linux-kernel - Re: [PATCH V5 3/4] interconnect: qcom: Add EPSS L3 support on SA8775P

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Message-ID: <b2a05dfb-a820-4450-a156-8d6b4bd59be3@quicinc.com>
Date: Thu, 21 Nov 2024 23:33:04 +0530
From: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Georgi Djakov <djakov@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
CC: Odelu Kukatla <quic_okukatla@...cinc.com>,
        Mike Tipton
	<quic_mdtipton@...cinc.com>,
        Sibi Sankar <quic_sibis@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 3/4] interconnect: qcom: Add EPSS L3 support on SA8775P



On 11/21/2024 5:28 PM, Krzysztof Kozlowski wrote:
> On 21/11/2024 12:30, Raviteja Laggyshetty wrote:
>> Add Epoch Subsystem (EPSS) L3 interconnect provider on
>> SA8775P SoCs with multiple device support.
>>
> 
> 
> ...
> 
>> -DEFINE_QNODE(osm_l3_master, OSM_L3_MASTER_NODE, 16, OSM_L3_SLAVE_NODE);
>> -DEFINE_QNODE(osm_l3_slave, OSM_L3_SLAVE_NODE, 16);
>> +DEFINE_QNODE(osm_l3_master, 16, osm_l3_slave);
>> +DEFINE_QNODE(osm_l3_slave, 16);
>>  
>> -static const struct qcom_osm_l3_node * const osm_l3_nodes[] = {
>> +static struct qcom_osm_l3_node * const osm_l3_nodes[] = {
>>  	[MASTER_OSM_L3_APPS] = &osm_l3_master,
>>  	[SLAVE_OSM_L3] = &osm_l3_slave,
>>  };
>>  
>> -DEFINE_QNODE(epss_l3_master, OSM_L3_MASTER_NODE, 32, OSM_L3_SLAVE_NODE);
>> -DEFINE_QNODE(epss_l3_slave, OSM_L3_SLAVE_NODE, 32);
>> +DEFINE_QNODE(epss_l3_master, 32, epss_l3_slave);
>> +DEFINE_QNODE(epss_l3_slave, 32);
>>  
>> -static const struct qcom_osm_l3_node * const epss_l3_nodes[] = {
>> +static struct qcom_osm_l3_node * const epss_l3_nodes[] = {
> 
> 
> I think dropping const makes the code worse, not better. Commit msg does
> not explain all these changes and I could not figure out the intention
> (except modifying but that's just obvious).

EPSS L3 on SA8775P has two instances and this requires creation of two device nodes in devicetree.
As Interconnect framework requires a unique node id, each device node needs to have different compatible and data.
To overcome the need of having two different compatibles and data, driver code has been modified to acquire unique node id from IDA 
and the node name is made dynamic (nodename@...ress).
Updating node id and node name is not possible with const.
> 
> 
> 
>>  	[MASTER_EPSS_L3_APPS] = &epss_l3_master,
>>  	[SLAVE_EPSS_L3_SHARED] = &epss_l3_slave,
>>  };
>> @@ -123,6 +125,19 @@ static const struct qcom_osm_l3_desc epss_l3_l3_vote = {
>>  	.reg_perf_state = EPSS_REG_L3_VOTE,
>>  };
>>  
>> +static u16 get_node_id_by_name(const char *node_name,
>> +			       const struct qcom_osm_l3_desc *desc)
>> +{
>> +	struct qcom_osm_l3_node *const *nodes = desc->nodes;
>> +	int i;
>> +
>> +	for (i = 0; i < desc->num_nodes; i++) {
>> +		if (!strcmp(nodes[i]->name, node_name))
>> +			return nodes[i]->id;
>> +	}
>> +	return 0;
>> +}
>> +
>>  static int qcom_osm_l3_set(struct icc_node *src, struct icc_node *dst)
>>  {
>>  	struct qcom_osm_l3_icc_provider *qp;
>> @@ -164,10 +179,11 @@ static int qcom_osm_l3_probe(struct platform_device *pdev)
>>  	const struct qcom_osm_l3_desc *desc;
>>  	struct icc_onecell_data *data;
>>  	struct icc_provider *provider;
>> -	const struct qcom_osm_l3_node * const *qnodes;
>> +	struct qcom_osm_l3_node * const *qnodes;
>>  	struct icc_node *node;
>>  	size_t num_nodes;
>>  	struct clk *clk;
>> +	u64 addr;
>>  	int ret;
>>  
>>  	clk = clk_get(&pdev->dev, "xo");
>> @@ -188,6 +204,10 @@ static int qcom_osm_l3_probe(struct platform_device *pdev)
>>  	if (!qp)
>>  		return -ENOMEM;
>>  
>> +	ret = of_property_read_reg(pdev->dev.of_node, 0, &addr, NULL);
>> +	if (ret)
>> +		return ret;
>> +
>>  	qp->base = devm_platform_ioremap_resource(pdev, 0);
>>  	if (IS_ERR(qp->base))
>>  		return PTR_ERR(qp->base);
>> @@ -242,8 +262,13 @@ static int qcom_osm_l3_probe(struct platform_device *pdev)
>>  
>>  	icc_provider_init(provider);
>>  
>> +	/* Allocate unique id for qnodes */
>> +	for (i = 0; i < num_nodes; i++)
>> +		qnodes[i]->id = ida_alloc_min(&osm_l3_id, OSM_L3_NODE_ID_START, GFP_KERNEL);
>> +
>>  	for (i = 0; i < num_nodes; i++) {
>> -		size_t j;
>> +		char *node_name;
>> +		size_t j, len;
>>  
>>  		node = icc_node_create(qnodes[i]->id);
>>  		if (IS_ERR(node)) {
>> @@ -251,13 +276,29 @@ static int qcom_osm_l3_probe(struct platform_device *pdev)
>>  			goto err;
>>  		}
>>  
>> -		node->name = qnodes[i]->name;
>> +		/* len = strlen(node->name) + @ + 8 (base-address) + NULL */
>> +		len = strlen(qnodes[i]->name) + OSM_NODE_NAME_SUFFIX_SIZE;
>> +		node_name = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
>> +		if (!node_name) {
>> +			ret = -ENOMEM;
>> +			goto err;
>> +		}
>> +
>> +		snprintf(node_name, len, "%s@...llx", qnodes[i]->name, addr);
>> +		node->name = node_name;
> 
> 
> Why the node name becomes dynamic?
> 
> Best regards,
> Krzysztof