linux-kernel - Re: [PATCH v2 2/3] misc: fastrpc: Add support for new DSP IOVA formatting

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Message-ID: <b3e905af-639a-4390-8fb7-50a947bf4fcf@oss.qualcomm.com>
Date: Thu, 23 Oct 2025 14:05:39 +0530
From: Kumari Pallavi <kumari.pallavi@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, kpallavi@....qualcomm.com,
        srini@...nel.org, amahesh@....qualcomm.com, arnd@...db.de,
        gregkh@...uxfoundation.org
Cc: quic_bkumar@...cinc.com, ekansh.gupta@....qualcomm.com,
        linux-kernel@...r.kernel.org, quic_chennak@...cinc.com,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        jingyi.wang@....qualcomm.com, aiqun.yu@....qualcomm.com,
        ktadakam@....qualcomm.com
Subject: Re: [PATCH v2 2/3] misc: fastrpc: Add support for new DSP IOVA
 formatting



On 10/18/2025 10:54 PM, Krzysztof Kozlowski wrote:
> On 15/10/2025 06:57, Kumari Pallavi wrote:
>>   static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>>   {
>>   	struct device *rdev = &rpdev->dev;
>> @@ -2291,6 +2319,22 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>>   	const char *domain;
>>   	bool secure_dsp;
>>   	unsigned int vmids[FASTRPC_MAX_VMIDS];
>> +	struct device_node *root;
>> +	const struct of_device_id *match;
>> +	const struct fastrpc_soc_data *soc_data = NULL;
>> +
>> +	root = of_find_node_by_path("/");
>> +	if (!root)
>> +		return -ENODEV;
>> +
>> +	match = of_match_node(qcom_soc_match_table, root);
> 
> This is really odd way of doing things. You want to check machine, not
> some node. Use proper API for that.
> 
> OTOH, I don't understand why you are checking machine in the first
> place. If your device is different, then please follow writing bindings
> - it explains exactly this case here.
> 

On the Kaanapali SoC, enabling ADSP and CDSP functionality requires new 
DSP IOVA formatting and hardware-specific configuration. Going forward, 
SoC will support the updated IOVA format.
To handle this, we referred to the implementation in
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/soc/qcom/qcom_pd_mapper.c, 
which aligns well with the requirements and serves as a suitable 
reference for our use case.
If there are alternative approaches or suggestions for handling this 
more effectively, we’re happy to discuss and consider them.

>> +	of_node_put(root);
>> +	if (!match || !match->data) {
>> +		 soc_data = &default_soc_data;
>> +		 dev_dbg(rdev, "no compatible SoC found at root node\n");
>> +	} else {
>> +		 soc_data = match->data;
>> +	}
>>   
> 
> 
> Best regards,
> Krzysztof


Thanks,
Pallavi