On Wed, 2022-12-07 at 10:48 +0100, AngeloGioacchino Del Regno wrote: > Il 07/12/22 03:00, Xiangsheng Hou (侯祥胜) ha scritto: > > Hi Angelo, > > > > On Tue, 2022-12-06 at 13:19 +0100, AngeloGioacchino Del Regno > > wrote: > > > > > > diff --git > > > > > > a/Documentation/devicetree/bindings/spi/mediatek,spi- > > > > > > mtk-snfi.yaml > > > > > > b/Documentation/devicetree/bindings/spi/mediatek,spi- > > > > > > mtk-snfi.yaml > > > > > > index bab23f1b11fd..6e6ff8d73fcd 100644 > > > > > > --- a/Documentation/devicetree/bindings/spi/mediatek,spi- > > > > > > mtk- > > > > > > snfi.yaml > > > > > > +++ b/Documentation/devicetree/bindings/spi/mediatek,spi- > > > > > > mtk- > > > > > > snfi.yaml > > > > > > @@ -45,6 +45,13 @@ properties: > > > > > > description: device-tree node of the accompanying > > > > > > ECC > > > > > > engine. > > > > > > $ref: /schemas/types.yaml#/definitions/phandle > > > > > > > > > > > > + mediatek,rx-latch-latency: > > > > > > + description: Rx delay to sample data with this value, > > > > > > the > > > > > > value > > > > > > + unit is clock cycle. > > > > > > > > > > Can't we use nanoseconds or microseconds as a unit here, > > > > > instead > > > > > of > > > > > clock cycles? > > > > > > > > The clock cycle will be various with MediaTek SPI NAND > > > > controller > > > > which > > > > clock frequency can support 26/52/68/81/104MHz... > > > > It`s may be easy to configure and understand with clock cycle > > > > in > > > > unit. > > > > > > > > > > Yes, but whatever clock frequency we use, the target is to always > > > wait for > > > X nanoseconds, right? > > > > > > Waiting for 5 clock cycles at 104MHz is obviously not the same as > > > waiting > > > for the same 5 clock cycles at 26MHz: in that case, expressing > > > the > > > value > > > in nanoseconds or microseconds would make that independent from > > > the > > > controller's clock frequency as the calculation from `time` to > > > `cycles` > > > would be performed inside of the driver. > > > > There have two rx related timing properties in spi-peripheral- > > props. > > The rx-sample-delay-ns have been used in Mediatek snfi driver to > > adjust > > controller sample delay. > > However another spi-rx-delay-us is in microseconds. Take 52MHz for > > example, the clock cycle will be 19.23ns which lower than 1us. This > > may > > not easy to by one clock cycle. > > > > I agree, but nothing prevents you from adding your own property for > that. > > I propose "mediatek,rx-latch-latency-ns" or "mediatek,rx-latency-ns", > so that > we can specify the delay in nanoseconds: in that case, when we > specify 19ns, > the driver will safely round that resulting in 52MHz == 19.23ns => > 19ns valid. Will be fixed in next series. Thanks Xiangsheng Hou
