Messages in this thread | | | Subject | Re: [PATCH 1/2] iommu/mediatek: Always tlb_flush_all when each PM resume | From | Dafna Hirschfeld <> | Date | Wed, 8 Dec 2021 11:50:04 +0200 |
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On 07.12.21 10:31, Dafna Hirschfeld wrote: > > > On 27.11.21 04:46, Yong Wu wrote: >> Hi Dafna, >> >> Sorry for reply late. >> >> On Mon, 2021-11-22 at 12:43 +0200, Dafna Hirschfeld wrote: >>> From: Yong Wu <yong.wu@mediatek.com> >>> >>> Prepare for 2 HWs that sharing pgtable in different power-domains. >>> >>> When there are 2 M4U HWs, it may has problem in the flush_range in >>> which >>> we get the pm_status via the m4u dev, BUT that function don't reflect >>> the >>> real power-domain status of the HW since there may be other HW also >>> use >>> that power-domain. >>> >>> The function dma_alloc_attrs help allocate the iommu buffer which >>> need the corresponding power domain since tlb flush is needed when >>> preparing iova. BUT this function only is for allocating buffer, >>> we have no good reason to request the user always call pm_runtime_get >>> before calling dma_alloc_xxx. Therefore, we add a tlb_flush_all >>> in the pm_runtime_resume to make sure the tlb always is clean. >>> >>> Another solution is always call pm_runtime_get in the >>> tlb_flush_range. >>> This will trigger pm runtime resume/backup so often when the iommu >>> power is not active at some time(means user don't call pm_runtime_get >>> before calling dma_alloc_xxx), This may cause the performance drop. >>> thus we don't use this. >>> >>> In other case, the iommu's power should always be active via device >>> link with smi. >>> >>> The previous SoC don't have PM except mt8192. the mt8192 IOMMU is >>> display's >>> power-domain which nearly always is enabled. thus no need fix tags >>> here. >>> Prepare for mt8195. >> >> In this patchset, this message should be not proper. I think you could >> add the comment why this patch is needed in mt8173. >> >>> >>> Signed-off-by: Yong Wu <yong.wu@mediatek.com> >>> [imporvie inline doc] >>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com> >>> --- >>> drivers/iommu/mtk_iommu.c | 7 +++++++ >>> 1 file changed, 7 insertions(+) >>> >>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c >>> index 25b834104790..28dc4b95b6d9 100644 >>> --- a/drivers/iommu/mtk_iommu.c >>> +++ b/drivers/iommu/mtk_iommu.c >>> @@ -964,6 +964,13 @@ static int __maybe_unused >>> mtk_iommu_runtime_resume(struct device *dev) >>> return ret; >>> } >>> + /* >>> + * Users may allocate dma buffer before they call >>> pm_runtime_get, >>> + * in which case it will lack the necessary tlb flush. >>> + * Thus, make sure to update the tlb after each PM resume. >>> + */ >>> + mtk_iommu_tlb_flush_all(data); >> >> This should not work. since current the *_tlb_flush_all call >> pm_runtime_get_if_in_use which will always return 0 when it called from >> this runtime_cb in my test. thus, It won't do the tlb_flush_all >> actually.
He, indeed, my mistake, although the encoder works more or less fine even without the full flush so I didn't catch that.
>> >> I guess this also depend on these two patches of mt8195 v3. >> [PATCH v3 09/33] iommu/mediatek: Remove for_each_m4u in tlb_sync_all >> [PATCH v3 10/33] iommu/mediatek: Add tlb_lock in tlb_flush_all
I'll add those two
>> >> like in [10/33], I added a mtk_iommu_tlb_do_flush_all which don't have >> the pm operation.
yes, I need to remove the pm_runtime_get_if_in_use call in the 'flush_all' func I see there is also a patch for that in the mt8195 v3 series "[PATCH v3 13/33] iommu/mediatek: Remove the power status checking in tlb flush all"
So I'll send v2, adding all those 3 patches, but I think adding mtk_iommu_tlb_do_flush_all on patch 9 and removing it again on patch 13 is confusing so I'll avoid that.
Thanks, Dafna
>> >> This looks has a dependence. Let me know if I can help this. > > It did work for me, testing on elm device. I'll check that again. > > >> >>> + >>> /* >>> * Uppon first resume, only enable the clk and return, since >>> the values of the >>> * registers are not yet set. >
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