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