On Mon, 2021-08-02 at 20:12 +0800, Eizan Miyamoto wrote:

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 <redacted>
---

Reviewed-by: Houlong Wei <houlong.wei@mediatek.com>

(no changes since v1)

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