On Fri, Jul 24, 2015 at 07:37:16AM +0200, Lars Persson wrote:
> This reverts commit 232a5adc5199 ("spi: bitbang: only toggle
> bitchanges") because it breaks bitbanged SPI on our MIPS system. I
> found two problems with the patch:
> - oldbit must initially be computed from bit position 7, 15 or 31 of
> word depending on the value of bits.
This might be a real issue but fixing it does not require a revert.
> - The optimization also does not eliminate consecutive ones because
> the compare of 1<<31 and 1 will be false (a bool only takes values 0
> or 1).
No, any non-zero value is true in C. I assume you're talking about
this section of the diff:
> - if ((flags & SPI_MASTER_NO_TX) == 0) {
> - if ((word & (1 << 31)) != oldbit) {
> - setmosi(spi, word & (1 << 31));
> - oldbit = word & (1 << 31);
which looks fine - we see if the top bit is the same as the last top bit
we wrote, if it isn't we update the value output and record what we just
wrote.
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