Re: [PATCH v7 2/4] soc: mediatek: Init MT8173 scpsys driver earlier
From: Matthias Brugger
Date: Wed Oct 26 2016 - 10:55:03 EST
Hi Yong,
On 07/12/2016 11:01 AM, Yong Wu wrote:
Hi Matthias,
On Fri, 2016-07-08 at 14:47 +0200, Matthias Brugger wrote:
On 06/07/16 07:22, James Liao wrote:
On Sat, 2016-07-02 at 18:35 +0200, Matthias Brugger wrote:
On 05/16/2016 11:28 AM, James Liao wrote:
Some power domain comsumers may init before module_init.
So the power domain provider (scpsys) need to be initialized
earlier too.
Take an example for our IOMMU (M4U) and SMI. SMI is a bridge
between IOMMU and multimedia HW. SMI is responsible to
enable/disable iommu and help transfer data for each multimedia
HW. Both of them have to wait until the power and clocks are
enabled.
So scpsys driver should be initialized before SMI, and SMI should
be initialized before IOMMU, and then init IOMMU consumers
(display/vdec/venc/camera etc.).
IOMMU is subsys_init by default. So we need to init scpsys driver
before subsys_init.
Signed-off-by: James Liao <jamesjj.liao@xxxxxxxxxxxx>
Reviewed-by: Kevin Hilman <khilman@xxxxxxxxxxxx>
---
drivers/soc/mediatek/mtk-scpsys.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
index 5870a24..00c0adb 100644
--- a/drivers/soc/mediatek/mtk-scpsys.c
+++ b/drivers/soc/mediatek/mtk-scpsys.c
@@ -617,4 +617,21 @@ static struct platform_driver scpsys_drv = {
.of_match_table = of_match_ptr(of_scpsys_match_tbl),
},
};
-builtin_platform_driver(scpsys_drv);
+
+static int __init scpsys_drv_init(void)
+{
+ return platform_driver_register(&scpsys_drv);
+}
+
+/*
+ * There are some Mediatek drivers which depend on the power domain driver need
+ * to probe in earlier initcall levels. So scpsys driver also need to probe
+ * earlier.
+ *
+ * IOMMU(M4U) and SMI drivers for example. SMI is a bridge between IOMMU and
+ * multimedia HW. IOMMU depends on SMI, and SMI is a power domain consumer,
+ * so the proper probe sequence should be scpsys -> SMI -> IOMMU driver.
+ * IOMMU drivers are initialized during subsys_init by default, so we need to
+ * move SMI and scpsys drivers to subsys_init or earlier init levels.
+ */
+subsys_initcall(scpsys_drv_init);
Can't we achieve this with probe deferring? I'm not really keen on
coding the order of the different drivers like this.
Hi Matthias,
Some drivers such as IOMMU don't support probe deferring. So scpsys need
to init before them by changing init level.
SMI larbs return EPROBE_DEFER if it can't find the PM provider for it's
domain, so this part should not be the problem. The larbs get added as
components in the probe, when the PM provider is present.
The iommu driver uses the larbs as components. As long as not all
components are present the iommu does not bind them. So from what I see
this should work without any problem.
Can you please specify where the iommu dirver has a problem. Maybe we
need to fix the driver rather then scpsys.
We got a problem while bootup, the hang backtrace is like below(Sorry, I
can't find the full backtrace now):
[ 7.832359] Call trace:
[ 7.834778] [<ffffffc000764424>] mtk_smi_larb_get+0x24/0xa8
[ 7.840300] [<ffffffc0005a1390>] mtk_drm_crtc_enable+0x6c/0x450
The reason is that "larb->mmu" is NULL while DRM call mtk_smi_larb_get.
DRM call iommu_present to wait for whether IOMMU is ready[1].
But in the MTK-IOMMU, It will call
bus_set_iommu->mtk_iommu_add_device->mtk_iommu_attach_device, then it's
able to transfer "struct mtk_smi_iommu" to SMI whose probe maybe delayed
by power-domain, then SMI could finish its probe.
So If DRM probe is called after the time of calling bus_set_iommu and
before the time of SMI probe finish, this problem can be reproduced.
The root cause is that iommu_present cann't indicate that MTK-IOMMU and
SMI is ready actually. in other words, the DRM cann't detect
whether the SMI has probed done.
If we move scpsys_init from module_initcall to subsys_initcall, the
IOMMU and SMI could be probe done during the subsys_initcall period.
this issue can be avoid.
And as we grep before, there are also some examples whose power-domain
is also not module_init[2].
core_initcall(exynos4_pm_init_power_domain);
subsys_initcall(imx_pgc_init);
If you think that this patch will hide the problem above, then I have to
add a new function, like below:
//==================
bool mtk_smi_larb_ready(struct device *larbdev)
{
struct mtk_smi_larb *larb = dev_get_drvdata(larbdev);
return larb && !!larb->mmu;
}
//=================
And in the probe of all the MTK-IOMMU consumer, we have to add this:
//====================
if (!mtk_smi_larb_ready(&larb_pdev->dev))
return -EPROBE_DEFER;
//====================
The sequence is a little complex, If I don't explain clearly, please
tell me.
Any other suggestion about this? Thanks.
I'm still trying to find a different way to solve this. Unfortunately
I'm not able to reproduce this on my mt8173-evb...
...but: iommu_present checkes if the bus->iommu_ops is set. If we set
these option in the iommu after all components got initialized, we
should be fine. Or did I miss something?
Would you mind trying the patch below (against v4.9-rc1)?
If you know of any way to reproduce this issue, I would be happy to know.
I'm adding Joerg, the iommu maintainer, maybe he has an idea.
Thanks a lot,
Matthias
diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index b12c12d..9249011 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -602,10 +602,12 @@ static int mtk_iommu_probe(struct platform_device
*pdev)
if (ret)
return ret;
- if (!iommu_present(&platform_bus_type))
+ ret = component_master_add_with_match(dev, &mtk_iommu_com_ops,
match);
+
+ if (ret && !iommu_present(&platform_bus_type))
bus_set_iommu(&platform_bus_type, &mtk_iommu_ops);
- return component_master_add_with_match(dev, &mtk_iommu_com_ops,
match);
+ return ret;
}
static int mtk_iommu_remove(struct platform_device *pdev)