On Wed, 2018-10-10 at 13:34 +0300, Talel Shenhar wrote: > > On Wed, Oct 10, 2018 at 10:08:12AM +0300, Talel Shenhar wrote: > > > > > The dw spi controller has an auto-deselect of Chip-Select, in > > > case there is > > > no data inside the Tx FIFO. While working on platforms with > > > Alpine chips, > > > > Why would we ever want to use this behaviour? It will be broken > > for any > > non-trivial SPI message such as those made with multiple transfers > > anyway. Why not just unconditionally control it manually? > > Thank you for your prompt response. > > This behavior (auto-deselect of Chip-Select) is the default behavior > of dw spi controller hw. > On Alpine chip there is additional behavior added to the dw spi > controller hw that allows the sw to disable this behavior. > This patch allows the dw driver to enable this hw workaround and add > the needed sw manual control for it. In particular, that would have been an incompatible change and would render the hardware non-function with existing drivers. By making it opt-in, old drivers work.... as long as the FIFO doesn't stall in the middle of a transaction, which no worse than with the "standard" DW implementation anyway.
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