The requested bit rate can be outside the range supported by the driver.
The maximum bit rate this driver supports at the moment is 400Khz.

If the requested bit rate is larger than the maximum supported by the
driver, set the bitrate to the maximum supported before bitrate_khz is
calculated.

Maximum speed supported by the driver can be increased to 1Mhz by
adding support for "fast plus mode" in the future.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Clear line status and all generated interrupts from the interrupt
status register before starting a transfer, as we may have
unserviced interrupts from previous transfers that might be
handled in the context of the new transfer.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

i2c->line_status accumulates the line status bits that have been seen
with each interrupt. As we're only interested in that bit from the
current interrupt, refer to line_status (the argument to img_i2c_auto)
instead of i2c->line_status.
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Currently, after determining the minimum value for the High period
(TCKH) the remainder of the internal clock pulses is set as the Low
period (TCKL). This causes the i2c clock duty cycle to be much less
than 50%.

Modify the starting position to TCKH and TCKL at 50% of the internal
clock, and adjusts the TCKH and TCKL values from there should the
minimum value for TCKL not be met. This results in duty cycles closer
to 50%.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Using % can be slow depending on the architecture.

Using DIV_ROUND_UP is nicer and more efficient way to do it.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Move scb_wr_rd_fence to before reading from fifo and writing to
fifo to make sure the the first read/write is done after the required
number of cycles.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

The code to read from the master read fifo, and write to the master
write fifo, checks a bit in an SCB register before every byte to
ensure that the fifo is not full (write fifo) or empty (read fifo).
Due to clock domain crossing inside the SCB block the updated value
of this bit is only visible after 2 cycles.

The scb_wr_rd_fence() function does 2 dummy writes (to the read-only
revision register), and it's called before reading from or writing to the
fifos to ensure that subsequent reads of the fifo status bits do not read
stale values.

As the 2 dummy writes are required in all versions of the ip, the version
check is dropped.

Fixes: commit 27bce457 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: NSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Return type of wait_for_completion_timeout is unsigned long not int.
Appropriately typed/named variable are added and assignment fixed up.
Signed-off-by: NNicholas Mc Guire <hofrat@osadl.org>
Acked-by: NJames Hogan <james.hogan@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Add support for the IMG I2C Serial Control Bus (SCB) found on the
Pistachio and TZ1090 SoCs.
Reviewed-by: NAndrew Bresticker <abrestic@chromium.org>
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
[Ezequiel: code cleaning and rebasing]
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@imgtec.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>