Re: [PATCH 0/2] Resolve MPM register space situation

Shawn Guo
2023-03-29T03:34:38Z

On Tue, Mar 28, 2023 at 12:02:51PM +0200, Konrad Dybcio wrote:
> The MPM (and some other things, irrelevant to this patchset) resides
> (as far as the ARM cores are concerned, anyway) in a MMIO-mapped region
> that's a portion of the RPM (low-power management core)'s RAM, known
> as the RPM Message RAM. Representing this relation in the Device Tree
> creates some challenges, as one would either have to treat a memory
> region as a bus, map nodes in a way such that their reg-s would be
> overlapping, or supply the nodes with a slice of that region.
>
> This series implements the third option, by adding a qcom,rpm-msg-ram
> property, which has been used for some drivers poking into this region
> before. Bindings ABI compatibility is preserved through keeping the
> "normal" (a.k.a read the reg property and map that region) way of
> passing the register space.

I have to admit that I wasn't aware of it, this message RAM is also
accessed by cores like modem, ADSP etc. I agree in principle this is
a good change!

Shawn

>
> Example representation with this patchset:
>
> / {
> [...]
>
> mpm: interrupt-controller {
> compatible = "qcom,mpm";
> qcom,rpm-msg-ram = <&apss_mpm>;
> [...]
> };
>
> [...]
>
> soc: soc@0 {
> [...]
>
> rpm_msg_ram: sram@45f0000 {
> compatible = "qcom,rpm-msg-ram", "mmio-sram";
> reg = <0 0x045f0000 0 0x7000>;
> #address-cells = <1>;
> #size-cells = <1>;
> ranges = <0 0x0 0x045f0000 0x7000>;
>
> apss_mpm: sram@1b8 {
> reg = <0x1b8 0x48>;
> };
> };
> };
> };
>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
> ---
> Konrad Dybcio (2):
> dt-bindings: interrupt-controller: mpm: Allow passing reg through phandle
> irqchip: irq-qcom-mpm: Support passing a slice of SRAM as reg space
>
> .../bindings/interrupt-controller/qcom,mpm.yaml | 6 ++++-
> drivers/irqchip/irq-qcom-mpm.c | 30 ++++++++++++++++++----
> 2 files changed, 30 insertions(+), 6 deletions(-)
> ---
> base-commit: a6faf7ea9fcb7267d06116d4188947f26e00e57e
> change-id: 20230328-topic-msgram_mpm-c688be3bc294
>
> Best regards,
> --
> Konrad Dybcio <konrad.dybcio@linaro.org>
>