On Wed, Mar 27, 2019 at 11:33 AM Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote: > > Hi Daniel, > > Am Mittwoch, den 27.03.2019, 10:51 +0200 schrieb Daniel Baluta: > [...] > > > > > or > > > "fsl,imx8qxp-edma", "fsl,imx8qm-edma"? > > > > One thing that it is not clear for me is why there are places > > where we use two compatible strings? > > > > I understand the situation where are two distinct drivers, but is there > > any other reason to add multiple compatible strings for a node in dts? > > We use 2 compatible string where there should not be any differences > between the IP blocks of this SoC and a version the driver already > supports. > > So if the eDMA driver already supports the software interface for > "fsl,imx8qm-edma" and the IP block is compatible with this, we add this > to the DT, so the we don't need any driver changes just to support a > new SoC. But as you can never be sure if there are subtle differences > in the IP block and/or SOC integration when adding the DT support, we > also add a more specific compatible to the DT. If it turns out that > there are software visible differences, we only need to adapt the > driver to check for the more specific compatible to trigger the changed > behavior, allowing to keep the DT stable. Excellent explanation Lucas! For the moment upstream eDMA driver doesn't have support for any i.MX8 so I think using "fsl,imx8qxp-edma" should be acceptable. Thanks, Daniel.
