Re: [PATCH v3 13/33] iommu/mediatek: Remove the power status checking in tlb flush all
From: Dafna Hirschfeld <hidden>
Date: 2021-10-22 14:03:28
Also in:
linux-arm-kernel, linux-iommu, linux-mediatek, lkml
Hi On 23.09.21 13:58, Yong Wu wrote:
To simplify the code, Remove the power status checking in the
tlb_flush_all, remove this:
if (pm_runtime_get_if_in_use(data->dev) <= 0)
continue;
After this patch, the mtk_iommu_tlb_flush_all will be called from
a) isr
b) pm runtime resume callback
c) tlb flush range fail case
d) iommu_create_device_direct_mappings
-> iommu_flush_iotlb_all
In first three cases, the power and clock always are enabled; d) is directRegarding case "c) tlb flush range fail case", I found out that this often happens when the iommu is used while it is runtime suspended. For example the mtk-vcodec encoder driver calls "pm_runtime_resume_and_get" only when it starts streaming but buffers allocation is done in 'v4l2_reqbufs' before "pm_runtime_resume_and_get" is called and then I see the warning "Partial TLB flush timed out, falling back to full flush" I am not sure how to fix that issue, but it seems that case 'c)' might indicate that power and clock are actually not enabled.
quoted hunk ↗ jump to hunk
mapping, the tlb flush is unnecessay since we already have tlb_flush_all in the pm_runtime_resume callback. When the iommu's power status is changed to active, the tlb always is clean. In addition, there still are 2 reasons that don't add PM status checking in the tlb flush all: a) Write tlb flush all register also is ok even though the HW has no power and clocks. Write ignore. b) pm_runtime_get_if_in_use(m4udev) is 0 when the tlb_flush_all is called frm pm_runtime_resume cb. From this point, we can not add this code above in this tlb_flush_all. Signed-off-by: Yong Wu <yong.wu@mediatek.com> --- drivers/iommu/mtk_iommu.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-)diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c index e9e94944ed91..4a33b6c6b1db 100644 --- a/drivers/iommu/mtk_iommu.c +++ b/drivers/iommu/mtk_iommu.c@@ -204,10 +204,14 @@ static struct mtk_iommu_domain *to_mtk_domain(struct iommu_domain *dom) return container_of(dom, struct mtk_iommu_domain, domain); } -static void mtk_iommu_tlb_do_flush_all(struct mtk_iommu_data *data) +static void mtk_iommu_tlb_flush_all(struct mtk_iommu_data *data) { unsigned long flags; + /* + * No need get power status since the HW PM status nearly is active + * when entering here. + */ spin_lock_irqsave(&data->tlb_lock, flags); writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0, data->base + data->plat_data->inv_sel_reg);@@ -216,16 +220,6 @@ static void mtk_iommu_tlb_do_flush_all(struct mtk_iommu_data *data) spin_unlock_irqrestore(&data->tlb_lock, flags); } -static void mtk_iommu_tlb_flush_all(struct mtk_iommu_data *data) -{ - if (pm_runtime_get_if_in_use(data->dev) <= 0) - return; - - mtk_iommu_tlb_do_flush_all(data); - - pm_runtime_put(data->dev); -} - static void mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size, struct mtk_iommu_data *data) {@@ -263,7 +257,7 @@ static void mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size, if (ret) { dev_warn(data->dev, "Partial TLB flush timed out, falling back to full flush\n"); - mtk_iommu_tlb_do_flush_all(data); + mtk_iommu_tlb_flush_all(data); } if (has_pm)@@ -993,7 +987,7 @@ static int __maybe_unused mtk_iommu_runtime_resume(struct device *dev) * * Thus, Make sure the tlb always is clean after each PM resume. */ - mtk_iommu_tlb_do_flush_all(data); + mtk_iommu_tlb_flush_all(data); /* * Uppon first resume, only enable the clk and return, since the values of the