linux-kernel - Re: [PATCH v3 3/4] memory: omap-gpmc: Use a compatible match table when checking for NAND controller

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Date:   Mon, 20 Dec 2021 12:53:44 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        tony@...mide.com
Cc:     robh@...nel.org, kishon@...com, nm@...com, vigneshr@...com,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 3/4] memory: omap-gpmc: Use a compatible match table
 when checking for NAND controller



On 17/12/2021 17:21, Krzysztof Kozlowski wrote:
> On 17/12/2021 11:29, Roger Quadros wrote:
>> As more compatibles can be added to the GPMC NAND controller driver
>> use a compatible match table.
>>
>> Signed-off-by: Roger Quadros <rogerq@...nel.org>
>> ---
>>  drivers/memory/omap-gpmc.c                   | 8 +++++++-
>>  drivers/mtd/nand/raw/omap2.c                 | 2 +-
>>  include/linux/platform_data/mtd-nand-omap2.h | 5 +++++
>>  3 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
>> index 624153048182..814ddb45c13d 100644
>> --- a/drivers/memory/omap-gpmc.c
>> +++ b/drivers/memory/omap-gpmc.c
>> @@ -2091,6 +2091,7 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
>>  	u32 val;
>>  	struct gpio_desc *waitpin_desc = NULL;
>>  	struct gpmc_device *gpmc = platform_get_drvdata(pdev);
>> +	bool is_nand = false;
>>  
>>  	if (of_property_read_u32(child, "reg", &cs) < 0) {
>>  		dev_err(&pdev->dev, "%pOF has no 'reg' property\n",
>> @@ -2183,7 +2184,12 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
>>  		}
>>  	}
>>  
>> -	if (of_device_is_compatible(child, "ti,omap2-nand")) {
>> +#if defined(CONFIG_MTD_NAND_OMAP2)
> 
> if (IS_ENABLED()) is preferred. If needed, you could make omap_nand_ids
> symbol visible always (so without ifdef around it), because extern
> structure should not have impact when not defined (if I recall
> correctly...).
> 
>> +	if (of_match_node(omap_nand_ids, child))
>> +		is_nand = true;
>> +#endif
>> +
>> +	if (is_nand) {
>>  		/* NAND specific setup */
>>  		val = 8;
>>  		of_property_read_u32(child, "nand-bus-width", &val);
>> diff --git a/drivers/mtd/nand/raw/omap2.c b/drivers/mtd/nand/raw/omap2.c
>> index b26d4947af02..fff834ee726f 100644
>> --- a/drivers/mtd/nand/raw/omap2.c
>> +++ b/drivers/mtd/nand/raw/omap2.c
>> @@ -2352,7 +2352,7 @@ static int omap_nand_remove(struct platform_device *pdev)
>>  	return ret;
>>  }
>>  
>> -static const struct of_device_id omap_nand_ids[] = {
>> +const struct of_device_id omap_nand_ids[] = {
>>  	{ .compatible = "ti,omap2-nand", },
>>  	{},
>>  };
> 
> I think OMAP2 NAND driver can be a module, so this should have
> EXPORT_SYMBOL.

To make it work in all combinations (e.g. omap_gpmc built in and
nand/raw/omap2.c as module) I had to define omap_nand_ids table as static
in the linux/platform_data/mtd-nand-omap2.h header.

EXPORT_SYMBOL will of course be not required there. ;)

> 
>> diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
>> index de6ada739121..e1bb90a8db03 100644
>> --- a/include/linux/platform_data/mtd-nand-omap2.h
>> +++ b/include/linux/platform_data/mtd-nand-omap2.h
>> @@ -61,4 +61,9 @@ struct gpmc_nand_regs {
>>  	void __iomem	*gpmc_bch_result5[GPMC_BCH_NUM_REMAINDER];
>>  	void __iomem	*gpmc_bch_result6[GPMC_BCH_NUM_REMAINDER];
>>  };
>> +
>> +#if defined(CONFIG_MTD_NAND_OMAP2)
>> +extern const struct of_device_id omap_nand_ids[];
>> +#endif
>> +
>>  #endif
>>
> 
> 
> Best regards,
> Krzysztof
> 

cheers,
-roger