On Tue, 2015-12-15 at 13:45 +0800, Daniel Kurtz wrote:

Hi Yong,

On Tue, Dec 15, 2015 at 10:38 AM, Yong Wu [off-list ref] wrote:

quoted

On Mon, 2015-12-14 at 19:18 +0100, Matthias Brugger wrote:

quoted

On Tuesday 08 Dec 2015 17:49:11 Yong Wu wrote:

quoted

This patch add SMI(Smart Multimedia Interface) driver. This driver
is responsible to enable/disable iommu and control the power domain
and clocks of each local arbiter.

Signed-off-by: Yong Wu <yong.wu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
---
  Currently SMI offer mtk_smi_larb_get/put to enable the power-domain
,clocks and initialize the iommu configuration register for each a local
arbiter, The reason is:
  a) If a device would like to disable iommu, it also need call
mtk_smi_larb_get/put to enable its power and clocks.
  b) The iommu core don't support attach/detach a device within a
iommu-group. So we cann't use iommu_attach_device(iommu_detach_device)
instead
of mtk_smi_larb_get/put.

[..]

quoted

quoted

+static int
+mtk_smi_enable(struct device *dev, struct clk *apb, struct clk *smi)
+{
+   int ret;
+
+   ret = pm_runtime_get_sync(dev);
+   if (ret < 0)
+           return ret;
+
+   ret = clk_prepare_enable(apb);
+   if (ret)
+           goto err_put_pm;
+
+   ret = clk_prepare_enable(smi);
+   if (ret)
+           goto err_disable_apb;
+
+   return 0;
+
+err_disable_apb:
+   clk_disable_unprepare(apb);
+err_put_pm:
+   pm_runtime_put_sync(dev);
+   return ret;
+}
+
+static void
+mtk_smi_disable(struct device *dev, struct clk *apb, struct clk *smi)
+{
+   clk_disable_unprepare(smi);
+   clk_disable_unprepare(apb);
+   pm_runtime_put_sync(dev);
+}
+
+static int mtk_smi_common_enable(struct mtk_smi_common *common)
+{
+   return mtk_smi_enable(common->dev, common->clk_apb, common->clk_smi);
+}
+
+static void mtk_smi_common_disable(struct mtk_smi_common *common)
+{
+   mtk_smi_disable(common->dev, common->clk_apb, common->clk_smi);
+}
+
+static int mtk_smi_larb_enable(struct mtk_smi_larb *larb)
+{
+   return mtk_smi_enable(larb->dev, larb->clk_apb, larb->clk_smi);
+}
+
+static void mtk_smi_larb_disable(struct mtk_smi_larb *larb)
+{
+   mtk_smi_disable(larb->dev, larb->clk_apb, larb->clk_smi);
+}
+

This is somehow over-engineered. Just use mtk_smi_enable and mtk_smi_disable
instead of adding an extra indirection.

I added this only for readable...then the code in mtk_smi_larb_get below
may looks simple and readable.

If I use mtk_smi_enable/disable directly, the code will be like our
v5[1], is it OK?
Maybe I don't need these help function here, and only add more comment
based on v5.

[1]
http://lists.linuxfoundation.org/pipermail/iommu/2015-October/014590.html

bike-shedding...

I like the fact that Yong is trying to make his helpers more type-safe.
But, perhaps we can rename "struct mtk_smi_common" as "struct
mtk_smi", and then make "struct mtk_smi_larb" contain a "struct
mtk_smi":

struct mtk_smi {
  struct device *dev;
  struct clk *clk_apb, *clk_smi;
}

struct mtk_smi_larb {
  struct mtk_smi;
  ...
}


Then, have:

int mtk_smi_enable(struct mtk_smi *smi)
{
  clk_enable(smi->clk_apb);
  ...
}

int mtk_smi_disable(struct mtk_smi *smi)
{
}

int mtk_smi_larb_get(struct device *larbdev)
{
  struct mtk_smi_larb *larb = dev_get_drvdata(larbdev);
  struct mtk_smi *common = dev_get_drvdata(larb->smi_common_dev);

  mtk_smi_enable(common);
  mtk_smi_enable(&larb->smi);
  ...
}

Thanks. I will change like this in next time.

quoted

quoted

quoted

+int mtk_smi_larb_get(struct device *larbdev)
+{
+   struct mtk_smi_larb *larb = dev_get_drvdata(larbdev);
+   struct mtk_smi_common *common = dev_get_drvdata(larb->smi_common_dev);
+   int ret;
+
+   ret = mtk_smi_common_enable(common);
+   if (ret)
+           return ret;
+
+   ret = mtk_smi_larb_enable(larb);
+   if (ret)
+           goto err_put_smi;
+
+   /* Configure the iommu info */
+   writel_relaxed(larb->mmu, larb->base + SMI_LARB_MMU_EN);

I think this should probably be writel() not writel_relaxed, since you
really do want the barrier to ensure all other register accesses have
completed before enabling the MMU.

Yes. I will fix this.

quoted

quoted

quoted

+
+   return 0;
+
+err_put_smi:
+   mtk_smi_common_disable(common);
+   return ret;
+}
+
+void mtk_smi_larb_put(struct device *larbdev)
+{
+   struct mtk_smi_larb *larb = dev_get_drvdata(larbdev);
+   struct mtk_smi_common *common = dev_get_drvdata(larb->smi_common_dev);
+
+   writel_relaxed(0, larb->base + SMI_LARB_MMU_EN);
+   mtk_smi_larb_disable(larb);
+   mtk_smi_common_disable(common);
+}
+

Looks strange that you just disable all MMUs while you only enable some of
them at runtime. Unfortunately the datasheet I have lacks the SMI part, so I
can just guess how the HW is working.
From the DTS it looks like as if a larb can be used by two different
components (e.g. larb0 from ovl0 and rdma0). Wouldn't that produce a conflict?

Thanks. It's really a problem.

There are OVL0 and MDP in larb0, Both will call mtk_smi_larb_get/put, we
cann't disable all the MMUs in whole the larb0 here.  This register
should be reset to zero while the larb power domain turning off(rely on
the power-domain ref count).
I will delete this(keep this in our V5.)

Hmm, mtk_smi_config_port(.., false) clears the bit in larb->mmu, but
does not actually "disable" an enabled mmu.

Actually mtk_smi_config_port(.., false) will never be called currently.

If anybody would like to call iommu_detach_device to config-port false.
He will get the log below since the current iommu core don't support
detach one device in a iommu-group which have many devices.

That's to say that the larb->mmu is initialized in probe, and will never
be changed again.

(151119_13:39:37.472)WARNING:
at /proj/mtk40525/upstreamdev/v4.4/kernel/mediatek/drivers/iommu/iommu.c:1154
(151119_13:39:37.472)Modules linked in:
(151119_13:39:37.472)CPU: 1 PID: 731 Comm: sh Not tainted 4.4.0-rc1+ #37
(151119_13:39:37.472)Hardware name: MediaTek MT8173 evaluation board
(DT)
(151119_13:39:37.472)task: ffffffc076bb4d00 ti: ffffffc076bdc000
task.ti: ffffffc076bdc000
(151119_13:39:37.472)PC is at iommu_detach_device+0x5c/0xb0
(151119_13:39:37.472)LR is at iommu_detach_device+0x30/0xb0
...
(151119_13:39:37.550)---[ end trace d831cba9f811edf3 ]---
(151119_13:39:37.550)Call trace:
(151119_13:39:37.550)[<ffffffc0003f8c70>] iommu_detach_device+0x5c/0xb0

By the way, In the next version I plan to delete this interface
mtk_smi_config_port, use the additional data of the component-bind
instead of this.

The MMU will be disabled only on the next mtk_smi_larb_get() (for a
different port on the same larb).
I guess this is ok.  The only weird thing is this situation, where an
MMU can be left enabled when its user is done with it:

 /* configure port 0 as 'enabled' */
 mtk_smi_config_port(0, true);
 /* configure port 1 as 'enabled' */
 mtk_smi_config_port(1, true);

/* user of port 0 wants to do work */
mtk_smi_larb_get() /* turns on all clks, power & enables both MMUs */

/* user of port 1 wants to do work */
mtk_smi_larb_get()

/* user of port 1 done doing work */
mtk_smi_larb_put()

/* MMU 1 is still enabled */

This is really not so perfect in this case.

Even though the iommu-core support iommu-detach dynamically for our case
in the future(there is no plan currently), This don't have bad effect.

If user of port 1 want to work again, He should call mtk_smi_larb_get
again.

From the HW, there may be different modules in a local arbiter, SMI here

can not detect which module call mtk_smi_larb_put and disable his
special iommu bits. After all mtk_smi_larb_put is mainly for power off
and disable the clocks.

Thanks!
-Dan

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