In order to add an alternative method of DMA-based SPI transfer first we
need to detach the currently available one from the common code. Here we
move the normal DMA-based SPI transfer execution functionality into a
dedicated method. It will be utilized if either the DMA engine supports
an unlimited number SG entries or Tx-only SPI transfer is requested. But
currently just use it for any SPI transfer.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-9-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It's pointless to pass the Rx and Tx transfers DMA Tx-descriptors, since
they are used in the Tx/Rx submit method only. Instead just return the
submission status from these methods. This alteration will make the code
less complex.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-8-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
We suggest to add the dmaengine_submit() return value test for errors. It
has been unnecessary while the driver was expected to be utilized in pair
with DW DMAC. But since now the driver can be used with any DMA engine, it
might be useful to track the errors on DMA submissions so not miss them
and get into an unpredictable driver behaviour.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-7-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Indeed we can freely move the dmaengine_submit() method invocation and the
Tx and Rx busy flag setting into the DMA Tx/Rx prepare methods. Since the
Tx/Rx preparation method is now mainly used for the DMA transfers
submission, here we suggest to rename it to have the _submit_{r,t}x suffix
instead.
By having this alteration applied first we implement another code
preparation before adding the one-by-one DMA SG entries transmission,
second we now have the dma_async_tx_descriptor descriptor used locally
only in the new DMA transfers submission methods (this will be cleaned up
a bit later), third we make the generic transfer method more readable,
where now the functionality of submission, execution and wait procedures
is transparently split up instead of having a preparation, intermixed
submission/execution and wait procedures.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Checking rx_buf for being NULL and returning NULL from the Rx-channel
preparation method doesn't let us to distinguish that situation from
errors happening during the Rx SG-list preparation. So it's better to make
sure that the rx_buf not-NULL and full-duplex communication is requested
prior calling the Rx preparation method.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Mainly this is a preparation patch before adding one-by-one DMA SG entries
transmission. But logically the Tx and Rx DMA channels setup should be
performed in the dma_setup() callback anyway. So we'll move the DMA slave
channels src/dst burst lengths, address and address width configuration
from the Tx/Rx channels preparation methods to the dedicated functions and
then make sure it's called at the DMA setup stage.
Note we now make sure the return value of the dmaengine_slave_config()
method doesn't indicate an error. It has been unnecessary in case if Dw
DMAC is utilized as a DMA engine, since its device_config() callback
always returns zero (though it might change in future). But since DW APB
SSI driver now supports any DMA back-end we must make sure the DMA device
configuration has been successful before proceeding with further setups.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Since commit 46164fde6b ("spi: dw: Fix Rx-only DMA transfers") if DMA
interface is enabled, then Tx-buffer must be available in each SPI
transfer. It's required since in order to activate the incoming data
reception either DMA or CPU must be pushing data out to the SPI bus.
But the DW APB SSI DMA driver code is still left in state as if Tx-buffer
might be optional, which is no longer true. Let's fix it so an error would
be returned if no Tx-buffer detected and DMA Tx would be always
enabled.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-3-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Indeed the registers content doesn't get cleared when the SPI controller
is disabled and enabled. Max burst lengths aren't changed since the Rx and
Tx DMA channels are requested on init stage and are kept acquired until
the device is removed. Obviously SPI controller FIFO depth can't be
changed. Due to all of that we can safely move the DMA Transmit and
Receive data level registers initialization to the SPI controller DMA init
stage (when the SPI controller is being probed) instead of doing it for
each SPI transfer when dma_setup is called. This shall speed the DMA-based
SPI transfer initialization up a bit, particularly if the APB bus is
relatively slow.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112322.24585-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It turns out having a Rx DMA channel serviced with higher priority than
a Tx DMA channel is not enough to provide a well balanced DMA-based SPI
transfer interface. There might still be moments when the Tx DMA channel
is occasionally handled faster than the Rx DMA channel. That in its turn
will eventually cause the SPI Rx FIFO overflow if SPI bus speed is high
enough to fill the SPI Rx FIFO in before it's cleared by the Rx DMA
channel. That's why having the DMA-based SPI Tx interface too optimized
is the errors prone, so the commit 0b2b66514f ("spi: dw: Use DMA max
burst to set the request thresholds") though being perfectly normal from
the standard functionality point of view implicitly introduced the problem
described above. In order to fix that the Tx DMA activity is intentionally
slowed down by limiting the SPI Tx FIFO depth with a value twice bigger
than the Tx burst length calculated earlier by the
dw_spi_dma_maxburst_init() method.
Fixes: 0b2b66514f ("spi: dw: Use DMA max burst to set the request thresholds")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20200721203951.2159-1-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It's better to understand what bits are set for DMA and for IRQ handling
in mid_spi_dma_setup() if they are grouped accordingly. Thus,
refactor mid_spi_dma_setup() to separate DMA and IRQ configuration.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200529183150.44149-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
The 2afccbd283 ("spi: dw: Discard static DW DMA slave structures")
did a clean up of global variables, which is fine, but messed up with
the carefully provided information in the custom DMA slave structures.
There reader can find an assignment of the DMA request lines in use.
Partially revert the above mentioned commit to restore readability
and maintainability of the code.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200529183150.44149-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Since from now the former Intel MID platform layer is used as a generic
DW SPI DMA module, let's alter the internal methods naming to be
DMA-related instead of having the "mid_" prefix.
Co-developed-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-14-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
This is a preparation patch before adding the DW DMA support into the
DW SPI MMIO driver. We need to unpin the Non-DMA-specific code from the
intended to be generic DW APB SSI DMA code. This isn't that hard,
since the most part of the spi-dw-mid.c driver in fact implements a
generic DMA interface for the DW SPI controller driver. The only Intel
MID specifics concern getting the max frequency from the MRST Clock
Control Unit and fetching the DMA controller channels from
corresponding PCIe DMA controller. Since first one is related with the
SPI interface configuration we moved it' implementation into the
DW PCIe-SPI driver module. After that former spi-dw-mid.c file
can be just renamed to be the DW SPI DMA module optionally compiled in to
the DW APB SSI core driver.
Co-developed-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-11-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Serge Semin