On Thu, Jan 11, 2024 at 03:32:54PM -0600, David Lechner wrote: > On Thu, Jan 11, 2024 at 2:54 PM David Lechner <dlechner@xxxxxxxxxxxx> wrote: > > > (CCed) a while back when he was doing all the work he did on optimising > > > the core for uncontended uses, the thinking there was to have a > > > spi_prepare_message() (or similar) API that drivers could call and then > > > reuse the same transfer repeatedly, and even without any interface for > > > client drivers it's likely that we'd be able to take advantage of it in > > > the core for multi-transfer messages. I'd be surprised if there weren't > > > wins when the message goes over the DMA copybreak size. A much wider > > > range of hardware would be able to do this bit, for example David's case > > > was a Raspberry Pi using the DMA controller to write into the SPI > For those, following along, it looks like the RPi business was > actually a 2013 discussion with Martin Sperl [2]. Both this and [1] > discuss proposed spi_prepare_message() APIs. > [2]: https://lore.kernel.org/linux-spi/CACRpkdb4mn_Hxg=3tuBu89n6eyJ082EETkwtNbzZDFZYTHbVVg@xxxxxxxxxxxxxx/T/#u Oh, yes - sorry, I'd misremembered which optimisation effort it was associated with. Apologies.
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