On Thu, 2020-11-26 at 16:43 +0000, Robin Murphy wrote:

On 2020-11-11 12:38, Yong Wu wrote:

quoted

In attach device, it will update the pagetable base address register.
Move the hw_init function also here. Then it only need call
pm_runtime_get/put one time here if m4u has power domain.

Doesn't that mean you'll end up writing most of the registers twice 
every time? (first from mtk_iommu_resume(), then again from 
mtk_iommu_hw_init())

I have skipped the first resume from mtk_iommu_resume with the code in
[15/24]:

@@ -828,6 +848,9 @@ static int __maybe_unused

mtk_iommu_runtime_resume(struct device *dev)

+/* Avoid first resume to affect the default value of registers below.*/
+if (!m4u_dom)
+   return 0;

It might be neater to have mtk_iommu_hw_init() simply populate the 
mtk_iommu_suspend_reg data with the initial values at probe time and 
manually call mtk_iommu_resume() if the hardware is already powered up 
at that point. Or maybe just don't bother saving those registers on 

Yes. All the power-domains are enabled in lk when bootup.

Actually I have plan to remove the pm_runtime_get in this attach_device
in the later patchset.

This is for fixing a issue that the screen is turned off when bootup.
In android project. we always show boot image. If iommu call
pm_runtime_get/put here, the display power-domain will be turned off
here given that iommu always probe before display drivers and iommu's
power-domain always is display's power-domain.

Even I plan to move the device's pm_runtime_enable into this
attach_device in the case all the drivers(iommu and display...) build as
modules. it is for skipping turn off display's power-domain in
genpd_power_off_unused.

This is only a plan, I'm not sure if power-domain could fix it like[1].

In this patchset, I'd like to keep current status.

[1]
https://patchwork.kernel.org/project/linux-clk/patch/20190630150230.7878-3-robdclark@gmail.com/

suspend and put the initialisation directly in the resume path.

Robin.

quoted

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
---
  drivers/iommu/mtk_iommu.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 55f9b329e637..cfdf5ce696fd 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c

@@ -125,6 +125,8 @@ struct mtk_iommu_domain {
  
  static const struct iommu_ops mtk_iommu_ops;
  
+static int mtk_iommu_hw_init(const struct mtk_iommu_data *data);
+
  /*
   * In M4U 4GB mode, the physical address is remapped as below:
   *

@@ -380,12 +382,16 @@ static int mtk_iommu_attach_device(struct iommu_domain *domain,
  {
  	struct mtk_iommu_data *data = dev_iommu_priv_get(dev);
  	struct mtk_iommu_domain *dom = to_mtk_domain(domain);
+	int ret;
  
  	if (!data)
  		return -ENODEV;
  
  	/* Update the pgtable base address register of the M4U HW */
  	if (!data->m4u_dom) {
+		ret = mtk_iommu_hw_init(data);
+		if (ret)
+			return ret;
  		data->m4u_dom = dom;
  		writel(dom->cfg.arm_v7s_cfg.ttbr & MMU_PT_ADDR_MASK,
  		       data->base + REG_MMU_PT_BASE_ADDR);

@@ -729,10 +735,6 @@ static int mtk_iommu_probe(struct platform_device *pdev)
  
  	platform_set_drvdata(pdev, data);
  
-	ret = mtk_iommu_hw_init(data);
-	if (ret)
-		return ret;
-
  	ret = iommu_device_sysfs_add(&data->iommu, dev, NULL,
  				     "mtk-iommu.%pa", &ioaddr);
  	if (ret)

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