spi: rzv2m-csi: Add target mode support

The CSI IP found inside the Renesas RZ/V2M SoC supports
both SPI host and SPI target roles.

When working in target mode, the CSI IP has the option
of using its Slave Selection (SS) pin to enable TX and RX
operations. Since the SPI target cannot control the clock,
when working as target it's best not to stop operations
during a transfer, as by doing so the IP will not send or
receive data, regardless of clock and active level on pin SS.
A side effect from not stopping operations is that the RX
FIFO needs to be flushed, word by word, when RX data needs
to be discarded.

Finally, when in target mode timings are tighter, as missing a
deadline translates to errors being thrown, resulting in
aborting the transfer. In order to speed things up, we can
avoid waiting for the TX FIFO to be empty, we can just wait
for the RX FIFO to contain at least the number of words that
we expect.

Add target support to the currently existing CSI driver.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Link: https://lore.kernel.org/r/20230927162508.328736-3-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: switch to use devm_spi_alloc_host()

Switch to use modern name function devm_spi_alloc_host().

No functional changed.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230818093154.1183529-16-yangyingliang@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Make use of device_set_node

Use device_set_node instead of assigning controller->dev.of_node
directly because it also sets the firmware node.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230718192453.543549-5-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Get rid of the x_trg{_words} tables

Table x_trg can be replaced with ilog2(), and table x_trg_words
can be replaced with rounddown_pow_of_two().
Replace the tables usage with the corresponding macros.
While at it, remove a couple of unnecessary empty lines.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230718192453.543549-4-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Improve data types, casting and alignment

"unsigned int" is more appropriate than "int" for the members
of "struct rzv2m_csi_priv".
Using void* rather than u8* for txbuf and rxbuf allows for
the removal of some type casting.
Remove the unnecessary casting of "data" to "struct rzv2m_csi_priv*"
in function "rzv2m_csi_irq_handler".
Also, members "bytes_per_word" and "errors" introduce gaps
in the structure.
Adjust "struct rzv2m_csi_priv" and its members usage accordingly.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Suggested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230718192453.543549-3-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Squash timing settings into one statement

Register CLKSEL hosts the configuration for both clock polarity
and data phase, and both values can be set in one write operation.

Squash the clock polarity and data phase register writes into
one statement, for efficiency.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230718192453.543549-2-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Replace unnecessary ternary operators

The ternary operators used to initialize tx_completed and rx_completed
are not necessary, replace them with a better implementation.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-6-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Leave readl_poll_timeout calls for last

Both rzv2m_csi_sw_reset and rzv2m_csi_start_stop_operation
call into readl_poll_timeout upon a certain condition, and
return 0 otherwise.
Flip the logic to improve readability.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-5-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Rework CSI_CKS_MAX definition

Clock "csiclk" gets divided by 2 * CSI_CLKSEL_CKS in order to generate
the serial clock (output from master), with CSI_CLKSEL_CKS ranging from
0x1 (that means "csiclk" is divided by 2) to 0x3FFF ("csiclk" is divided
by 32766). CSI_CKS_MAX is used for referring to the setting
corresponding to the maximum frequency divider.
Value 0x3FFF for CSI_CKS_MAX doesn't really means much to the reader
without an explanation and a more readable definition.

Add a comment with a meaningful description and also replace value
0x3FFF with the corresponding GENMASK, to make it very clear what the
macro means.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-4-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Adopt HZ_PER_MHZ for max spi clock

Make use of HZ_PER_MHZ for CSI_MAX_SPI_SCKO to make it clear
what its value means.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-3-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Add missing include

Add missing include of bits.h file.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-2-fabrizio.castro.jz@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: rzv2m-csi: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new() which already returns void. Eventually after all drivers
are converted, .remove_new() is renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230707071119.3394198-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: Add support for Renesas CSI

The RZ/V2M SoC comes with the Clocked Serial Interface (CSI)
IP, which is a master/slave SPI controller.

This commit adds a driver to support CSI master mode.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Link: https://lore.kernel.org/r/Message-Id: <20230622113341.657842-4-fabrizio.castro.jz@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>