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tegra114_spi.c

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    • Forked from Reform / reform-boundary-uboot
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    • Yen Lin's avatar
      60acde43
      spi: tegra: clear RDY bit prior to every transfer · 60acde43
      Yen Lin authored 
      
The RDY bit indicates that a transfer is complete. This needs to be
cleared by SW before every single HW transaction, rather than only
at the start of each SW transaction (those being made up of n HW
transactions).

It seems that earlier HW may have cleared this bit autonomously when
starting a new transfer, and hence this code was not needed in practice.
However, this is generally a good idea in all cases. In Tegra124, the
HW behaviour appears to have changed, and SW must explicitly clear this
bit. Otherwise, SW will believe that transfers have completed when they
have not, and may e.g. read stale data from the RX FIFO.

Signed-off-by: default avatarYen Lin <yelin@nvidia.com>
[swarren, rewrote commit description, unified duplicate RDY clearing code
and moved it right before the start of the HW transaction, unconditionally
exit loop after reading RX data, rather than checking if TX FIFO is empty,
since it is guaranteed to be]
Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
Reviewed-by: default avatarJagannadha Sutradharudu Teki <jaganna@xilinx.com>
      60acde43
      History
      spi: tegra: clear RDY bit prior to every transfer
      Yen Lin authored 
      
The RDY bit indicates that a transfer is complete. This needs to be
cleared by SW before every single HW transaction, rather than only
at the start of each SW transaction (those being made up of n HW
transactions).

It seems that earlier HW may have cleared this bit autonomously when
starting a new transfer, and hence this code was not needed in practice.
However, this is generally a good idea in all cases. In Tegra124, the
HW behaviour appears to have changed, and SW must explicitly clear this
bit. Otherwise, SW will believe that transfers have completed when they
have not, and may e.g. read stale data from the RX FIFO.

Signed-off-by: default avatarYen Lin <yelin@nvidia.com>
[swarren, rewrote commit description, unified duplicate RDY clearing code
and moved it right before the start of the HW transaction, unconditionally
exit loop after reading RX data, rather than checking if TX FIFO is empty,
since it is guaranteed to be]
Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
Reviewed-by: default avatarJagannadha Sutradharudu Teki <jaganna@xilinx.com>
    TODO.md 2.34 KiB

    MNT Reform: Operator Manual

    TOC

    • Preface
    • List of existing manuals / references / online communications channels
    • Safety / Hazards / Warnings
    • Quickstart
      • How to unwrap, plug in, turn on
      • First steps in Debian GNU/Linux
      • Important functions of the default sway-based desktop
        • Windows and workspaces
        • Display brightness
        • CPU/IO/Mem meter
        • Network
        • Audio
        • Date and time
      • (maybe) functions of the alternative GNOME desktop
    • Writing a small game/program
      • Creating graphics
      • Making sound
      • Putting it all together
    • Software recommendations
      • List of tested productivity applications (creative, office)
      • List of tested communication programs (email, chat, voip)
      • List of tested games
      • List of tested tools
    • Reference
      • Electronics
        • Schematics
        • Short explanation of important chips/parts
      • Mechanical
        • Diagram/drawings of mechanical parts
        • Explanation of what connects to what / which screw goes where
      • Common Problems
      • Maintenance
    • Credits / Thanks

    Tech

    • Sphinx worked well as a generator for the old handbook. Probably we can use it again. I might rather go with markdown than with RSt this time, but this is up for discussion. I'm also OK with looking around for another tool that can do PDF layout.
    • We don't have a printing service selected yet, and should do it soon.
    • The print format can be unusual, like A4. Ideas welcome.
    • We organize on here.

    Assets

    • Logo
    • Type
    • Graphics

    Style

    Resources