On Wed, Jan 25, 2023 at 10:42:13AM +0000, Robin Murphy wrote: > On 2023-01-25 08:54, Geert Uytterhoeven wrote: > > Hi Shimoda-san, > > > > On Wed, Jan 25, 2023 at 1:49 AM Yoshihiro Shimoda > > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: > > > > From: Geert Uytterhoeven, Sent: Tuesday, January 24, 2023 11:35 PM > > > > On Mon, Jan 23, 2023 at 2:35 AM Yoshihiro Shimoda > > > > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: > > > > > Since R-Car Gen4 doens't have the main IPMMU IMSSTR register, but > > > > > each cache IPMMU has own module id. So, update descriptions of > > > > > renesas,ipmmu-main property for R-Car Gen4. > > > > > > > > > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> > > > > > > > --- > > > > > The old R-Car S4-8 datasheet had described IPMMU IMSSTR register, but > > > > > the latest datasheet undocumented the register. So, update the propeties > > > > > description. Note that the second argument is not used on the driver. > > > > > > > > DT describes hardware, not software policy. > > > > > > I think so. > > > > > > > > So no behavior change. > > > > > > > > So where do we get the module id numbers to use, if they are no longer > > > > documented in the Hardware Manual? > > > > > > If so, we cannot get the module id numbers. So, should we use other > > > information which is completely fixed instead? I have some ideas: > > > 1) Just 0 (or other fixed value) if the IMSSTR register doesn't exist. > > > 2) Sequential numbers from register base offset. > > > In R-Car S4: ipmmu_rt0 is the first node from register base offset, > > > and ipmmu_rt1 is the second one. > > > So, ipmmu_rt0 is 0, ipmmu_rt1 is 1, ipmmu_ds0 is 2 and ipmmu_hc is 3. > > > 3) Using base address upper 16-bits. > > > In R-Car S4: ipmmu_rt0 is 0xee480000. So, the value is 0xee48. > > > > > > Perhaps, the option 1) is reasonable, I think. But, what do you think? > > > > I would not make up numbers, as that would cause confusion with SoCs > > where the numbers do match the hardware. > > As the driver doesn't use the module id number (it already loops > > over all domains, instead of checking IMSSTR, probably because of > > historical (R-Car Gen2) reasons?), what about dropping it from the > > property? I.e. add "minItems: 1", possibly only when compatible with > > renesas,rcar-gen4-ipmmu-vmsa? > > Right, if there really is no meaningful ID for this model then its binding > should not require one. I agree, however that makes parsing the property a pain (for both the schema and driver). This property is a matrix. The number of entries is already variable. If both dimensions are variable, we have to then look at the compatible to know how to parse it. I would go with option 1. A 4th option is a new property. Rob
