Re: [PATCH v5 06/27] dt-bindings: mediatek: Add binding for mt8192 IOMMU

Yong Wu
2020-12-24T11:36:27Z

On Wed, 2020-12-23 at 17:18 +0900, Tomasz Figa wrote:
> On Wed, Dec 09, 2020 at 04:00:41PM +0800, Yong Wu wrote:
> > This patch adds decriptions for mt8192 IOMMU and SMI.
> >
> > mt8192 also is MTK IOMMU gen2 which uses ARM Short-Descriptor translation
> > table format. The M4U-SMI HW diagram is as below:
> >
> > EMI
> > |
> > M4U
> > |
> > ------------
> > SMI Common
> > ------------
> > |
> > +-------+------+------+----------------------+-------+
> > | | | | ...... | |
> > | | | | | |
> > larb0 larb1 larb2 larb4 ...... larb19 larb20
> > disp0 disp1 mdp vdec IPE IPE
> >
> > All the connections are HW fixed, SW can NOT adjust it.
> >
> > mt8192 M4U support 0~16GB iova range. we preassign different engines
> > into different iova ranges:
> >
> > domain-id module iova-range larbs
> > 0 disp 0 ~ 4G larb0/1
> > 1 vcodec 4G ~ 8G larb4/5/7
> > 2 cam/mdp 8G ~ 12G larb2/9/11/13/14/16/17/18/19/20
>
> Why do we preassign these addresses in DT? Shouldn't it be a user's or
> integrator's decision to split the 16 GB address range into sub-ranges
> and define which larbs those sub-ranges are shared with?

The problem is that we can't split the 16GB range with the larb as unit.
The example is the below ccu0(larb13 port9/10) is a independent
range(domain), the others ports in larb13 is in another domain.

disp/vcodec/cam/mdp don't have special iova requirement, they could
access any range. vcodec also can locate 8G~12G. it don't care about
where its iova locate. here I preassign like this following with our
internal project setting.

Why set this in DT?, this is only for simplifying the code. Assume we
put it in the platform data. We have up to 32 larbs, each larb has up to
32 ports, each port may be in different iommu domains. we should have a
big array for this..however we only use a macro to get the domain in the
DT method.

When replying this mail, I happen to see there is a "dev->dev_range_map"
which has "dma-range" information, I think I could use this value to get
which domain the device belong to. then no need put domid in DT. I will
test this.

Thanks.
>
> Best regards,
> Tomasz
>
> > 3 CCU0 0x4000_0000 ~ 0x43ff_ffff larb13: port 9/10
> > 4 CCU1 0x4400_0000 ~ 0x47ff_ffff larb14: port 4/5
> >
> > The iova range for CCU0/1(camera control unit) is HW requirement.
> >
> > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> > Reviewed-by: Rob Herring <robh@kernel.org>
> > ---
> > .../bindings/iommu/mediatek,iommu.yaml | 18 +-
> > include/dt-bindings/memory/mt8192-larb-port.h | 240 ++++++++++++++++++
> > 2 files changed, 257 insertions(+), 1 deletion(-)
> > create mode 100644 include/dt-bindings/memory/mt8192-larb-port.h
> >
[snip]