Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1273854

Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word wait cycles using the SPI Wait Clock Register

Show all headers | View raw

Hi Julian,

2015-11-19 23:59 GMT+01:00 Julian Calaby <julian.calaby@gmail.com>:
> Should you possibly hide the 3 clock periods from the user?
>
> I.e. they set whatever they want for the wdelay, we set it to the
> closest number we can that's greater or equal to what they ask for.

That's a good idea and much better than having to remember to subtract
3 cycles from the desired wait time!

But it would mean that this magic number becomes part of the driver
code. I have found no official documentation that mentions those
additional cycles. While I have checked many different transmission
speeds using both CDR1 and CDR2 divider configurations, there is still
the possibility that the behaviour changes with weird SPI module
configurations... And I've only tested it on A20 hardware. So it would
be great if somebody else with access to A10 hardware and an
oscilloscope could check if we have a consistent 3 cycle overhead.

Cheers,

   Marcus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] spi: dts: sun4i: Add support for inter-word wait cycles Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-19 17:00 +0100
  [PATCH] spi: dts: sun4i: Add support for inter-word wait cycles using the SPI Wait Clock Register Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-19 17:00 +0100
    Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Julian Calaby <julian.calaby@gmail.com> - 2015-11-20 00:00 +0100
      Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-20 09:50 +0100
        Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Julian Calaby <julian.calaby@gmail.com> - 2015-11-20 11:20 +0100
          Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-20 15:00 +0100
            Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for  inter-word wait cycles using the SPI Wait Clock Register Rob Herring <robh@kernel.org> - 2015-11-20 17:20 +0100
              Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-20 17:50 +0100
                Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for  inter-word wait cycles using the SPI Wait Clock Register Maxime Ripard <maxime.ripard@free-electrons.com> - 2015-11-22 20:50 +0100
                Re: [linux-sunxi] [PATCH] spi: dts: sun4i: Add support for inter-word  wait cycles using the SPI Wait Clock Register Marcus Weseloh <mweseloh42@gmail.com> - 2015-11-23 10:20 +0100
    Re: [PATCH] spi: dts: sun4i: Add support for inter-word wait cycles  using the SPI Wait Clock Register Rob Herring <robh@kernel.org> - 2015-11-20 17:10 +0100

csiph-web