linux-kernel - Re: [PATCH v5 3/3] mtd: core: introduce of support for dynamic partitions

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Message-ID: <d98dd483-70b9-4bd1-0463-9e3343576955@gmail.com>
Date:   Mon, 17 Oct 2022 23:52:34 +0200
From:   Rafał Miłecki <zajec5@...il.com>
To:     "han.xu" <han.xu@....com>, Ansuel Smith <ansuelsmth@...il.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        �ecki <rafal@...ecki.pl>,
        Manivannan Sadhasivam <mani@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] mtd: core: introduce of support for dynamic
 partitions

On 17.10.2022 21:59, han.xu wrote:
> On 22/06/06 05:14PM, Ansuel Smith wrote:
>> We have many parser that register mtd partitions at runtime. One example
>> is the cmdlinepart or the smem-part parser where the compatible is defined
>> in the dts and the partitions gets detected and registered by the
>> parser. This is problematic for the NVMEM subsystem that requires an OF node
>> to detect NVMEM cells.
>>
>> To fix this problem, introduce an additional logic that will try to
>> assign an OF node to the MTD if declared.
>>
>> On MTD addition, it will be checked if the MTD has an OF node and if
>> not declared will check if a partition with the same label is
>> declared in DTS. If an exact match is found, the partition dynamically
>> allocated by the parser will have a connected OF node.
>>
>> The NVMEM subsystem will detect the OF node and register any NVMEM cells
>> declared statically in the DTS.
>>
>> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
>> ---
>>   drivers/mtd/mtdcore.c | 49 +++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 49 insertions(+)
>>
>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
>> index 7731796024e0..807194efb580 100644
>> --- a/drivers/mtd/mtdcore.c
>> +++ b/drivers/mtd/mtdcore.c
>> @@ -546,6 +546,54 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
>>   	return 0;
>>   }
>>   
>> +static void mtd_check_of_node(struct mtd_info *mtd)
>> +{
>> +	struct device_node *partitions, *parent_dn, *mtd_dn = NULL;
>> +	struct mtd_info *parent;
>> +	const char *mtd_name;
>> +	bool found = false;
>> +	int plen;
>> +
>> +	/* Check if MTD already has a device node */
>> +	if (dev_of_node(&mtd->dev))
>> +		return;
>> +
>> +	/* Check if a partitions node exist */
>> +	parent = mtd->parent;
>> +	parent_dn = dev_of_node(&parent->dev);
>> +	if (!parent_dn)
>> +		return;
>> +
>> +	partitions = of_get_child_by_name(parent_dn, "partitions");
>> +	if (!partitions)
>> +		goto exit_parent;
>> +
>> +	/* Search if a partition is defined with the same name */
>> +	for_each_child_of_node(partitions, mtd_dn) {
>> +		/* Skip partition with no label */
>> +		mtd_name = of_get_property(mtd_dn, "label", &plen);
>> +		if (!mtd_name)
>> +			continue;
>> +
>> +		if (!strncmp(mtd->name, mtd_name, plen)) {
>> +			found = true;
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (!found)
>> +		goto exit_partitions;
>> +
>> +	/* Set of_node only for nvmem */
>> +	if (of_device_is_compatible(mtd_dn, "nvmem-cells"))
>> +		mtd_set_of_node(mtd, mtd_dn);
>> +
>> +exit_partitions:
>> +	of_node_put(partitions);
>> +exit_parent:
>> +	of_node_put(parent_dn);
>> +}
>> +
>>   /**
>>    *	add_mtd_device - register an MTD device
>>    *	@mtd: pointer to new MTD device info structure
>> @@ -651,6 +699,7 @@ int add_mtd_device(struct mtd_info *mtd)
>>   	mtd->dev.devt = MTD_DEVT(i);
>>   	dev_set_name(&mtd->dev, "mtd%d", i);
>>   	dev_set_drvdata(&mtd->dev, mtd);
>> +	mtd_check_of_node(mtd);
>>   	of_node_get(mtd_get_of_node(mtd));
>>   	error = device_register(&mtd->dev);
>>   	if (error)
> 
> NXP GPMI NAND controller with 6 cmdline partitions meets refcount underflow
> with this patch. The of_node_put(parent_dn) doesn't work with cmdline parser and
> causes the issue.

Can you try:

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 18aa54460d36..0b4ca0aa4132 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -562,7 +562,7 @@ static void mtd_check_of_node(struct mtd_info *mtd)
  	if (!mtd_is_partition(mtd))
  		return;
  	parent = mtd->parent;
-	parent_dn = dev_of_node(&parent->dev);
+	parent_dn = of_node_get(dev_of_node(&parent->dev));
  	if (!parent_dn)
  		return;