at86rf230: add support for external xtal trim
This patch adds support for setting the xtal trim register. Some at86rf2xx
transceiver boards needs fine tuning the xtal capacitor.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
index 9888b7f..c1323e5 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -1315,7 +1315,7 @@
.get_desense_steps = at86rf212_get_desens_steps
};
-static int at86rf230_hw_init(struct at86rf230_local *lp)
+static int at86rf230_hw_init(struct at86rf230_local *lp, u8 xtal_trim)
{
int rc, irq_type, irq_pol = IRQ_ACTIVE_HIGH;
unsigned int dvdd;
@@ -1362,6 +1362,45 @@
usleep_range(lp->data->t_sleep_cycle,
lp->data->t_sleep_cycle + 100);
+ /* xtal_trim value is calculated by:
+ * CL = 0.5 * (CX + CTRIM + CPAR)
+ *
+ * whereas:
+ * CL = capacitor of used crystal
+ * CX = connected capacitors at xtal pins
+ * CPAR = in all at86rf2xx datasheets this is a constant value 3 pF,
+ * but this is different on each board setup. You need to fine
+ * tuning this value via CTRIM.
+ * CTRIM = variable capacitor setting. Resolution is 0.3 pF range is
+ * 0 pF upto 4.5 pF.
+ *
+ * Examples:
+ * atben transceiver:
+ *
+ * CL = 8 pF
+ * CX = 12 pF
+ * CPAR = 3 pF (We assume the magic constant from datasheet)
+ * CTRIM = 0.9 pF
+ *
+ * (12+0.9+3)/2 = 7.95 which is nearly at 8 pF
+ *
+ * xtal_trim = 0x3
+ *
+ * openlabs transceiver:
+ *
+ * CL = 16 pF
+ * CX = 22 pF
+ * CPAR = 3 pF (We assume the magic constant from datasheet)
+ * CTRIM = 4.5 pF
+ *
+ * (22+4.5+3)/2 = 14.75 which is the nearest value to 16 pF
+ *
+ * xtal_trim = 0xf
+ */
+ rc = at86rf230_write_subreg(lp, SR_XTAL_TRIM, xtal_trim);
+ if (rc)
+ return rc;
+
rc = at86rf230_read_subreg(lp, SR_DVDD_OK, &dvdd);
if (rc)
return rc;
@@ -1378,9 +1417,11 @@
}
static int
-at86rf230_get_pdata(struct spi_device *spi, int *rstn, int *slp_tr)
+at86rf230_get_pdata(struct spi_device *spi, int *rstn, int *slp_tr,
+ u8 *xtal_trim)
{
struct at86rf230_platform_data *pdata = spi->dev.platform_data;
+ int ret;
if (!IS_ENABLED(CONFIG_OF) || !spi->dev.of_node) {
if (!pdata)
@@ -1388,11 +1429,15 @@
*rstn = pdata->rstn;
*slp_tr = pdata->slp_tr;
+ *xtal_trim = pdata->xtal_trim;
return 0;
}
*rstn = of_get_named_gpio(spi->dev.of_node, "reset-gpio", 0);
*slp_tr = of_get_named_gpio(spi->dev.of_node, "sleep-gpio", 0);
+ ret = of_property_read_u8(spi->dev.of_node, "xtal-trim", xtal_trim);
+ if (ret < 0 && ret != -EINVAL)
+ return ret;
return 0;
}
@@ -1505,13 +1550,14 @@
struct at86rf230_local *lp;
unsigned int status;
int rc, irq_type, rstn, slp_tr;
+ u8 xtal_trim;
if (!spi->irq) {
dev_err(&spi->dev, "no IRQ specified\n");
return -EINVAL;
}
- rc = at86rf230_get_pdata(spi, &rstn, &slp_tr);
+ rc = at86rf230_get_pdata(spi, &rstn, &slp_tr, &xtal_trim);
if (rc < 0) {
dev_err(&spi->dev, "failed to parse platform_data: %d\n", rc);
return rc;
@@ -1570,7 +1616,7 @@
spi_set_drvdata(spi, lp);
- rc = at86rf230_hw_init(lp);
+ rc = at86rf230_hw_init(lp, xtal_trim);
if (rc)
goto free_dev;