As we'll need to retrieve cached registers, make this
function explicit.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

If signal is zero, shows it as a zero, not as 0xff.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

This is part of the original driver, and adding it doesn't hurt,
so add it, to better sync the code.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

As the driver's logic uses the bit-reversed order for read,
use it as well when displaying the debug messages.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

The Realtek Kernel driver uses the second DVB-T 7MHz table instead
of the first one. Use it as well.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

On read, the bit order is inverted.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

IF is set at r820t_set_tv_standard(). So, we can't calculate
LO frequency before calling it.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

Scale used at get_if_freq and LO freq calculus is Hz.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

	[ 2255.342797] r820t 3-001a: generic_set_freq: PLL locked on frequency 725476191 Hz, gain=45
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

As this tuner can be used by analog and digital parts of the
driver, be sure that all ops that access the hardware will
be be properly locked.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

This tuner works with 2 modes: automatic gain mode and manual
gain mode. Put it into automatic mode, as we currently don't
have any API for manual gain adjustment.
The logic to allow setting the manual mode is there, as it is
just a few extra code. This way, if/when we latter add support
for setting the gain mode, the code is already there.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

Instead of a binary signal strength measure, use the tuner gain
to obtain a better estimation of the signal strength.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>

This driver was written from scratch, based on an existing driver
that it is part of rtl-sdr git tree, released under GPLv2:
	https://groups.google.com/forum/#!topic/ultra-cheap-sdr/Y3rBEOFtHug
	https://github.com/n1gp/gr-baz
	http://cgit.osmocom.org/rtl-sdr/plain/src/tuner_r820t.c
	(there are also other variants of it out there)
>From what I understood from the threads, the original driver was converted
to userspace from a Realtek tree. I couldn't find the original tree.
However, the original driver look awkward on my eyes. So, I decided to
write a new version from it from the scratch, while trying to reproduce
everything found there.
TODO:
- After locking, the original driver seems to have some routines to
  improve reception. This was not implemented here yet.
- RF Gain set/get is not implemented.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: NAntti Palosaari <crope@iki.fi>