linux-kernel - [PATCH v2 0/2] Add support for components requiring trailing clock after transfer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 Feb 2022 16:15:44 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Pratyush Yadav <p.yadav@...com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: [PATCH v2 0/2] Add support for components requiring trailing clock after transfer

Some components require a few clock cycles with chipselect off before
or/and after the data transfer done with CS on.

Typically IDT 801034 QUAD PCM CODEC datasheet states "Note *: CCLK
should have one cycle before CS goes low, and two cycles after
CS goes high".

The cycles "before" are implicitely provided by all previous activity
on the SPI bus. But the cycles "after" must be provided in order to
achieve the SPI transfer.

In order to use that kind of component, implement a new option for
SPI slaves in order to implement trailing clock of a given number of
bits with ChipSelect off at the end of the transfer.

This is based on a discussion we had a few years ago, see
https://lore.kernel.org/linux-spi/20160824112701.GE22076@sirena.org.uk/

IDT 801034 QUAD PCM CODEC datasheet can be found at
https://www.renesas.com/eu/en/document/dst/821034-data-sheet?language=en&r=24763

Changes in v2:
- Provide the number of wanted clock cycles instead of just a bool. 

Christophe Leroy (2):
  spi: Add optional number of additional clock cycles to be generated
  spi: fsl-spi: Implement trailing bits

 .../bindings/spi/spi-peripheral-props.yaml    |  5 +++++
 drivers/spi/spi-fsl-spi.c                     | 21 +++++++++++++++++--
 drivers/spi/spi.c                             |  7 +++++--
 include/linux/spi/spi.h                       |  1 +
 4 files changed, 30 insertions(+), 4 deletions(-)

-- 
2.34.1