media: isl6421: add checks for current overflow

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.

Tested on Skystar S2. Changes respect override_or option so should still work fine
on cx88 based cards which disable dynamic current limit.

Changes since v1:
v2 - fixed incorrect checking of i2c return values
v3 - fix if logic to check if dcl needs re-enabling
   - respect override_or values which aim to disable dcl
   - only do long sleep on overload if dcl enabled
   - add short sleep before re-enabling dcl
   - only check overload and potentially return EINVAL if device is on
v4 - revert v3 sleep logic changes to remove tuning delays

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jemma Denson <jdenson@gmail.com>

diff --git a/drivers/media/dvb-frontends/isl6421.c b/drivers/media/dvb-frontends/isl6421.c
index 838b42771a05812c01e2d9f388e00512240030ca..3f34878876723b81a9c7f5382a7801100b766206 100644 (file)
--- a/drivers/media/dvb-frontends/isl6421.c
+++ b/drivers/media/dvb-frontends/isl6421.c
@@ -38,35 +38,101 @@ 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:
                return -EINVAL;
        }
 
+       /*
+        * 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_DCL;
+
        isl6421->config |= isl6421->override_or;
        isl6421->config &= isl6421->override_and;
 
-       return (i2c_transfer(isl6421->i2c, &msg, 1) == 1) ? 0 : -EIO;
+       ret = i2c_transfer(isl6421->i2c, msg, 2);
+       if (ret < 0)
+               return ret;
+       if (ret != 2)
+               return -EIO;
+
+       /* Store off status now incase future commands fail */
+       isl6421->is_off = is_off;
+
+       /* On overflow, the device will try again after 900 ms (typically) */
+       if (!is_off && (buf & ISL6421_OLF1))
+               msleep(1000);
+
+       /* Re-enable dynamic current limit */
+       if ((isl6421->config & ISL6421_DCL) &&
+           !(isl6421->override_or & ISL6421_DCL)) {
+               isl6421->config &= ~ISL6421_DCL;
+
+               ret = i2c_transfer(isl6421->i2c, msg, 2);
+               if (ret < 0)
+                       return ret;
+               if (ret != 2)
+                       return -EIO;
+       }
+
+       /* Check if overload flag is active. If so, disable power */
+       if (!is_off && (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 +214,8 @@ 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;