Re: [PATCH v4 6/7] arm/mpu: Provide a constructor for pr_t type

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

>> +    switch ( attr_idx )
>> +    {
>> +    case MT_NORMAL_NC:
>> +        /*
>> +         * ARM ARM: Overlaying the shareability attribute (DDI
>> +         * 0406C.b B3-1376 to 1377)
> It's a bit odd to provide here the manual for Armv7.
> Also, our general advice is to use the latest revision.

I’m thinking about restructuring in this way:

    switch ( attr_idx )
    {
    /*
     * ARM ARM: Shareable, Inner Shareable, and Outer Shareable Normal memory
     * (DDI 0487L.a B2.10.1.1.1 Note section):
     *
     * Because all data accesses to Non-cacheable locations are data coherent
     * to all observers, Non-cacheable locations are always treated as Outer
     * Shareable
     *
     * ARM ARM: Device memory (DDI 0487L.a B2.10.2)
     *
     * All of these memory types have the following properties:
     * [...]
     *  - Data accesses to memory locations are coherent for all observers in
     *    the system, and correspondingly are treated as being Outer Shareable
     */
    case MT_NORMAL_NC:
        /* Fall through */
    case MT_DEVICE_nGnRnE:
        /* Fall through */
    case MT_DEVICE_nGnRE:
        prbar.reg.sh = LPAE_SH_OUTER;
        break;
    default:
        /* Xen mappings are SMP coherent */
        prbar.reg.sh = LPAE_SH_INNER;
        break;
    }

what do you think? It will have the fall through comment and will also explain 
the LPAE_SH_OUTER value set
for both normal memory nc and device memory.

Please let me know.

Cheers,
Luca