dvb-frontends/cxd2841er: require STATE_ACTIVE_* for agc readout

From: Daniel Scheller <[email protected]>

When the demod driver puts the demod into sleep or shutdown state and it's status is then polled e.g. via "dvb-fe-tool -m", i2c errors are printed to the kernel log. If the last delsys was DVB-T/T2:

cxd2841er: i2c wr failed=-5 addr=6c reg=00 len=1
cxd2841er: i2c rd failed=-5 addr=6c reg=26

and if it was DVB-C:

cxd2841er: i2c wr failed=-5 addr=6c reg=00 len=1
cxd2841er: i2c rd failed=-5 addr=6c reg=49

This happens when read_status unconditionally calls into the read_signal_strength() function which triggers the read_agc_gain_*() functions, where these registered are polled.

This isn't a critical thing since when the demod is active again, no more such errors are logged, however this might make users suspecting defects.

Fix this by requiring STATE_ACTIVE_* in priv->state. If it isn't in any active state, additionally set the strength scale to NOT_AVAILABLE.

Signed-off-by Daniel Scheller <[email protected]>

---
V2/follow-up to https://patchwork.linuxtv.org/patch/42061/, changed as requested. Tested, working fine (ie. no "false" i2c failures).

 drivers/media/dvb-frontends/cxd2841er.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

drivers/media/dvb-frontends/cxd2841er.c +4 -2

index 08f67d60a7d9..12bff778c97f 100644
@@ -3279,7 +3279,10 @@ static int cxd2841er_get_frontend(struct dvb_frontend *fe,
        else if (priv->state == STATE_ACTIVE_TC)
                cxd2841er_read_status_tc(fe, &status);
 
-       cxd2841er_read_signal_strength(fe);
+       if (priv->state == STATE_ACTIVE_TC || priv->state == STATE_ACTIVE_S)
+               cxd2841er_read_signal_strength(fe);
+       else
+               p->strength.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
 
        if (status & FE_HAS_LOCK) {
                cxd2841er_read_snr(fe);
--

2.13.0