Hi,
On 07/21/2014 11:38 PM, Tuomas Tynkkynen wrote:
With closed loop support, the clock rate of the DFLL can be adjusted.
The oscillator itself in the DFLL is a free-running oscillator whose
rate is directly determined the supply voltage. However, the DFLL
module contains logic to compare the DFLL output rate to a fixed
reference clock (51 MHz) and make a decision to either lower or raise
the DFLL supply voltage. The DFLL module can then autonomously change
the supply voltage by communicating with an off-chip PMIC via either I2C
or PWM signals. This driver currently supports only I2C.
Signed-off-by: Tuomas Tynkkynen <ttynkkynen@xxxxxxxxxx>
---
v2 changes:
- query the various properties required for I2C mode from the
regulator framework
drivers/clk/tegra/clk-dfll.c | 656 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 653 insertions(+), 3 deletions(-)
diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
index d83e859..0d4b2dd 100644
--- a/drivers/clk/tegra/clk-dfll.c
+++ b/drivers/clk/tegra/clk-dfll.c
@@ -205,12 +205,16 @@
...
+
+/**
+ * dfll_calculate_rate_request - calculate DFLL parameters for a given rate
+ * @td: DFLL instance
+ * @req: DFLL-rate-request structure
+ * @rate: the desired DFLL rate
+ *
+ * Populate the DFLL-rate-request record @req fields with the scale_bits
+ * and mult_bits fields, based on the target input rate. Returns 0 upon
+ * success, or -EINVAL if the requested rate in req->rate is too high
+ * or low for the DFLL to generate.
+ */
+static int dfll_calculate_rate_request(struct tegra_dfll *td,
+ struct dfll_rate_req *req,
+ unsigned long rate)
+{
+ u32 val;
+
+ /*
+ * If requested rate is below the minimum DVCO rate, active the scaler.
+ * In the future the DVCO minimum voltage should be selected based on
+ * chip temperature and the actual minimum rate should be calibrated
+ * at runtime.
+ */
+ req->scale_bits = DFLL_FREQ_REQ_SCALE_MAX - 1;
+ if (rate < td->dvco_rate_min) {
+ int scale;
+
+ scale = DIV_ROUND_CLOSEST(rate / 1000 * DFLL_FREQ_REQ_SCALE_MAX,
+ td->dvco_rate_min / 1000);
+ if (!scale) {
+ dev_err(td->dev, "%s: Rate %lu is too low\n",
+ __func__, rate);
+ return -EINVAL;
+ }
+ req->scale_bits = scale - 1;
+ rate = td->dvco_rate_min;
+ }
+
+ /* Convert requested rate into frequency request and scale settings */
+ val = DVCO_RATE_TO_MULT(rate, td->ref_rate);
+ if (val > FREQ_MAX) {
+ dev_err(td->dev, "%s: Rate %lu is above dfll range\n",
+ __func__, rate);
+ return -EINVAL;
+ }
+ req->mult_bits = val;
+ req->dvco_target_rate = MULT_TO_DVCO_RATE(req->mult_bits, td->ref_rate);
+ req->rate = dfll_scale_dvco_rate(req->dvco_target_rate,
+ req->scale_bits);
Should be dfll_scale_dvco_rate(req->scale_bits, req->dvco_target_rate);
Thanks,
Vince
+ req->lut_index = find_lut_index_for_rate(td, req->dvco_target_rate);
+ if (req->lut_index < 0)
+ return req->lut_index;
+
+ return 0;
+}
+
--
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