Re: [PATCH v3 09/33] iommu/mediatek: Remove for_each_m4u in tlb_sync_all

[AngeloGioacchino Del Regno]

Il 10/01/22 11:59, Yong Wu ha scritto:
> On Mon, 2022-01-10 at 10:16 +0100, AngeloGioacchino Del Regno wrote:
> > Il 09/01/22 03:48, Yong Wu ha scritto:
> > > On Tue, 2022-01-04 at 16:55 +0100, AngeloGioacchino Del Regno
> > > wrote:
> > > > Il 23/09/21 13:58, Yong Wu ha scritto:
> > > > > The tlb_sync_all is called from these three functions:
> > > > > a) flush_iotlb_all: it will be called for each a iommu HW.
> > > > > b) tlb_flush_range_sync: it already has for_each_m4u.
> > > > > c) in irq: When IOMMU HW translation fault, Only need flush
> > > > > itself.
> > > > >
> > > > > Thus, No need for_each_m4u in this tlb_sync_all. Remove it.
> > > > >
> > > > > Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
> > > > > ---
> > > > >     drivers/iommu/mtk_iommu.c | 18 +++++++-----------
> > > > >     1 file changed, 7 insertions(+), 11 deletions(-)
> > > > >
> > > > > diff --git a/drivers/iommu/mtk_iommu.c
> > > > > b/drivers/iommu/mtk_iommu.c
> > > > > index 6f4f6624e3ac..0b4c30baa864 100644
> > > > > --- a/drivers/iommu/mtk_iommu.c
> > > > > +++ b/drivers/iommu/mtk_iommu.c
> > > > > @@ -206,19 +206,15 @@ static struct mtk_iommu_domain
> > > > > *to_mtk_domain(struct iommu_domain *dom)
> > > > >     
> > > > >     static void mtk_iommu_tlb_flush_all(struct mtk_iommu_data
> > > > > *data)
> > > > >     {
> > > > > -	struct list_head *head = data->hw_list;
> > > > > -
> > > > > -	for_each_m4u(data, head) {
> > > > > -		if (pm_runtime_get_if_in_use(data->dev) <= 0)
> > > > > -			continue;
> > > > > +	if (pm_runtime_get_if_in_use(data->dev) <= 0)
> > > > > +		return;
> > > > >     
> > > > > -		writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
> > > > > -			       data->base + data->plat_data-
> > > > > > inv_sel_reg);
> > > > >
> > > > > -		writel_relaxed(F_ALL_INVLD, data->base +
> > > > > REG_MMU_INVALIDATE);
> > > > > -		wmb(); /* Make sure the tlb flush all done */
> > > > > +	writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
> > > > > +		       data->base + data->plat_data-
> > > > > > inv_sel_reg);
> > > > > +	writel_relaxed(F_ALL_INVLD, data->base +
> > > > > REG_MMU_INVALIDATE);
> > > > > +	wmb(); /* Make sure the tlb flush all done */
> > > >
> > > > There aren't a lot of writes here - not anymore, since you are no
> > > > longer doing
> > > > this for_each_m4u()...
> > > > ...so, please change writel_relaxed() to writel() calls, allowing
> > > > you
> > > > to also
> > > > remove the write barrier at the end (since in the non relaxed
> > > > version, order is already ensured).
> > >
> > > In the "writel", the "__iowmb()" runs before "write_relaxed". Then
> > > how
> > > to guarantee the last register was wrote into the HW. Here the
> > > flush
> > > all don't have sync(waiting it complete)
> >
> > That's right, I'm sorry for the invalid proposal.
> >
> > Though, there's something else to mention here... if writing
> > (F_INVLD_EN1 | F_INVLD_EN0) to inv_sel_reg is *required* to happen
> > before
> > writing F_ALL_INVLD to REG_MMU_INVALIDATE (which I think is exactly
> > the
> > case here), then, in order to ensure write ordering, you should still
> > use
> > writel() instead of the relaxed accessor; after which, since (as you
> > mentioned)
> > there is no sync readback loop, you can keep that wmb() at the end.
>
> The writel_relaxed also makes sure the order. I did try this:
>
>
> https://patchwork.kernel.org/project/linux-mediatek/patch/1570627143-29441-3-git-send-email-yong.wu@xxxxxxxxxxxx/

Ok, that's fair. Means that this patch is fine as it is.
I'll release by R-b on Dafna's patch, as suggested.

Thank you,
- Angelo