Re: [PATCH v4 3/3] arm/mpu: Enable read/write to protection regions for arm32

[Hari Limaye <hari.limaye@xxxxxxx>]

Hi Ayan,

> +/*
> + * Armv8-R supports direct access and indirect access to the MPU regions 
> through
> + * registers:
> + *  - indirect access involves changing the MPU region selector, issuing an 
> isb
> + *    barrier and accessing the selected region through specific registers
> + *  - direct access involves accessing specific registers that point to
> + *    specific MPU regions, without changing the selector, avoiding the use 
> of
> + *    a barrier.
> + * For Arm32 the HPR{B,L}AR<n> (for n=0..31) are used for direct access to 
> the
> + * first 32 MPU regions.
> + * For MPU region numbered 32..254, one need to set the region number in 
> HPRSELR,
> + * followed by configuring HPR{B,L}AR.
> + */
> +static void prepare_selector(uint8_t *sel)

NIT: s/one need/one needs/
NIT: s/MPU region numbered/MPU regions numbered/

Also - it's not clear to me what is meant by "followed by configuring 
HPR{B,L}AR";
if I understand correctly, once we have set the region number in HPRSELR
and issued an isb we can simply read/write HPR{B,L}AR as indicated in
the bullet point above?

> On Tue, Jun 17, 2025 at 12:12:51PM +0000, Ayan Kumar Halder wrote:
> Define prepare_selector(), read_protection_region() and
> write_protection_region() for arm32. Also, define
> GENERATE_{READ/WRITE}_PR_REG_OTHERS to access MPU regions from 32 to 254.
> 
> Enable pr_{get/set}_{base/limit}(), region_is_valid() for arm32.
> Enable pr_of_addr() for arm32.
> 
> The maximum number of regions supported is 255 (which corresponds to the
> maximum value in HMPUIR).
> 
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> ---

Apart from the above, all LGTM! I've tested compilation for both 64-bit
and 32-bit and all is building successfully.

Reviewed-by: Hari Limaye <hari.limaye@xxxxxxx>
Tested-by: Hari Limaye <hari.limaye@xxxxxxx>

Cheers,
Hari