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Subject: Re: [PATCH] drm/rockchip: Check iommu itself instead of it's parent
 for device_is_available
To:     Robin Murphy <robin.murphy@arm.com>, hjc@rock-chips.com,
        heiko@sntech.de, dri-devel@lists.freedesktop.org,
        linux-rockchip@lists.infradead.org
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20210627084737.309163-1-andy.yan@rock-chips.com>
 <66fb4977-4e6f-f7ed-0dac-18710ebd782a@arm.com>
From:   Andy Yan <andy.yan@rock-chips.com>
Message-ID: <f20e1547-649e-2d9b-cd90-7b8291d505a6@rock-chips.com>
Date:   Tue, 29 Jun 2021 19:18:29 +0800
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Hi Robin:

On 6/28/21 5:54 PM, Robin Murphy wrote:
> On 2021-06-27 09:47, Andy Yan wrote:
>> When iommu itself is disabled in dts, we should
>> fallback to non-iommu buffer, check iommu parent
>> is meanless here.
>>
>> Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
>> ---
>>
>>   drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c 
>> b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> index 212bd87c0c4a..0d20c8cc1ffa 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> @@ -366,7 +366,7 @@ static int rockchip_drm_platform_of_probe(struct 
>> device *dev)
>>           }
>>             iommu = of_parse_phandle(port->parent, "iommus", 0);
>> -        if (!iommu || !of_device_is_available(iommu->parent)) {
>> +        if (!iommu || !of_device_is_available(iommu)) {
>
> Just wondering, could you use device_iommu_mapped() to avoid poking at 
> the DT at all here, or is it that you need to check remote graph 
> endpoints whose struct device may not be ready yet?


device_iommu_mapped(dev)  can't be called from rockchip_drm_init_iommu, 
as there is no  iommu dev(vop) in these function.

>
> Robin.
>
>>               DRM_DEV_DEBUG(dev,
>>                         "no iommu attached for %pOF, using non-iommu 
>> buffers\n",
>>                         port->parent);
>>
>
>
>