier block
+ * @event: Notification reason
+ * @data: Pointer to notification data object
+ *
+ * The callback checks whether a valid bus frequency can be generated after the
+ * change. If so, the change is acknowledged, otherwise the change is aborted.
+ * New dividers are written to the HW in the pre- or post change notification
+ * depending on the scaling direction.
+ *
+ * Code adapted from i2c-cadence.c.
+ *
+ * Return: NOTIFY_STOP if the rate change should be aborted, NOTIFY_OK
+ * to acknowedge the change, NOTIFY_DONE if the notification is
+ * considered irrelevant.
+ */
+static int rk3x_i2c_clk_notifier_cb(struct notifier_block *nb, unsigned long
+ event, void *data)
+{
+ struct clk_notifier_data *ndata = data;
+ struct rk3x_i2c *i2c = container_of(nb, struct rk3x_i2c, clk_rate_nb);
+ unsigned long div_low, div_high;
+
+ switch (event) {
+ case PRE_RATE_CHANGE:
+ if (rk3x_i2c_calc_divs(ndata->new_rate, i2c->scl_frequency,
+ &div_low, &div_high) != 0) {
+ return NOTIFY_STOP;
+ }
+
+ /* scale up */
+ if (ndata->new_rate > ndata->old_rate)
+ rk3x_i2c_adapt_div(i2c, ndata->new_rate);
+
+ return NOTIFY_OK;
+ case POST_RATE_CHANGE:
+ /* scale down */
+ if (ndata->new_rate < ndata->old_rate)
+ rk3x_i2c_adapt_div(i2c, ndata->new_rate);
+ return NOTIFY_OK;
+ case ABORT_RATE_CHANGE:
+ /* scale up */
+ if (ndata->new_rate > ndata->old_rate)
+ rk3x_i2c_adapt_div(i2c, ndata->old_rate);
+ return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
}
/**
@@ -677,11 +751,6 @@ static int rk3x_i2c_xfer(struct i2c_adapter *adap,
clk_enable(i2c->clk);
- /* The clock rate might have changed, so setup the divider again */
- ret = rk3x_i2c_set_scl_rate(i2c, i2c->scl_frequency);
- if (ret < 0)
- goto exit;
-
i2c->is_last_msg = false;
/*
@@ -728,7 +797,6 @@ static int rk3x_i2c_xfer(struct i2c_adapter *adap,
}
}
-exit:
clk_disable(i2c->clk);
spin_unlock_irqrestore(&i2c->lock, flags);
@@ -768,6 +836,7 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
int bus_nr;
u32 value;
int irq;
+ unsigned long clk_rate;
i2c = devm_kzalloc(&pdev->dev, sizeof(struct rk3x_i2c), GFP_KERNEL);
if (!i2c)
@@ -868,16 +937,28 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
return ret;
}
+ i2c->clk_rate_nb.notifier_call = rk3x_i2c_clk_notifier_cb;
+ ret = clk_notifier_register(i2c->clk, &i2c->clk_rate_nb);
+ if (ret != 0) {
+ dev_err(&pdev->dev, "Unable to register clock notifier\n");
+ goto err_clk;
+ }
+
+ clk_rate = clk_get_rate(i2c->clk);
+ rk3x_i2c_adapt_div(i2c, clk_rate);
+
ret = i2c_add_adapter(&i2c->adap);
if (ret < 0) {
dev_err(&pdev->dev, "Could not register adapter\n");
- goto err_clk;
+ goto err_clk_notifier;
}
dev_info(&pdev->dev, "Initialized RK3xxx I2C bus at %p\n", i2c->regs);
return 0;
+err_clk_notifier:
+ clk_notifier_unregister(i2c->clk, &i2c->clk_rate_nb);
err_clk:
clk_unprepare(i2c->clk);
return ret;
@@ -888,6 +969,8 @@ static int rk3x_i2c_remove(struct platform_device *pdev)
struct rk3x_i2c *i2c = platform_get_drvdata(pdev);
i2c_del_adapter(&i2c->adap);
+
+ clk_notifier_unregister(i2c->clk, &i2c->clk_rate_nb);
clk_unprepare(i2c->clk);
return 0;