Re: [PATCH v8 04/12] iommu/mediatek: Add device_link between the consumer and the larb devices

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

On 16.10.21 04:23, Yong Wu wrote:
> On Mon, 2021-10-11 at 14:36 +0200, Dafna Hirschfeld wrote:
>>
>> On 29.09.21 03:37, Yong Wu wrote:
>>> MediaTek IOMMU-SMI diagram is like below. all the consumer connect
>>> with
>>> smi-larb, then connect with smi-common.
>>>
>>>           M4U
>>>            |
>>>       smi-common
>>>            |
>>>     -------------
>>>     |         |    ...
>>>     |         |
>>> larb1     larb2
>>>     |         |
>>> vdec       venc
>>>
>>> When the consumer works, it should enable the smi-larb's power
>>> which
>>> also need enable the smi-common's power firstly.
>>>
>>> Thus, First of all, use the device link connect the consumer and
>>> the
>>> smi-larbs. then add device link between the smi-larb and smi-
>>> common.
>>>
>>> This patch adds device_link between the consumer and the larbs.
>>>
>>> When device_link_add, I add the flag DL_FLAG_STATELESS to avoid
>>> calling
>>> pm_runtime_xx to keep the original status of clocks. It can avoid
>>> two
>>> issues:
>>> 1) Display HW show fastlogo abnormally reported in [1]. At the
>>> beggining,
>>> all the clocks are enabled before entering kernel, but the clocks
>>> for
>>> display HW(always in larb0) will be gated after clk_enable and
>>> clk_disable
>>> called from device_link_add(->pm_runtime_resume) and rpm_idle. The
>>> clock
>>> operation happened before display driver probe. At that time, the
>>> display
>>> HW will be abnormal.
>>>
>>> 2) A deadlock issue reported in [2]. Use DL_FLAG_STATELESS to skip
>>> pm_runtime_xx to avoid the deadlock.
>>>
>>> Corresponding, DL_FLAG_AUTOREMOVE_CONSUMER can't be added, then
>>> device_link_removed should be added explicitly.
>>>
>>> [1]
>>> https://lore.kernel.org/linux-mediatek/1564213888.22908.4.camel@mhfsdcap03/
>>> [2] https://lore.kernel.org/patchwork/patch/1086569/
>>>
>>> Suggested-by: Tomasz Figa <tfiga@chromium.org>
>>> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
>>> Tested-by: Frank Wunderlich <frank-w@public-files.de> # BPI-
>>> R2/MT7623
>>> ---
>>>    drivers/iommu/mtk_iommu.c    | 22 ++++++++++++++++++++++
>>>    drivers/iommu/mtk_iommu_v1.c | 20 +++++++++++++++++++-
>>>    2 files changed, 41 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>>> index d5848f78a677..a2fa55899434 100644
>>> --- a/drivers/iommu/mtk_iommu.c
>>> +++ b/drivers/iommu/mtk_iommu.c
>>> @@ -560,22 +560,44 @@ static struct iommu_device
>>> *mtk_iommu_probe_device(struct device *dev)
>>>    {
>>>    	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>>>    	struct mtk_iommu_data *data;
>>> +	struct device_link *link;
>>> +	struct device *larbdev;
>>> +	unsigned int larbid;
>>>    
>>>    	if (!fwspec || fwspec->ops != &mtk_iommu_ops)
>>>    		return ERR_PTR(-ENODEV); /* Not a iommu client device
>>> */
>>>    
>>>    	data = dev_iommu_priv_get(dev);
>>>    
>>> +	/*
>>> +	 * Link the consumer device with the smi-larb device(supplier)
>>> +	 * The device in each a larb is a independent HW. thus only
>>> link
>>> +	 * one larb here.
>>> +	 */
>>> +	larbid = MTK_M4U_TO_LARB(fwspec->ids[0]);
>>
>> so larbid is always the same for all the ids of a device?
> 
> Yes. For me, each a dtsi node should represent a HW unit which can only
> connect one larb.
> 
>> If so maybe it worth testing it and return error if this is not the
>> case.
> 
> Thanks for the suggestion. This is very helpful. I did see someone put
> the different larbs in one node. I will check this, and add return

I am working on bugs found on media drivers, could you please point me to
that wrong node?
Will you send a fix to that node in the dtsi?


Thanks,
Dafna

> EINVAL for this case.



> 
>>
>> Thanks,
>> Dafna
>   
>>>