Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 85146114 authored by Antti Palosaari's avatar Antti Palosaari Committed by Mauro Carvalho Chehab
Browse files

[media] e4000: implement DC offset correction 



I did some tests against modulator (television signal generator) and this
seems to improve sensitivity a little bit on channel I used. Used device
was able to receive transmission just as weak signal as with Windows XP.
Thanks to Jacek for donating his non-working device. I cannot ask he to
test anymore...

Reported-by: default avatarJacek Konieczny <jajcus@jajcus.net>
Signed-off-by: default avatarAntti Palosaari <crope@iki.fi>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 83453a7c

drivers/media/tuners/e4000.c

+48 −8
Original line number Diff line number Diff line
@@ -140,14 +140,12 @@ static int e4000_init(struct dvb_frontend *fe) 
	if (ret < 0)

		goto err;



	/*

	 * TODO: Implement DC offset control correctly.

	 * DC offsets has quite much effect for received signal quality in case

	 * of direct conversion tuners (Zero-IF). Surely we will now lose few

	 * decimals or even decibels from SNR...

	 */

	/* DC offset control */

	ret = e4000_wr_reg(priv, 0x2d, 0x0c);

	ret = e4000_wr_reg(priv, 0x2d, 0x1f);

	if (ret < 0)

		goto err;



	ret = e4000_wr_regs(priv, 0x70, "\x01\x01", 2);

	if (ret < 0)

		goto err;
@@ -204,7 +202,7 @@ static int e4000_set_params(struct dvb_frontend *fe) 
	struct dtv_frontend_properties *c = &fe->dtv_property_cache;

	int ret, i, sigma_delta;

	unsigned int f_VCO;

	u8 buf[5];

	u8 buf[5], i_data[4], q_data[4];



	dev_dbg(&priv->i2c->dev, "%s: delivery_system=%d frequency=%d " \

			"bandwidth_hz=%d\n", __func__,
@@ -292,6 +290,48 @@ static int e4000_set_params(struct dvb_frontend *fe) 
	if (ret < 0)

		goto err;



	/* DC offset */

	for (i = 0; i < 4; i++) {

		if (i == 0)

			ret = e4000_wr_regs(priv, 0x15, "\x00\x7e\x24", 3);

		else if (i == 1)

			ret = e4000_wr_regs(priv, 0x15, "\x00\x7f", 2);

		else if (i == 2)

			ret = e4000_wr_regs(priv, 0x15, "\x01", 1);

		else

			ret = e4000_wr_regs(priv, 0x16, "\x7e", 1);



		if (ret < 0)

			goto err;



		ret = e4000_wr_reg(priv, 0x29, 0x01);

		if (ret < 0)

			goto err;



		ret = e4000_rd_regs(priv, 0x2a, buf, 3);

		if (ret < 0)

			goto err;



		i_data[i] = (((buf[2] >> 0) & 0x3) << 6) | (buf[0] & 0x3f);

		q_data[i] = (((buf[2] >> 4) & 0x3) << 6) | (buf[1] & 0x3f);

	}



	buf[0] = q_data[0];

	buf[1] = q_data[1];

	buf[2] = q_data[3];

	buf[3] = q_data[2];

	ret = e4000_wr_regs(priv, 0x50, buf, 4);

	if (ret < 0)

		goto err;



	buf[0] = i_data[0];

	buf[1] = i_data[1];

	buf[2] = i_data[3];

	buf[3] = i_data[2];

	ret = e4000_wr_regs(priv, 0x60, buf, 4);

	if (ret < 0)

		goto err;



	/* gain control auto */

	ret = e4000_wr_reg(priv, 0x1a, 0x17);

	if (ret < 0)