linux-kernel - Re: [PATCH 3/8] drm/mediatek: mt2701: switch to mfd probing.

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Date:   Thu, 23 Nov 2017 09:30:17 +0100
From:   Matthias Brugger <mbrugger@...e.com>
To:     CK Hu <ck.hu@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     ulrich.hecht+renesas@...il.com, laurent.pinchart@...asonboard.com,
        p.zabel@...gutronix.de, airlied@...ux.ie, robh+dt@...nel.org,
        mark.rutland@....com, mturquette@...libre.com,
        sboyd@...eaurora.org, lee.jones@...aro.org, davem@...emloft.net,
        gregkh@...uxfoundation.org, mchehab@...nel.org,
        rdunlap@...radead.org, pi-cheng.chen@...aro.org,
        sean.wang@...iatek.com, linux-clk@...r.kernel.org,
        linux@...linux.org.uk, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 3/8] drm/mediatek: mt2701: switch to mfd probing.



On 11/23/2017 06:48 AM, CK Hu wrote:
> Hi, Matthias:
> 
> On Tue, 2017-11-14 at 22:41 +0100, Matthias Brugger wrote:
>> With the mtk-mmsys MFD device in place, we switch the probing for
>> mt2701 from device-tree to mfd.
>>
>> Signed-off-by: Matthias Brugger <mbrugger@...e.com>
>> ---
>>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 32 +++++++++++++++++++++++++-------
>>  1 file changed, 25 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>> index dd249cf5121e..5a263aa3ab6e 100644
>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>> @@ -21,6 +21,7 @@
>>  #include <drm/drm_of.h>
>>  #include <linux/component.h>
>>  #include <linux/iommu.h>
>> +#include <linux/mfd/mmsys.h>
>>  #include <linux/mfd/syscon.h>
>>  #include <linux/of_address.h>
>>  #include <linux/of_platform.h>
>> @@ -392,9 +393,10 @@ static const struct of_device_id mtk_ddp_comp_dt_ids[] = {
>>  
>>  static int mtk_drm_probe(struct platform_device *pdev)
>>  {
>> +	struct mmsys_dev *mmsys_private;
>>  	struct device *dev = &pdev->dev;
>>  	struct mtk_drm_private *private;
>> -	struct device_node *node;
>> +	struct device_node *node, *parent_node;
>>  	struct component_match *match = NULL;
>>  	int ret;
>>  	int i;
>> @@ -407,12 +409,23 @@ static int mtk_drm_probe(struct platform_device *pdev)
>>  	INIT_WORK(&private->commit.work, mtk_atomic_work);
>>  	private->data = of_device_get_match_data(dev);
>>  
>> -	private->config_regs = syscon_node_to_regmap(dev->of_node);
>> -	if (IS_ERR(private->config_regs))
>> -		return PTR_ERR(private->config_regs);
>> +	/* Check if called from mfd */
>> +	if (!dev->of_node) {
>> +		mmsys_private = dev_get_drvdata(pdev->dev.parent);
> 
> Why do you directly access parent's driver data? You just need the
> device node of mmsys, maybe you could refer to [1].
> 
> [1]
> https://elixir.free-electrons.com/linux/latest/source/drivers/reset/reset-berlin.c#L78
> 

The difference is, that the driver you mentioned gets probed via device tree
matching, while we get invoked here through the id_table. So there is no device
node (the if actually checkes for pdev->dev.of_node to identify exactly this case).

Regards,
Matthias