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Commit ccdaeb2b authored by Alexander Aring's avatar Alexander Aring Committed by Marcel Holtmann
Browse files

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: default avatarAlexander Aring <alex.aring@gmail.com>
Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
parent aaa1c4d2

Documentation/devicetree/bindings/net/ieee802154/at86rf230.txt

+3 −0
Original line number Diff line number Diff line
@@ -11,6 +11,8 @@ Required properties: 
Optional properties:

  - reset-gpio:		GPIO spec for the rstn pin

  - sleep-gpio:		GPIO spec for the slp_tr pin

  - xtal-trim:		u8 value for fine tuning the internal capacitance

			arrays of xtal pins: 0 = +0 pF, 0xf = +4.5 pF



Example:
@@ -20,4 +22,5 @@ Example: 
		reg = <0>;

		interrupts = <19 1>;

		interrupt-parent = <&gpio3>;

		xtal-trim = /bits/ 8 <0x06>;

	};

drivers/net/ieee802154/at86rf230.c

+50 −4
Original line number Diff line number Diff line
@@ -1315,7 +1315,7 @@ static struct at86rf2xx_chip_data at86rf212_data = { 
	.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 @@ static int at86rf230_hw_init(struct at86rf230_local *lp) 
	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_hw_init(struct at86rf230_local *lp) 
}



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 @@ at86rf230_get_pdata(struct spi_device *spi, int *rstn, int *slp_tr) 


		*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 @@ static int at86rf230_probe(struct spi_device *spi) 
	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 @@ static int at86rf230_probe(struct spi_device *spi) 


	spi_set_drvdata(spi, lp);



	rc = at86rf230_hw_init(lp);

	rc = at86rf230_hw_init(lp, xtal_trim);

	if (rc)

		goto free_dev;

include/linux/spi/at86rf230.h

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ struct at86rf230_platform_data { 
	int rstn;

	int slp_tr;

	int dig2;

	u8 xtal_trim;

};



#endif