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Message-ID: <b90d3b99-a4d2-86f5-be9a-803b33d787b6@arm.com>
Date:   Mon, 27 Mar 2023 15:27:39 +0100
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Subject: Re: [PATCH] perf/arm-cmn: Fix and refactor device mapping resource
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To:     Will Deacon <will@kernel.org>,
        Jing Zhang <renyu.zj@linux.alibaba.com>,
        ilkka@os.amperecomputing.com
Cc:     Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Shuai Xue <xueshuai@linux.alibaba.com>,
        Zhuo Song <zhuo.song@linux.alibaba.com>
References: <1676535470-120560-1-git-send-email-renyu.zj@linux.alibaba.com>
 <20230327140536.GB31752@willie-the-truck>
From:   Robin Murphy <robin.murphy@arm.com>
In-Reply-To: <20230327140536.GB31752@willie-the-truck>
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On 2023-03-27 15:05, Will Deacon wrote:
> [+Robin and Ilkka, as they contribute most to this driver]
> 
> On Thu, Feb 16, 2023 at 04:17:50PM +0800, Jing Zhang wrote:
>> The devm_platform_ioremap_resource() won't let the platform device
>> claim resource when the ACPI companion device has already claimed it.
>> If CMN-ANY except CMN600 is ACPI companion device, it will return
>> -EBUSY in devm_platform_ioremap_resource(), and the driver cannot be
>> successfully installed.
>>
>> So let ACPI companion device call arm_cmn_acpi_probe and not claim
>> resource again. In addition, the arm_cmn_acpi_probe() and
>> arm_cmn_of_probe() functions are refactored to make them compatible
>> with both CMN600 and CMN-ANY.

No, the whole point of CMN-600 probing being a special case is that the 
ACPI and DT bindings for CMN-600 are special cases. In ACPI, only 
ARMHC600 has the two nested memory resources; all the other models 
should only have one memory resource because one is all that is 
meaningful. See table 16 the document[1] in where the description of 
ROOTNODEBASE says "This field is specific to the CMN-600 device object."

Similarly in DT, "arm,root-node" is only required for "arm,cmn-600" - it 
didn't seem worth overcomplicating the schema to actively disallow it 
for other models, but that is supposed to be implied by its description 
as "not relevant for newer CMN/CI products".

If you're hitting this because you've written your ACPI DSDT 
incorrectly, it's a sign that you should fix your DSDT.

Thanks,
Robin.

[1] https://developer.arm.com/documentation/den0093/latest/

>> Fixes: 61ec1d875812 ("perf/arm-cmn: Demarcate CMN-600 specifics")
>> Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com>
>> ---
>>   drivers/perf/arm-cmn.c | 57 ++++++++++++++++++++++++++++++++------------------
>>   1 file changed, 37 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
>> index 1deb61b..beb3b37 100644
>> --- a/drivers/perf/arm-cmn.c
>> +++ b/drivers/perf/arm-cmn.c
>> @@ -2206,7 +2206,7 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
>>   	return 0;
>>   }
>>   
>> -static int arm_cmn600_acpi_probe(struct platform_device *pdev, struct arm_cmn *cmn)
>> +static int arm_cmn_acpi_probe(struct platform_device *pdev, struct arm_cmn *cmn)
>>   {
>>   	struct resource *cfg, *root;
>>   
>> @@ -2214,12 +2214,21 @@ static int arm_cmn600_acpi_probe(struct platform_device *pdev, struct arm_cmn *c
>>   	if (!cfg)
>>   		return -EINVAL;
>>   
>> -	root = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>> -	if (!root)
>> -		return -EINVAL;
>> +	/* If ACPI defines more than one resource, such as cmn-600, then there may be
>> +	 * a deviation between ROOTNODEBASE and PERIPHBASE, and ROOTNODEBASE can
>> +	 * be obtained from the second resource. Otherwise, it can be considered that
>> +	 * ROOT NODE BASE is PERIPHBASE. This is compatible with cmn-600 and cmn-any.
>> +	 */
>> +	if (pdev->num_resources > 1) {
>> +		root = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>> +		if (!root)
>> +			return -EINVAL;
>>   
>> -	if (!resource_contains(cfg, root))
>> -		swap(cfg, root);
>> +		if (!resource_contains(cfg, root))
>> +			swap(cfg, root);
>> +	} else {
>> +		root = cfg;
>> +	}
>>   	/*
>>   	 * Note that devm_ioremap_resource() is dumb and won't let the platform
>>   	 * device claim cfg when the ACPI companion device has already claimed
>> @@ -2227,17 +2236,30 @@ static int arm_cmn600_acpi_probe(struct platform_device *pdev, struct arm_cmn *c
>>   	 * appropriate name, we don't really need to do it again here anyway.
>>   	 */
>>   	cmn->base = devm_ioremap(cmn->dev, cfg->start, resource_size(cfg));
>> -	if (!cmn->base)
>> -		return -ENOMEM;
>> +	if (IS_ERR(cmn->base))
>> +		return PTR_ERR(cmn->base);
>>   
>>   	return root->start - cfg->start;
>>   }
>>   
>> -static int arm_cmn600_of_probe(struct device_node *np)
>> +static int arm_cmn_of_probe(struct platform_device *pdev, struct arm_cmn *cmn)
>>   {
>>   	u32 rootnode;
>> +	int ret;
>> +
>> +	cmn->base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(cmn->base))
>> +		return PTR_ERR(cmn->base);
>>   
>> -	return of_property_read_u32(np, "arm,root-node", &rootnode) ?: rootnode;
>> +	/* If of_property_read_u32() return EINVAL, it means that device tree has
>> +	 * not define root-node, and root-node will return 0, which is compatible
>> +	 * with cmn-600 and cmn-any.
>> +	 */
>> +	ret = of_property_read_u32(pdev->dev.of_node, "arm,root-node", &rootnode);
>> +	if (ret == -EINVAL)
>> +		return 0;
>> +
>> +	return rootnode;
>>   }
>>   
>>   static int arm_cmn_probe(struct platform_device *pdev)
>> @@ -2255,16 +2277,11 @@ static int arm_cmn_probe(struct platform_device *pdev)
>>   	cmn->model = (unsigned long)device_get_match_data(cmn->dev);
>>   	platform_set_drvdata(pdev, cmn);
>>   
>> -	if (cmn->model == CMN600 && has_acpi_companion(cmn->dev)) {
>> -		rootnode = arm_cmn600_acpi_probe(pdev, cmn);
>> -	} else {
>> -		rootnode = 0;
>> -		cmn->base = devm_platform_ioremap_resource(pdev, 0);
>> -		if (IS_ERR(cmn->base))
>> -			return PTR_ERR(cmn->base);
>> -		if (cmn->model == CMN600)
>> -			rootnode = arm_cmn600_of_probe(pdev->dev.of_node);
>> -	}
>> +	if (has_acpi_companion(cmn->dev))
>> +		rootnode = arm_cmn_acpi_probe(pdev, cmn);
>> +	else
>> +		rootnode = arm_cmn_of_probe(pdev, cmn);
>> +
>>   	if (rootnode < 0)
>>   		return rootnode;
>>   
>> -- 
>> 1.8.3.1
>>