Re: [PATCH RFC] media: isl6421: add checks for current overflow

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Hi Mauro,

Just tried this on my card - unfortunately the patch as is doesn't work.

On 13/08/17 13:10, Mauro Carvalho Chehab wrote:
This Kaffeine's BZ:
	https://bugs.kde.org/show_bug.cgi?id=374693

affects SkyStar S2 PCI DVB-S/S2 rev 3.3 device. It could be due to
a Kernel bug.

While checking the Isil 6421, comparing with its manual, available at:

	http://www.intersil.com/content/dam/Intersil/documents/isl6/isl6421a.pdf

It was noticed that, if the output load is highly capacitive, a different approach
is recomended when energizing the LNBf.

Also, it is possible to detect if a current overload is happening, by checking an
special flag.

Add support for it.

Compile-tested only.

Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
---
  drivers/media/dvb-frontends/isl6421.c | 72 +++++++++++++++++++++++++++++++++--
  1 file changed, 68 insertions(+), 4 deletions(-)

diff --git a/drivers/media/dvb-frontends/isl6421.c b/drivers/media/dvb-frontends/isl6421.c
index 838b42771a05..47a7e559cef2 100644
--- a/drivers/media/dvb-frontends/isl6421.c
+++ b/drivers/media/dvb-frontends/isl6421.c
@@ -38,25 +38,43 @@ struct isl6421 {
  	u8			override_and;
  	struct i2c_adapter	*i2c;
  	u8			i2c_addr;
+	bool			is_off;
  };
static int isl6421_set_voltage(struct dvb_frontend *fe,
  			       enum fe_sec_voltage voltage)
  {
+	int ret;
+	u8 buf;
+	bool is_off;
  	struct isl6421 *isl6421 = (struct isl6421 *) fe->sec_priv;
-	struct i2c_msg msg = {	.addr = isl6421->i2c_addr, .flags = 0,
-				.buf = &isl6421->config,
-				.len = sizeof(isl6421->config) };
+	struct i2c_msg msg[2] = {
+		{
+		  .addr = isl6421->i2c_addr,
+		  .flags = 0,
+		  .buf = &isl6421->config,
+		  .len = 1,
+		}, {
+		  .addr = isl6421->i2c_addr,
+		  .flags = I2C_M_RD,
+		  .buf = &buf,
+		  .len = 1,
+		}
+
+	};
isl6421->config &= ~(ISL6421_VSEL1 | ISL6421_EN1); switch(voltage) {
  	case SEC_VOLTAGE_OFF:
+		is_off = true;
  		break;
  	case SEC_VOLTAGE_13:
+		is_off = false;
  		isl6421->config |= ISL6421_EN1;
  		break;
  	case SEC_VOLTAGE_18:
+		is_off = false;
  		isl6421->config |= (ISL6421_EN1 | ISL6421_VSEL1);
  		break;
  	default:
@@ -66,7 +84,51 @@ static int isl6421_set_voltage(struct dvb_frontend *fe,
  	isl6421->config |= isl6421->override_or;
  	isl6421->config &= isl6421->override_and;
- return (i2c_transfer(isl6421->i2c, &msg, 1) == 1) ? 0 : -EIO;
+	/*
+	 * If LNBf were not powered on, disable dynamic current limit, as,
+	 * according with datasheet, highly capacitive load on the output may
+	 * cause a difficult start-up.
+	 */
+	if (isl6421->is_off && !is_off)
+		isl6421->config |= ISL6421_EN1;
+
+	ret = i2c_transfer(isl6421->i2c, msg, 2);
+	if (ret < 0)
+		return ret;
+	if (ret != 1)
+		return -EIO;

This needs to check ret != 2

+
+	isl6421->is_off = is_off;
+
+	/* On overflow, the device will try again after 900 ms (typically) */
+	if (isl6421->is_off && (buf & ISL6421_OLF1))
+		msleep(1000);
+
+	if (isl6421->is_off && !is_off) {
+		isl6421->config &= ~ISL6421_EN1;
+
+		ret = i2c_transfer(isl6421->i2c, msg, 2);
+		if (ret < 0)
+			return ret;
+		if (ret != 1)
+			return -EIO;
+	}

Same again

+
+	/* Check if overload flag is active. If so, disable power */
+	if (buf & ISL6421_OLF1) {
+		isl6421->config &= ~(ISL6421_VSEL1 | ISL6421_EN1);
+		ret = i2c_transfer(isl6421->i2c, msg, 1);
+		if (ret < 0)
+			return ret;
+		if (ret != 1)
+			return -EIO;
+		isl6421->is_off = true;
+
+		dev_warn(&isl6421->i2c->dev,
+			 "Overload current detected. disabling LNBf power\n");
+		return -EINVAL;
+	}
+	return 0;
  }
static int isl6421_enable_high_lnb_voltage(struct dvb_frontend *fe, long arg)
@@ -148,6 +210,8 @@ struct dvb_frontend *isl6421_attach(struct dvb_frontend *fe, struct i2c_adapter
  		return NULL;
  	}
+ isl6421->is_off = true;
+
  	/* install release callback */
  	fe->ops.release_sec = isl6421_release;


Once I changed these it worked fine - I can still tune in with this patch even switching from H to V. I've no idea if this fixes the bug logged in kaffeine though as I haven't seen it.


Jemma.




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