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  1. 11 Mar, 2019 1 commit
    • Chris Lesiak's avatar
      spi: Fix zero length xfer bug · 5442dcaa
      Chris Lesiak authored 
      This fixes a bug for messages containing both zero length and
unidirectional xfers.

The function spi_map_msg will allocate dummy tx and/or rx buffers
for use with unidirectional transfers when the hardware can only do
a bidirectional transfer.  That dummy buffer will be used in place
of a NULL buffer even when the xfer length is 0.

Then in the function __spi_map_msg, if he hardware can dma,
the zero length xfer will have spi_map_buf called on the dummy
buffer.

Eventually, __sg_alloc_table is called and returns -EINVAL
because nents == 0.

This fix prevents the error by not using the dummy buffer when
the xfer length is zero.
Signed-off-by: default avatarChris Lesiak <chris.lesiak@licor.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
      5442dcaa
  3. 04 Mar, 2019 1 commit
  5. 22 Feb, 2019 2 commits
  7. 20 Feb, 2019 2 commits
  9. 19 Feb, 2019 2 commits
  11. 13 Feb, 2019 4 commits
  13. 12 Feb, 2019 3 commits
  15. 08 Feb, 2019 3 commits
  17. 06 Feb, 2019 14 commits
  19. 30 Jan, 2019 2 commits
    • Jonas Bonn's avatar
      spi-atmel: support inter-word delay · 473a78a7
      Jonas Bonn authored 
      If the SPI slave requires an inter-word delay, configure the DLYBCT
register accordingly.

Tested on a SAMA5D2 board (derived from SAMA5D2-Xplained reference
board).
Signed-off-by: default avatarJonas Bonn <jonas@norrbonn.se>
Acked-by: default avatarNicolas Ferre <nicolas.ferre@microchip.com>
CC: Nicolas Ferre <nicolas.ferre@microchip.com>
CC: Mark Brown <broonie@kernel.org>
CC: Alexandre Belloni <alexandre.belloni@bootlin.com>
CC: Ludovic Desroches <ludovic.desroches@microchip.com>
CC: linux-spi@vger.kernel.org
CC: linux-arm-kernel@lists.infradead.org
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
      473a78a7
    • Jonas Bonn's avatar
      spi: support inter-word delay requirement for devices · b7bb367a
      Jonas Bonn authored 
      Some devices are slow and cannot keep up with the SPI bus and therefore
require a short delay between words of the SPI transfer.

The example of this that I'm looking at is a SAMA5D2 with a minimum SPI
clock of 400kHz talking to an AVR-based SPI slave.  The AVR cannot put
bytes on the bus fast enough to keep up with the SoC's SPI controller
even at the lowest bus speed.

This patch introduces the ability to specify a required inter-word
delay for SPI devices.  It is up to the controller driver to configure
itself accordingly in order to introduce the requested delay.

Note that, for spi_transfer, there is already a field word_delay that
provides similar functionality.  This field, however, is specified in
clock cycles (and worse, SPI controller cycles, not SCK cycles); that
makes this value dependent on the master clock instead of the device
clock for which the delay is intended to provide some relief.  This
patch leaves this old word_delay in place and provides a time-based
word_delay_us alongside it; the new field fits in the struct padding
so struct size is constant.  There is only one in-kernel user of the
word_delay field and presumably that driver could be reworked to use
the time-based value instead.

The time-based delay is limited to 8 bits as these delays are intended
to be short.  The SAMA5D2 that I've tested this on limits delays to a
maximum of ~100us, which is already many word-transfer periods even at
the minimum transfer speed supported by the controller.
Signed-off-by: default avatarJonas Bonn <jonas@norrbonn.se>
CC: Mark Brown <broonie@kernel.org>
CC: Rob Herring <robh+dt@kernel.org>
CC: Mark Rutland <mark.rutland@arm.com>
CC: linux-spi@vger.kernel.org
CC: devicetree@vger.kernel.org
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
      b7bb367a
  21. 29 Jan, 2019 4 commits
  23. 28 Jan, 2019 2 commits
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