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

[Dafna Hirschfeld]

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@xxxxxxxxxxxx>
> > > Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
> > > Tested-by: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx> # 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
>   
> > >