On Wed, Mar 04, 2026 at 08:38:17AM -0600, Tom Rini wrote: > On Wed, Mar 04, 2026 at 10:41:57AM +0800, Ng, Boon Khai wrote: > > > > > > > > Thanks. And can we reasonably follow what Linux does here instead? > > > > > > > We don't have ACPI in our devices, instead, i think that can be replaced > > with DTS. > > I thought Conor said it could be auto-detected still, without ACPI, in > Linux?
The controller capabilities are auto-detected. This has nothing to do with ACPI AFAICT, I don't know why that was brought up. What it detects is not an exact value though, the detected capability is the max of a range. On Linux, the spi controller driver advertises the range it supports. The spi device struct carries the bits_per_word that it wants to use, and the controller driver looks into that struct to figure out what supported bits_per_word setting to use in the transfer function. It's not as simple as just reading the register in the controller and setting the U-Boot drivers bits_per_word to the value, but I don't see why U-Boot couldn't do what Linux does here. If you search in spi-dw-core for bits_per_word, you should be able to get a grasp of how it works.
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