Mike
I already sent a patch some time ago, it addresses this bug and
alot more. See spi-devel-general
<[EMAIL PROTECTED]>,
I am waiting for David B. to comment/apply it. If you want to see this
in 2.6.25 I suggest you remind 'David Brownell' <[EMAIL PROTECTED]>
Jocke
On Mon, 2008-03-31 at 08:04 -0500, Mike Hench wrote:
> dont write SPMODE reg unless mode changed.
> it causes SPI to go hi-z momentarily
> which can cause a spike on the CLK line
> this is a problem in MMC where /CS is held asserted
> across multiple transactions.
>
> Signed-off-by: Mike Hench <[EMAIL PROTECTED]>
>
> ---
>
> --- linux-2.6.25-rc5.orig/drivers/spi/spi_mpc83xx.c 2008-03-10
> 00:22:27.000000000 -0500
> +++ linux-2.6.25-rc5/drivers/spi/spi_mpc83xx.c 2008-03-31
> 07:37:37.000000000 -0500
> @@ -147,6 +147,7 @@
>
> if (value == BITBANG_CS_ACTIVE) {
> u32 regval =
> mpc83xx_spi_read_reg(&mpc83xx_spi->base->mode);
> + u32 regval0 = regval;
> u32 len = spi->bits_per_word;
> u8 pm;
>
> @@ -188,9 +189,16 @@
> regval |= SPMODE_PM(pm);
> }
>
> - /* Turn off SPI unit prior changing mode */
> - mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, 0);
> - mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, regval);
> + // dont write reg unless mode changed.
> + // it causes SPI to go hi-z momentarily
> + // which can cause a spike on the CLK line
> + // this is a problem in MMC where /CS is held asserted
> + // across multiple transactions.
> + if(regval != regval0) {
> + /* Turn off SPI unit prior changing mode */
> + mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode,
> 0);
> + mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode,
> regval);
> + }
> if (mpc83xx_spi->activate_cs)
> mpc83xx_spi->activate_cs(spi->chip_select, pol);
> }
>
> _______________________________________________
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> Linuxppc-dev@ozlabs.org
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>
>
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