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

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Message-ID: <20251204-slick-granite-chameleon-58ebc2@sudeepholla>
Date: Thu, 4 Dec 2025 16:16:21 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Artem Shimko <a.shimko.dev@...il.com>
Cc: cristian.marussi@....com, arm-scmi@...r.kernel.org,
	Artem Shimko <a.shimko.dev@...il.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] firmware: arm_scmi: refactor reset domain handling

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 ?

-- 
Regards,
Sudeep