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rtc: pcf85063: support loading quartz-load capacitance from device tree

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Use previously ignored quartz-load-femtofarads property from device tree
to set load capacitance. If missing, leave the device unconfigured
as a default might have been set. force_cap is left out for now but
can be retrofitted in the future as there may be different hardware
without the 12.500pF flag.

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Signed-off-by: Alexander Feilke <alexander.feilke@ew.tq-group.com>
This commit is contained in:
Alexander Feilke
2026-05-22 17:39:27 +02:00
committed by Tom Rini
parent 2b6de25797
commit d8f535cd8f
1 changed files with 38 additions and 0 deletions
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38
drivers/rtc/pcf85063.c
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@@ -140,6 +140,30 @@ static int pcf85063_write(struct udevice *dev, unsigned int offset,
return dm_i2c_write(dev, offset, buf, len);
}
static int pcf85063_load_capacitance(struct udevice *dev)
{
u32 load = 7000;
u8 reg = 0;
if (ofnode_read_u32(dev_ofnode(dev), "quartz-load-femtofarads", &load))
return 0;
switch (load) {
default:
dev_warn(dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
load);
fallthrough;
case 7000:
break;
case 12500:
reg = PCF85063_REG_CTRL1_CAP_SEL;
break;
}
return dm_i2c_reg_clrset(dev, PCF85063_REG_CTRL1,
PCF85063_REG_CTRL1_CAP_SEL, reg);
}
static const struct rtc_ops pcf85063_rtc_ops = {
.get = pcf85063_get_time,
.set = pcf85063_set_time,
@@ -150,8 +174,22 @@ static const struct rtc_ops pcf85063_rtc_ops = {
static int pcf85063_probe(struct udevice *dev)
{
u8 tmp;
int err;
i2c_set_chip_flags(dev, DM_I2C_CHIP_RD_ADDRESS | DM_I2C_CHIP_WR_ADDRESS);
err = dm_i2c_read(dev, PCF85063_REG_SC, &tmp, sizeof(tmp));
if (err) {
dev_err(dev, "RTC chip is not present\n");
return err;
}
err = pcf85063_load_capacitance(dev);
if (err < 0)
dev_warn(dev, "failed to set xtal load capacitance: %d",
err);
return 0;
}