linux-kernel - Re: [PATCH v4] firmware: arm_scmi: refactor reset domain handling

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Message-ID: <CAOPX747pTsnTzKnaai-ytnmcf6reraTTSk+mssvHri4GMhCsOA@mail.gmail.com>
Date: Fri, 5 Dec 2025 13:36:23 +0300
From: Artem Shimko <a.shimko.dev@...il.com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: cristian.marussi@....com, arm-scmi@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] firmware: arm_scmi: refactor reset domain handling

On Thu, Dec 4, 2025 at 7:26 PM Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Sun, Nov 23, 2025 at 07:35:57PM +0300, Artem Shimko wrote:
> > Improve the SCMI reset protocol implementation by centralizing domain
> > validation and enhancing error handling.
> >
> > Add scmi_reset_domain_lookup() helper function to validate
> > domain ids and return appropriate error codes. Refactor all
> > domain-specific functions to use this helper, ensuring consistent
> > error handling throughout the reset protocol.
> >
> > Suggested-by: Cristian Marussi <cristian.marussi@....com>
> > Signed-off-by: Artem Shimko <a.shimko.dev@...il.com>
> > ---
> >
> > Hi Cristian,
> >
> > Thank you for suggesting! If it works for you I'll try to improve the others protocols.
> >
> > It was tested on my board in QEMU and on real hardware.
> > The functionality didn't break, and peripherals that are reseted via SCMI work correctly.
> >
> > As an example, I can provide DMA test results (as one of the processor units dependent on SCMI reset).
> >
> > [    2.559040] dw_axi_dmac_platform 1000nda0.nda_dma_0: DesignWare AXI DMA Controller, nda channels
> > [    2.569265] dw_axi_dmac_platform 1000nda0.nda_dma_1: DesignWare AXI DMA Controller, nda channels
> > [    2.580601] dw_axi_dmac_platform 1000nda0.nda_dma_2: DesignWare AXI DMA Controller, nda channels
> >
> > # echo 2000 > /sys/module/dmatest/parameters/timeout
> > # echo 1000 > /sys/module/dmatest/parameters/iterations
> > # echo dma0chan0 > /sys/module/dmatest/parameters/channel
> > [   95.917504] dmatest: Added 1 threads using dma0chan0
> > # echo 1 > /sys/module/dmatest/parameters/run
> > [  101.931372] dmatest: Started 1 threads using dma0chan0
> > [  102.731009] dmatest: dma0chan0-copy0: summary 1000 tests, 0 failures 2508.42 iops 19706 KB/s (0)
> >
> > And vice versa:
> >
> > 1. Confirmed that the DMA module is non-functional without a proper reset via SCMI.
> > Disabling the reset logic causes a system crash on first access to its registers.
> >
> > 2. Requesting a non-existent reset domain:
> >
> > [    2.463400] dw_axi_dmac_platform 1000nda0.nda_dma_0: error -EINVAL: Failed to deassert resets
> > [    2.472091] dw_axi_dmac_platform 1000nda0.nda_dma_0: probe with driver dw_axi_dmac_platform failed with error -22
> > [    2.482911] dw_axi_dmac_platform 1000nda0.nda_dma_1: error -EINVAL: Failed to deassert resets
> > [    2.491553] dw_axi_dmac_platform 1000nda0.nda_dma_1: probe with driver dw_axi_dmac_platform failed with error -22
> > [    2.502256] dw_axi_dmac_platform 1000nda0.nda_dma_2: error -EINVAL: Failed to deassert resets
> > [    2.510735] dw_axi_dmac_platform 1000nda0.nda_dma_2: probe with driver dw_axi_dmac_platform failed with error -22
> >
> > --
> > Regards,
> > Artem
> >
> > ---
> > ChangeLog:
> >   v4: Add Suggested-by tag
> >
> >  drivers/firmware/arm_scmi/reset.c | 59 ++++++++++++++++++++-----------
> >  1 file changed, 39 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/firmware/arm_scmi/reset.c b/drivers/firmware/arm_scmi/reset.c
> > index 0aa82b96f41b..9854a3016d13 100644
> > --- a/drivers/firmware/arm_scmi/reset.c
> > +++ b/drivers/firmware/arm_scmi/reset.c
> > @@ -100,6 +100,7 @@ static int scmi_reset_attributes_get(const struct scmi_protocol_handle *ph,
> >
> >  static int
> >  scmi_reset_domain_attributes_get(const struct scmi_protocol_handle *ph,
> > +                              struct reset_dom_info *dom_info,
>
> Instead of changing this, ...
>
> >                                struct scmi_reset_info *pinfo,
> >                                u32 domain, u32 version)
> >  {
> > @@ -107,7 +108,6 @@ scmi_reset_domain_attributes_get(const struct scmi_protocol_handle *ph,
> >       u32 attributes;
> >       struct scmi_xfer *t;
> >       struct scmi_msg_resp_reset_domain_attributes *attr;
> > -     struct reset_dom_info *dom_info = pinfo->dom_info + domain;
> >
>
> ... You can just follow the pattern you have done everywhere else in this
> change like:
>
> struct reset_dom_info *dom_info;
>
> dom_info = scmi_reset_domain_lookup(ph, domain);
> if (IS_ERR(dom_info))
>         return PTR_ERR(dom_info);
>
> Any particular reason for not doing that ?

Hi Sudeep,

Based on perf.c, I added this pattern only to functions that can be
called externally with an invalid domain value.
Therefore, I decided it would be better to change the signature of
scmi_reset_domain_attributes_get (similar to
scmi_perf_domain_attributes_get from pref.c)
to ensure consistency across drivers when working with domain numbers.

If you believe this pattern should be used in
scmi_reset_domain_attributes_get, I'll send you the next version of
the patch.

Thank you very much for reviewing my changes =)

Regards,
Artem