On 04/04/2022 10:40, AngeloGioacchino Del Regno wrote: > Il 02/04/22 13:38, Krzysztof Kozlowski ha scritto: >> On 01/04/2022 15:50, AngeloGioacchino Del Regno wrote: >>> The syscon driver now enables the .fast_io regmap configuration when >>> the 'fast-io' property is found in a syscon node. >>> >>> Keeping in mind that, in regmap, fast_io is checked only if we are >>> not using hardware spinlocks, allow the fast-io property only if >>> there is no hwlocks reference (and vice-versa). >> >> I have doubts you need a property for this. "fast" is subjective in >> terms of hardware, so this looks more like a software property, not >> hardware. >> >> I think most of MMIOs inside a SoC are considered fast. Usually also the >> syscon/regmap consumer knows which regmap it gets, so knows that it is >> fast or not. >> > > Hello Krzysztof, > > well yes, this property is changing how software behaves - specifically, > as you've correctly understood, what regmap does. > > It's true that most of MMIOs inside a SoC are considered fast.. the word "most" is > the exact reason why I haven't proposed simply hardcoding '.fast_io = true' in > syscon, or in regmap-mmio... > There are too many different SoCs around, and I didn't want to end up breaking > anything (even if it should be unlikely, since MMIO is fast by principle). What I am proposing, is the regmap consumer knows whether access is fast or not, so it could call get_regmap() or syscon_regmap_lookup_by_phandle() with appropriate argument. Even if we stay with a DT property, I am not sure if this is an attribute of syscon but rather of a bus. Best regards, Krzysztof
