#include <linux/wait.h>
#include <linux/mfd/syscon.h>
#include <linux/regmap.h>
+#include <linux/math64.h>
/* Register Map */
/* Hardware resources */
void __iomem *regs;
struct clk *clk;
+ struct notifier_block clk_rate_nb;
/* Settings */
unsigned int scl_frequency;
return IRQ_HANDLED;
}
-static void rk3x_i2c_set_scl_rate(struct rk3x_i2c *i2c, unsigned long scl_rate)
+/**
+ * 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 i2c_rate = clk_get_rate(i2c->clk);
- unsigned int div;
+ 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 clk_rate_khz, scl_rate_khz;
+
+ unsigned long min_low_div, min_high_div;
+ unsigned long max_low_div;
+
+ 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;
+
+ /* prevent scl_rate_khz from becoming 0 */
+ if (WARN_ON(scl_rate < 1000))
+ scl_rate = 1000;
+
+ /*
+ * min_low_ns: The minimum number of ns we need to hold low
+ * to meet i2c spec
+ * min_high_ns: The minimum number of ns we need to hold high
+ * to meet i2c spec
+ * max_low_ns: The maximum number of ns we can hold low
+ * to meet i2c spec
+ *
+ * Note: max_low_ns should be (max data hold time * 2 - buffer)
+ * This is because the i2c host on Rockchip holds the data line
+ * for half the low time.
+ */
+ if (scl_rate <= 100000) {
+ min_low_ns = 4700;
+ min_high_ns = 4000;
+ max_data_hold_ns = 3450;
+ data_hold_buffer_ns = 50;
+ } else {
+ min_low_ns = 1300;
+ min_high_ns = 600;
+ max_data_hold_ns = 900;
+ data_hold_buffer_ns = 50;
+ }
+ max_low_ns = max_data_hold_ns * 2 - data_hold_buffer_ns;
+ min_total_ns = min_low_ns + min_high_ns;
+
+ /* Adjust to avoid overflow */
+ 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(clk_rate_khz, scl_rate_khz * 8);
+
+ /* These are the min dividers needed for min hold times. */
+ 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 = clk_rate_khz * max_low_ns / (8 * 1000000);
+
+ if (min_low_div > max_low_div) {
+ WARN_ONCE(true,
+ "Conflicting, min_low_div %lu, max_low_div %lu\n",
+ min_low_div, max_low_div);
+ max_low_div = min_low_div;
+ }
+
+ if (min_div_for_hold > min_total_div) {
+ /*
+ * Time needed to meet hold requirements is important.
+ * Just use that.
+ */
+ *div_low = min_low_div;
+ *div_high = min_high_div;
+ } else {
+ /*
+ * We've got to distribute some time among the low and high
+ * so we don't run too fast.
+ */
+ extra_div = min_total_div - min_div_for_hold;
+
+ /*
+ * We'll try to split things up perfectly evenly,
+ * biasing slightly towards having a higher div
+ * for low (spend more time low).
+ */
+ 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 */
+ if (ideal_low_div > max_low_div)
+ ideal_low_div = max_low_div;
+
+ /*
+ * Handle when the ideal low div is going to take up
+ * more than we have.
+ */
+ if (ideal_low_div > min_low_div + extra_div)
+ ideal_low_div = min_low_div + extra_div;
- /* set DIV = DIVH = DIVL
- * SCL rate = (clk rate) / (8 * (DIVH + 1 + DIVL + 1))
- * = (clk rate) / (16 * (DIV + 1))
+ /* Give low the "ideal" and give high whatever extra is left */
+ extra_low_div = ideal_low_div - min_low_div;
+ *div_low = ideal_low_div;
+ *div_high = min_high_div + (extra_div - extra_low_div);
+ }
+
+ /*
+ * Adjust to the fact that the hardware has an implicit "+1".
+ * NOTE: Above calculations always produce div_low > 0 and div_high > 0.
*/
- div = DIV_ROUND_UP(i2c_rate, scl_rate * 16) - 1;
+ *div_low = *div_low - 1;
+ *div_high = *div_high - 1;
+
+ /* 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 void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
+{
+ unsigned long div_low, div_high;
+ u64 t_low_ns, t_high_ns;
+ int 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);
- i2c_writel(i2c, (div << 16) | (div & 0xffff), REG_CLKDIV);
+ 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 %uns, Act low %lluns high %lluns\n",
+ clk_rate / 1000,
+ 1000000000 / i2c->scl_frequency,
+ t_low_ns, t_high_ns);
+}
+
+/**
+ * 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;
+ }
}
/**
clk_enable(i2c->clk);
- /* The clock rate might have changed, so setup the divider again */
- rk3x_i2c_set_scl_rate(i2c, i2c->scl_frequency);
-
i2c->is_last_msg = false;
/*
int bus_nr;
u32 value;
int irq;
+ unsigned long clk_rate;
i2c = devm_kzalloc(&pdev->dev, sizeof(struct rk3x_i2c), GFP_KERNEL);
if (!i2c)
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;
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;
projects / linux-drm-fsl-dcu.git / blobdiff