linux-kernel - Re: [PATCH v3 1/6] memory: omap-gpmc: Store handle to GPMC dev

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Date:	Thu, 10 Mar 2016 09:24:44 -0600
From:	"Franklin S Cooper Jr." <fcooper@...com>
To:	Roger Quadros <rogerq@...com>
CC:	<nsekhar@...com>, <dwmw2@...radead.org>,
	<computersforpeace@...il.com>, <tony@...mide.com>,
	<devicetree@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/6] memory: omap-gpmc: Store handle to GPMC dev



On 03/10/2016 09:22 AM, Roger Quadros wrote:
> Franklin,
>
> On 10/03/16 15:40, Franklin S Cooper Jr. wrote:
>>
>> On 03/10/2016 06:40 AM, Roger Quadros wrote:
>>> Franklin,
>>>
>>> On 10/03/16 06:07, Franklin S Cooper Jr wrote:
>>>> The dma channel information is located within the GPMC node. The NAND
>>>> driver requires a handle to the GPMC's dev to properly parse the DMA
>>>> properties. Therefore, store a handle to the dev so it can be referenced
>>>> within the NAND driver.
>>>>
>>>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
>>>> ---
>>>>  drivers/memory/omap-gpmc.c                   | 1 +
>>>>  include/linux/platform_data/mtd-nand-omap2.h | 2 ++
>>>>  2 files changed, 3 insertions(+)
>>>>
>>>> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
>>>> index 6515dfc..2932d13 100644
>>>> --- a/drivers/memory/omap-gpmc.c
>>>> +++ b/drivers/memory/omap-gpmc.c
>>>> @@ -1796,6 +1796,7 @@ static int gpmc_probe_nand_child(struct platform_device *pdev,
>>>>  
>>>>  	gpmc_nand_data->cs = val;
>>>>  	gpmc_nand_data->of_node = child;
>>>> +	gpmc_nand_data->gpmc_dev = &pdev->dev;
>>>>  
>>>>  	/* Detect availability of ELM module */
>>>>  	gpmc_nand_data->elm_of_node = of_parse_phandle(child, "ti,elm-id", 0);
>>>> diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
>>>> index 090bbab..534b984 100644
>>>> --- a/include/linux/platform_data/mtd-nand-omap2.h
>>>> +++ b/include/linux/platform_data/mtd-nand-omap2.h
>>>> @@ -80,5 +80,7 @@ struct omap_nand_platform_data {
>>>>  	/* for passing the partitions */
>>>>  	struct device_node	*of_node;
>>>>  	struct device_node	*elm_of_node;
>>>> +
>>>> +	struct device		*gpmc_dev;
>>>>  };
>>>>  #endif
>>>>
>>> Why do you need this? Can't we just use dev->parent in the omap2-nand driver?
>> The omap2-nand platform_device is created by
>> platform_device_alloc. The created platform_device dev
>> parent isn't by default set to the GPMC dev. I didn't think
>> this was the right approach to manually set the parent
>> property. However, taking a look at other usages of
>> platform_device_alloc it seems this is actually pretty
>> common. If your ok with this then I can go that route.
> After my DT cleanup we no longer use platform_dev_alloc for DT cases.
> As Nand node is child of GPMC node, omap2 nand's parent is guaranteed to be the
> GPMC device.
>
> But for legacy boot we still use gpmc_nand_init() which calls platform_device_add()
> without setting pdev->parent and so it will set the parent to platform bus.
>
> Maybe we could patch gpmc_nand_init() to set NAND's parent to GPMC device?

Yup that was my plan. I'll send a rev 4 with this change and
also your comments on PATCH 2.
>
> cheers,
> -roger