[PATCH v1 3/4] media: mtk-mdp: don't pm_run_time_get/put for master comp in clock_on

Eizan Miyamoto
2021-04-23T06:03:22Z

The original intent of commit 86698b9505bbc ("media: mtk-mdp: convert
mtk_mdp_dev.comp array to list") was to create a list to track all the
MDP components that needed to have their clocks enabled/disabled when
calling mtk_mdp_comp_clock_on/off. However, there was a bug inside
mtk_mdp_register_component where the args to a call to list_add were
swapped. The result is that only one component was added to
mtk_mdp_dev.comp_list because comp_list was instead being
repeatedly added to the single element lists headed by each
mtk_mdp_comp.

The order of the args to list_add in mtk_mdp_register_component was
fixed in https://patchwork.kernel.org/patch/11742895/ (Fix Null pointer
dereference when calling list_add).

Then, as a result of https://patchwork.kernel.org/patch/11530769/
(mtk-mdp: use pm_runtime in MDP component driver) if all the components
are added to the component list, the mdp "master" / rdma0 component
ends up having pm_runtime_get_sync() called on it twice recursively:

rpm_resume+0x694/0x8f8
__pm_runtime_resume+0x7c/0xa0 ***NOTE***
mtk_mdp_comp_clock_on+0x48/0x104 [mtk_mdp]
mtk_mdp_pm_resume+0x2c/0x44 [mtk_mdp]
pm_generic_runtime_resume+0x34/0x48
__genpd_runtime_resume+0x6c/0x80
genpd_runtime_resume+0x104/0x1ac
__rpm_callback+0x120/0x238
rpm_callback+0x34/0x8c
rpm_resume+0x7a0/0x8f8
__pm_runtime_resume+0x7c/0xa0 ***NOTE***
mtk_mdp_m2m_start_streaming+0x2c/0x3c [mtk_mdp]

(The calls to pm_runtime_get_sync are inlined and correspond to the
calls to __pm_runtime_resume). It is not correct to have
pm_runtime_get_sync called recursively and the second call will block
indefinitely.

As a result of all that, this change factors mtk_mdp_comp_clock_on/off
into mtk_mdp_comp_power_on/off and moves the calls to
pm_runtime_get/put into the power_on/off functions.

This change then special-cases the master/rdma0 MDP component and does
these things:
- the master/rdma0 component is not added to mtk_mdp_dev.comp_list
- the master/rdma0 component has its clocks (*but not power*) toggled
by mtk_mpd_comp_clock_on/off inside mtk_mdp_clock_on/off.
- the other components have their clocks *and* power toggled with
mtk_mdp_comp_power_on/off.

This change introduces the assumption that mtk_mdp_pm_resume will
always be called though a callback from pm_runtime_get_sync made on the
master / rdma0 component.

Signed-off-by: Eizan Miyamoto <eizan@chromium.org>
---

drivers/media/platform/mtk-mdp/mtk_mdp_comp.c | 28 ++++++++++++++-----
drivers/media/platform/mtk-mdp/mtk_mdp_comp.h | 3 ++
drivers/media/platform/mtk-mdp/mtk_mdp_core.c | 23 ++++++++++-----
3 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
index 84f9c529d74a..d447bfaadef4 100644
--- a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
+++ b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
@@ -53,15 +53,31 @@ static const struct of_device_id mtk_mdp_comp_driver_dt_match[] = {
};
MODULE_DEVICE_TABLE(of, mtk_mdp_comp_driver_dt_match);

-void mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
+void mtk_mdp_comp_power_on(struct mtk_mdp_comp *comp)
{
- int i, err;
+ int err;

err = pm_runtime_get_sync(comp->dev);
if (err < 0)
- dev_err(comp->dev,
- "failed to runtime get, err %d.\n",
- err);
+ dev_err(comp->dev, "failed to runtime get, err %d.\n", err);
+
+ mtk_mdp_comp_clock_on(comp);
+}
+
+void mtk_mdp_comp_power_off(struct mtk_mdp_comp *comp)
+{
+ int err;
+
+ mtk_mdp_comp_clock_off(comp);
+
+ err = pm_runtime_put_sync(comp->dev);
+ if (err < 0)
+ dev_err(comp->dev, "failed to runtime put, err %d.\n", err);
+}
+
+void mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
+{
+ int i, err;

for (i = 0; i < ARRAY_SIZE(comp->clk); i++) {
if (IS_ERR(comp->clk[i]))
@@ -83,8 +99,6 @@ void mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp)
continue;
clk_disable_unprepare(comp->clk[i]);
}
-
- pm_runtime_put_sync(comp->dev);
}

static int mtk_mdp_comp_bind(struct device *dev, struct device *master,
diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
index 355e226d74fe..7ad9b06bb11b 100644
--- a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
+++ b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
@@ -21,6 +21,9 @@ struct mtk_mdp_comp {

int mtk_mdp_comp_init(struct mtk_mdp_comp *comp, struct device *dev);

+void mtk_mdp_comp_power_on(struct mtk_mdp_comp *comp);
+void mtk_mdp_comp_power_off(struct mtk_mdp_comp *comp);
+
void mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp);
void mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp);

diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
index c55bcfe4cbb7..5e71496e2517 100644
--- a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
+++ b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
@@ -53,8 +53,15 @@ static void mtk_mdp_clock_on(struct mtk_mdp_dev *mdp)
{
struct mtk_mdp_comp *comp_node;

+ /*
+ * The master / rdma0 component will have pm_runtime_get_sync called
+ * on it through mtk_mdp_m2m_start_streaming, making it unnecessary to
+ * have mtk_mdp_comp_power_on called on it.
+ */
+ mtk_mdp_comp_clock_on(&mdp->comp_self);
+
list_for_each_entry(comp_node, &mdp->comp_list, node)
- mtk_mdp_comp_clock_on(comp_node);
+ mtk_mdp_comp_power_on(comp_node);
}

static void mtk_mdp_clock_off(struct mtk_mdp_dev *mdp)
@@ -62,7 +69,14 @@ static void mtk_mdp_clock_off(struct mtk_mdp_dev *mdp)
struct mtk_mdp_comp *comp_node;

list_for_each_entry(comp_node, &mdp->comp_list, node)
- mtk_mdp_comp_clock_off(comp_node);
+ mtk_mdp_comp_power_off(comp_node);
+
+ /*
+ * The master / rdma0 component will have pm_runtime_put called
+ * on it through mtk_mdp_m2m_stop_streaming, making it unnecessary to
+ * have mtk_mdp_comp_power_off called on it.
+ */
+ mtk_mdp_comp_clock_off(&mdp->comp_self);
}

static void mtk_mdp_wdt_worker(struct work_struct *work)
@@ -101,8 +115,6 @@ static int mtk_mdp_master_bind(struct device *dev)
int status;
struct mtk_mdp_dev *mdp = dev_get_drvdata(dev);

- mtk_mdp_register_component(mdp, &mdp->comp_self);
-
status = component_bind_all(dev, mdp);
if (status) {
dev_err(dev, "Failed to bind all components: %d\n", status);
@@ -124,8 +136,6 @@ static int mtk_mdp_master_bind(struct device *dev)
component_unbind_all(dev, mdp);

err_component_bind_all:
- mtk_mdp_unregister_component(mdp, &mdp->comp_self);
-
return status;
}

@@ -136,7 +146,6 @@ static void mtk_mdp_master_unbind(struct device *dev)
pm_runtime_disable(dev);
mtk_mdp_unregister_m2m_device(mdp);
component_unbind_all(dev, mdp);
- mtk_mdp_unregister_component(mdp, &mdp->comp_self);
}

static const struct component_master_ops mtk_mdp_com_ops = {
--
2.31.1.498.g6c1eba8ee3d-goog