linux-kernel - [PATCH v6 0/2] spi: support inter-word delays

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Message-Id: <20190130084005.18649-1-jonas@norrbonn.se>
Date:   Wed, 30 Jan 2019 09:40:03 +0100
From:   Jonas Bonn <jonas@...rbonn.se>
To:     linux-kernel@...r.kernel.org
Cc:     Jonas Bonn <jonas@...rbonn.se>
Subject: [PATCH v6 0/2] spi: support inter-word delays

Changed in v6:
* Changed name of field word_delay_us to word_delay_usecs as per
  suggestion in patch review
* Add Nicolas' ACK to spi-atmel patch

Changed in v5:
* Rebased on linux-next
* Fixed up Atmel patch to simplify register setting

Changed in v4:
* Rename word_delay to word_delay_us and slot it in _beside_ the
  existing word_delay parameter in spi_transfer (see commit message for
  more info).
* Add code to __spi_validate to make sure transfer and device align with
  respect to the word_delay_us parameter

Changed in v3:
* Drop setting of inter-word delay via device tree

Changed in v2:
* Fix atmel-spi driver to not unconditionally set minimal delay if no
  delay is required (erroneous clamping)

This short series adds support for SPI inter-word delays and configures
the spi-atmel driver to honour the setting.

Some SPI slaves are so slow that they are unable to keep up even at the
SPI controller's lowest available clock frequency.  I have such a
configuration where an AVR-based SPI slave is unable to feed the SPI bus
fast enough even the SPI master runs at the lowest possible clock speed.

Jonas Bonn (2):
  spi: support inter-word delay requirement for devices
  spi-atmel: support inter-word delay

 drivers/spi/spi-atmel.c | 11 ++++++-----
 drivers/spi/spi.c       |  5 +++++
 include/linux/spi/spi.h |  6 ++++++
 3 files changed, 17 insertions(+), 5 deletions(-)

-- 
2.19.1