The auxiliary spi supports only CPHA=0 modes as the first bit is
always output to the pin before the first clock cycle. In CPHA=1
modes the first clock edge outputs the second bit hence the slave
can never read the first bit.
Also the CPHA registers switch between clocking data in/out on
rising/falling edge hence depend on the CPOL setting.
Signed-off-by: Stephan Olbrich <stephanolbrich@gmx.de>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
When using reverse polarity for clock (spi-cpol) on a device
the clock line gets altered after chip-select has been asserted
resulting in an additional clock beat, which confuses hardware.
This happens due to the fact, the the hardware was initialized
and reset at the begin and end of each transfer which results
in default state for all lines except chip-select which is
handled by the spi-subsystem as gpio-cs is used.
To avoid this situation this patch moves the setup of polarity
(spi-cpol and spi-cpha) outside of the chip-select into
prepare_message, which is run prior to asserting chip-select.
Signed-off-by: Stephan Olbrich <stephanolbrich@gmx.de>
Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
Tested-by: Martin Sperl <kernel@martin.sperl.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
The tx empty irq can be disabled when all data was copied.
This prevents unnecessary interrupts while the last bytes are sent.
Signed-off-by: Stephan Olbrich <stephanolbrich@gmx.de>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
The bitmasks for txempty and idle interrupts were interchanged.
Signed-off-by: Stephan Olbrich <stephanolbrich@gmx.de>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
Change the initialization order of the HW so that the interrupt
is only requested after the HW is initialized
Also the use of irq_of_parse_and_map is replaced by platform_get_irq.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
There are strange issues with the auxiliary spi device that result
in "lost" data in the RX path if the fifo is filled by too much
(even though the status register is checked if new data can get filled
in).
This has been observed primarily for the interrupt case.
Polling works fine, probably because the RX fifo is pulled immediately
when in the tight polling loop.
For that reason we have to limit the pending bytes to less than 15
when filling the fifo in interrupt mode.
There also was an issue returning the "wrong" last 1/2 bytes
of a transfer when the transfer is not a multiple of 3 bytes.
(this impacted polling and interrupt modes)
Also fixed an overflow in the estimation of the transfer time used
to decide if we run in interrupt or polling mode (found with the
spi-bcm2835.c driver originally).
Reported-by: Georgii Staroselskii <georgii.staroselskii@emlid.com>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
The bcm2835 has 2 auxiliary spi bus masters spi1 and spi2.
This implements the driver to enable these devices.
The driver does not implement native chip-selects but uses
the aribtrary GPIO-chip-selects provided by the spi-chipselect.
Note that this driver relies on the fact that
the clock is implemented by the clk-bcm2835-aux driver,
which enables/disables the HW block when requesting/releasing
the clock.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
