diff options
Diffstat (limited to 'drivers/clk/clk-versaclock5.c')
| -rw-r--r-- | drivers/clk/clk-versaclock5.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/drivers/clk/clk-versaclock5.c b/drivers/clk/clk-versaclock5.c index 43db67337bc0..344cd6c61188 100644 --- a/drivers/clk/clk-versaclock5.c +++ b/drivers/clk/clk-versaclock5.c @@ -759,6 +759,63 @@ static int vc5_update_power(struct device_node *np_output, return 0; } +static int vc5_map_cap_value(u32 femtofarads) +{ + int mapped_value; + + /* + * The datasheet explicitly states 9000 - 25000 with 0.5pF + * steps, but the Programmer's guide shows the steps are 0.430pF. + * After getting feedback from Renesas, the .5pF steps were the + * goal, but 430nF was the actual values. + * Because of this, the actual range goes to 22760 instead of 25000 + */ + if (femtofarads < 9000 || femtofarads > 22760) + return -EINVAL; + + /* + * The Programmer's guide shows XTAL[5:0] but in reality, + * XTAL[0] and XTAL[1] are both LSB which makes the math + * strange. With clarfication from Renesas, setting the + * values should be simpler by ignoring XTAL[0] + */ + mapped_value = DIV_ROUND_CLOSEST(femtofarads - 9000, 430); + + /* + * Since the calculation ignores XTAL[0], there is one + * special case where mapped_value = 32. In reality, this means + * the real mapped value should be 111111b. In other cases, + * the mapped_value needs to be shifted 1 to the left. + */ + if (mapped_value > 31) + mapped_value = 0x3f; + else + mapped_value <<= 1; + + return mapped_value; +} +static int vc5_update_cap_load(struct device_node *node, struct vc5_driver_data *vc5) +{ + u32 value; + int mapped_value; + + if (!of_property_read_u32(node, "idt,xtal-load-femtofarads", &value)) { + mapped_value = vc5_map_cap_value(value); + if (mapped_value < 0) + return mapped_value; + + /* + * The mapped_value is really the high 6 bits of + * VC5_XTAL_X1_LOAD_CAP and VC5_XTAL_X2_LOAD_CAP, so + * shift the value 2 places. + */ + regmap_update_bits(vc5->regmap, VC5_XTAL_X1_LOAD_CAP, ~0x03, mapped_value << 2); + regmap_update_bits(vc5->regmap, VC5_XTAL_X2_LOAD_CAP, ~0x03, mapped_value << 2); + } + + return 0; +} + static int vc5_update_slew(struct device_node *np_output, struct vc5_out_data *clk_out) { @@ -884,6 +941,13 @@ static int vc5_probe(struct i2c_client *client, const struct i2c_device_id *id) return -EINVAL; } + /* Configure Optional Loading Capacitance for external XTAL */ + if (!(vc5->chip_info->flags & VC5_HAS_INTERNAL_XTAL)) { + ret = vc5_update_cap_load(client->dev.of_node, vc5); + if (ret) + goto err_clk_register; + } + init.name = kasprintf(GFP_KERNEL, "%pOFn.mux", client->dev.of_node); init.ops = &vc5_mux_ops; init.flags = 0; |