[PATCH v3] firmware: arm_scmi: refactor reset domain handling

[Artem Shimko <a.shimko.dev@gmail.com>]

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.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.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

 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,
 				 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;
 
 	ret = ph->xops->xfer_get_init(ph, RESET_DOMAIN_ATTRIBUTES,
 				      sizeof(domain), sizeof(*attr), &t);
@@ -153,23 +153,39 @@ static int scmi_reset_num_domains_get(const struct scmi_protocol_handle *ph)
 	return pi->num_domains;
 }
 
+static inline struct reset_dom_info *
+scmi_reset_domain_lookup(const struct scmi_protocol_handle *ph, u32 domain)
+{
+	struct scmi_reset_info *pi = ph->get_priv(ph);
+
+	if (domain >= pi->num_domains)
+		return ERR_PTR(-EINVAL);
+
+	return pi->dom_info + domain;
+}
+
 static const char *
 scmi_reset_name_get(const struct scmi_protocol_handle *ph, u32 domain)
 {
-	struct scmi_reset_info *pi = ph->get_priv(ph);
+	struct reset_dom_info *dom_info;
 
-	struct reset_dom_info *dom = pi->dom_info + domain;
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return "unknown";
 
-	return dom->name;
+	return dom_info->name;
 }
 
 static int scmi_reset_latency_get(const struct scmi_protocol_handle *ph,
 				  u32 domain)
 {
-	struct scmi_reset_info *pi = ph->get_priv(ph);
-	struct reset_dom_info *dom = pi->dom_info + domain;
+	struct reset_dom_info *dom_info;
 
-	return dom->latency_us;
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return PTR_ERR(dom_info);
+
+	return dom_info->latency_us;
 }
 
 static int scmi_domain_reset(const struct scmi_protocol_handle *ph, u32 domain,
@@ -178,14 +194,13 @@ static int scmi_domain_reset(const struct scmi_protocol_handle *ph, u32 domain,
 	int ret;
 	struct scmi_xfer *t;
 	struct scmi_msg_reset_domain_reset *dom;
-	struct scmi_reset_info *pi = ph->get_priv(ph);
-	struct reset_dom_info *rdom;
+	struct reset_dom_info *dom_info;
 
-	if (domain >= pi->num_domains)
-		return -EINVAL;
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return PTR_ERR(dom_info);
 
-	rdom = pi->dom_info + domain;
-	if (rdom->async_reset && flags & AUTONOMOUS_RESET)
+	if (dom_info->async_reset && flags & AUTONOMOUS_RESET)
 		flags |= ASYNCHRONOUS_RESET;
 
 	ret = ph->xops->xfer_get_init(ph, RESET, sizeof(*dom), 0, &t);
@@ -238,15 +253,16 @@ static const struct scmi_reset_proto_ops reset_proto_ops = {
 static bool scmi_reset_notify_supported(const struct scmi_protocol_handle *ph,
 					u8 evt_id, u32 src_id)
 {
-	struct reset_dom_info *dom;
-	struct scmi_reset_info *pi = ph->get_priv(ph);
+	struct reset_dom_info *dom_info;
 
-	if (evt_id != SCMI_EVENT_RESET_ISSUED || src_id >= pi->num_domains)
+	if (evt_id != SCMI_EVENT_RESET_ISSUED)
 		return false;
 
-	dom = pi->dom_info + src_id;
+	dom_info = scmi_reset_domain_lookup(ph, src_id);
+	if (IS_ERR(dom_info))
+		return false;
 
-	return dom->reset_notify;
+	return dom_info->reset_notify;
 }
 
 static int scmi_reset_notify(const struct scmi_protocol_handle *ph,
@@ -363,8 +379,11 @@ static int scmi_reset_protocol_init(const struct scmi_protocol_handle *ph)
 	if (!pinfo->dom_info)
 		return -ENOMEM;
 
-	for (domain = 0; domain < pinfo->num_domains; domain++)
-		scmi_reset_domain_attributes_get(ph, pinfo, domain, version);
+	for (domain = 0; domain < pinfo->num_domains; domain++) {
+		struct reset_dom_info *dom_info = pinfo->dom_info + domain;
+
+		scmi_reset_domain_attributes_get(ph, dom_info, pinfo, domain, version);
+	}
 
 	pinfo->version = version;
 	return ph->set_priv(ph, pinfo, version);
-- 
2.43.0