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SubjectRe: [PATCH v7 0/6] Exynos: Simple QoS for exynos-bus using interconnect
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Hi Sylwester,

When I tested this patchset on Odroid-U3,
After setting 0 bps by interconnect[1][2],
the frequency of devfreq devs sustain the high frequency
according to the pm qos request.

So, I try to find the cause of this situation.
In result, it seems that interconnect exynos driver
updates the pm qos request to devfreq device
during the kernel booting. Do you know why the exynos
interconnect driver request the pm qos during probe
without the mixer request?

PS. The passive governor has a bug related to PM_QOS interface.
So, I posted the patch[4].


[1] interconnect_graph
root@localhost:~# cat /sys/kernel/debug/interconnect/interconnect_graph
digraph {
rankdir = LR
node [shape = record]
subgraph cluster_1 {
label = "soc:bus_dmc"
"2:bus_dmc" [label="2:bus_dmc
|avg_bw=0kBps
|peak_bw=0kBps"]
}
subgraph cluster_2 {
label = "soc:bus_leftbus"
"3:bus_leftbus" [label="3:bus_leftbus
|avg_bw=0kBps
|peak_bw=0kBps"]
}
subgraph cluster_3 {
label = "soc:bus_display"
"4:bus_display" [label="4:bus_display
|avg_bw=0kBps
|peak_bw=0kBps"]
}
"3:bus_leftbus" -> "2:bus_dmc"
"4:bus_display" -> "3:bus_leftbus"


[2] interconnect_summary
root@localhost:~# cat /sys/kernel/debug/interconnect/interconnect_summary
node tag avg peak
--------------------------------------------------------------------
bus_dmc 0 0
12c10000.mixer 0 0 0
bus_leftbus 0 0
12c10000.mixer 0 0 0
bus_display 0 0
12c10000.mixer 0 0 0


[3] devfreq_summary
root@localhost:~# cat /sys/kernel/debug/devfreq/devfreq_summary
dev parent_dev governor timer polling_ms cur_freq_Hz min_freq_Hz max_freq_Hz
------------------------------ ------------------------------ --------------- ---------- ---------- ------------ ------------ ------------
soc:bus_dmc null simple_ondemand deferrable 50 400000000 400000000 400000000
soc:bus_acp soc:bus_dmc passive null 0 267000000 100000000 267000000
soc:bus_c2c soc:bus_dmc passive null 0 400000000 100000000 400000000
soc:bus_leftbus null simple_ondemand deferrable 50 200000000 200000000 200000000
soc:bus_rightbus soc:bus_leftbus passive null 0 200000000 100000000 200000000
soc:bus_display soc:bus_leftbus passive null 0 200000000 200000000 200000000
soc:bus_fsys soc:bus_leftbus passive null 0 134000000 100000000 134000000
soc:bus_peri soc:bus_leftbus passive null 0 100000000 50000000 100000000
soc:bus_mfc soc:bus_leftbus passive null 0 200000000 100000000 200000000


[4] PM / devfreq: passive: Update frequency when start governor
https://patchwork.kernel.org/project/linux-pm/patch/20201103070646.18687-1-cw00.choi@samsung.com/


On 10/30/20 9:51 PM, Sylwester Nawrocki wrote:
>
> This patchset adds interconnect API support for the Exynos SoC "samsung,
> exynos-bus" compatible devices, which already have their corresponding
> exynos-bus driver in the devfreq subsystem. Complementing the devfreq
> driver with an interconnect functionality allows to ensure the QoS
> requirements of devices accessing the system memory (e.g. video processing
> devices) are fulfilled and aallows to avoid issues like the one discussed
> in thread [1].
>
> This patch series adds implementation of the interconnect provider per each
> "samsung,exynos-bus" compatible DT node, with one interconnect node per
> provider. The interconnect code which was previously added as a part of
> the devfreq driver has been converted to a separate platform driver.
> In the devfreq a corresponding virtual child platform device is registered.
> Integration of devfreq and interconnect frameworks is achieved through
> the PM QoS API.
>
> A sample interconnect consumer for exynos-mixer is added in patches 5/6,
> 6/6, it is currently added only for exynos4412 and allows to address the
> mixer DMA underrun error issues [1].
>
> Changes since v6:
> - the interconnect consumer DT bindings are now used to describe dependencies
> of the interconnects (samsung,exynos-bus nodes),
> - bus-width property replaced with samsung,data-clk-ratio,
> - adaptation to recent changes in the interconnect code
> (of_icc_get_from_provider(), icc_node_add()).
>
> The series has been tested on Odroid U3 board. It is based on v5.10-rc1.
>
> --
> Regards,
> Sylwester
>
>
> Changes since v5:
> - addition of "bus-width: DT property, which specifies data width
> of the interconnect bus (patches 1...2/6),
> - addition of synchronization of the interconnect bandwidth setting
> with VSYNC (patch 6/6).
>
> Changes since v3 [4] (v4 skipped to align with patchset [1]), detailed
> changes are listed in each patch:
> - conversion to a separate interconnect (platform) driver,
> - an update of the DT binding documenting new optional properties:
> #interconnect-cells, samsung,interconnect-parent in "samsung,exynos-bus"
> nodes,
> - new DT properties added to the SoC, rather than to the board specific
> files.
>
> Changes since v2 [5]:
> - Use icc_std_aggregate().
> - Implement a different modification of apply_constraints() in
> drivers/interconnect/core.c (patch 03).
> - Use 'exynos,interconnect-parent-node' in the DT instead of
> 'devfreq'/'parent', depending on the bus.
> - Rebase on DT patches that deprecate the 'devfreq' DT property.
> - Improve error handling, including freeing generated IDs on failure.
> - Remove exynos_bus_icc_connect() and add exynos_bus_icc_get_parent().
>
> Changes since v1 [6]:
> - Rebase on coupled regulators patches.
> - Use dev_pm_qos_*() API instead of overriding frequency in
> exynos_bus_target().
> - Use IDR for node ID allocation.
> - Reverse order of multiplication and division in
> mixer_set_memory_bandwidth() (patch 07) to avoid integer overflow.
>
>
> References:
> [1] https://patchwork.kernel.org/patch/10861757/ (original issue)
> [2] https://protect2.fireeye.com/v1/url?k=383efc40-67a5c559-383f770f-000babff3793-a505fcd0b7477e5e&q=1&e=ad8ffb9f-f90b-49a7-a3df-2ab066a8c4ee&u=https%3A%2F%2Fwww.spinics.net%2Flists%2Flinux-samsung-soc%2Fmsg70014.html
> [3] https://protect2.fireeye.com/v1/url?k=13f0c488-4c6bfd91-13f14fc7-000babff3793-98a59bf1c5c6f1fb&q=1&e=ad8ffb9f-f90b-49a7-a3df-2ab066a8c4ee&u=https%3A%2F%2Fwww.spinics.net%2Flists%2Farm-kernel%2Fmsg810722.html
> [4] https://lore.kernel.org/linux-pm/20191220115653.6487-1-a.swigon@samsung.com
> [5] https://patchwork.kernel.org/cover/11054417/ (v1 of this RFC)
> [6] https://patchwork.kernel.org/cover/11152595/ (v2 of this RFC)
>
>
> Artur Świgoń (1):
> ARM: dts: exynos: Add interconnects to Exynos4412 mixer
>
> Sylwester Nawrocki (5):
> dt-bindings: devfreq: Add documentation for the interconnect
> properties
> interconnect: Add generic interconnect driver for Exynos SoCs
> PM / devfreq: exynos-bus: Add registration of interconnect child
> device
> ARM: dts: exynos: Add interconnect properties to Exynos4412 bus nodes
> drm: exynos: mixer: Add interconnect support
>
> .../devicetree/bindings/devfreq/exynos-bus.txt | 68 ++++++-
> arch/arm/boot/dts/exynos4412.dtsi | 7 +
> drivers/devfreq/exynos-bus.c | 17 ++
> drivers/gpu/drm/exynos/exynos_mixer.c | 146 ++++++++++++++-
> drivers/interconnect/Kconfig | 1 +
> drivers/interconnect/Makefile | 1 +
> drivers/interconnect/exynos/Kconfig | 6 +
> drivers/interconnect/exynos/Makefile | 4 +
> drivers/interconnect/exynos/exynos.c | 198 +++++++++++++++++++++
> 9 files changed, 438 insertions(+), 10 deletions(-)
> create mode 100644 drivers/interconnect/exynos/Kconfig
> create mode 100644 drivers/interconnect/exynos/Makefile
> create mode 100644 drivers/interconnect/exynos/exynos.c
>
> --
> 2.7.4
>
>
>


--
Best Regards,
Chanwoo Choi
Samsung Electronics

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