cx18: Reduce number of mmio read retries to improve performance.  Experiments
have shown 2 things: read retries never improve the result of a suspect mmio
read from the CX23418 (the result stays all 0xff's), and that most of the
suspected read failures are actually proper reads of values that should be
all 0xff's.  This change reduces the number of read retries and keeps the
count separate from write retries.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Fix write retries for registers that always change - part 2.
Some registers, especially interrupt related ones, will never read
back the value just written.  Modified interrupt register readback
checks to make sure the intended effect was achieved.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Disable write retries for registers that always change - part 1.
Interrupt related registers will likely not read back the value we just wrote.
Disable retries for these registers for now to avoid accidently discarding
interrupts.  More intelligent read back verification criteria are needed for
these and other registers (e.g. GPIO line registers), which will be addressed in
subsequent changes.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Add default behavior of checking and retrying PCI MMIO accesses.
The concept of checking and retrying PCI MMIO accesses for better reliability
in older motherboards was suggested by Steve Toth <stoth@linuxtv.org>.  This
change implements MMIO retries and the retry_mmio module parameter that is
enabled by default.  Limited experiments have shown this is more reliable than
the mmio_ndelay parameter.  mmio_ndelay has insignificant effect with retries
enabled.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Increment u8 pointers not void pointers.  Incrementing void pointers
is dubious and the real intent in cx18_memcpy_fromio() and cx18_memset_io() is
to increment by bytes, so use u8 pointers instead.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Throttle mmio to/from the CX23418 so boards work in older systems.  The
CX23418 couldn't reliably handle mmio at the rate at which the cx18 driver was
attempting to access the chip.  The PCI bridge arrangements and settings on
modern motherboards still allowed the CX23418 to work OK, but it didn't work
well on many older motherboards: mysterious I2C errors, firmware loading errors,
etc.  This patch adds a throttle to *all* mmio access to the CX23418.  It
defaults to a delay of 31 ns, but is adjustable by the mmio_ndelay module parm.
My HVR-1600 and Raptor PAL/SECAM card now function for analog capture on a
motherboard with an Intel 82810E Northbridge and 82801AA Southbridge.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

cx18: Create cx18_ specific wrappers for all pci mmio accessesors.  This is a
first step in instrumenting all CX23418 PCI bus IO, to debug problems with
accessing the CX23418's PCI memory mapped IO.
Signed-off-by: NAndy Walls <awalls@radix.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>