Re: [PATCH 1/2] dt-bindings: spi: dw: add cs-override property

From: Mark Brown
Date: Thu Oct 11 2018 - 09:46:44 EST


On Wed, Oct 10, 2018 at 10:21:51PM +0000, Trent Piepho wrote:

> So that's the problem! I, like everyone else I suspect, switched to
> using GPIO chip selects with this driver because of this. I narrowed

That's generally a good idea.

> it down to a CS de-assert when the bus switched from TX to RX, which of
> course makes a SPI register read fail on most devices. The TX FIFO
> would empty at this point, so that would explain it.

> Did the designers of this IP ever read a SPI device datasheet???

> Got to agree with Mark Brown, why would anyone ever want to NOT have it
> work properly? The previous behavior is not "alternate correct", it's
> Broken.

This isn't even that unusual an innovation for hardware to have, for
some reason automatic chip select management is *really* popular and
rarely helpful. It's far from the most entertaining thing I've seen
hardware do.

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