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Message-ID: <f0e1c897b41706f15b765f1cbdf822dac5f596ef.camel@ndufresne.ca>
Date: Tue, 30 Sep 2025 14:00:35 -0400
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Himanshu Dewangan <h.dewangan@...sung.com>, mchehab@...nel.org,
robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
sumit.semwal@...aro.org, christian.koenig@....com,
alim.akhtar@...sung.com, manjun@...sung.com, nagaraju.s@...sung.com,
ih0206.lee@...sung.com, jehyung.lee@...sung.com
Cc: linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 00/29] media: codec: add new Samsung Exynos-MFC driver
Hi Himanshu,
Le mardi 30 septembre 2025 à 09:33 +0530, Himanshu Dewangan a écrit :
> Exynos MFC new driver upstream proposal
> +++++++++++++++++++++++++++++++++++++++
>
> The s5p-mfc driver in the kernel is quite outdated and has not kept up with the hardware advances of the MFC IP.
> Going forward, we want to provide support for all the later versions of MFC in open source (both mobile and
> ExynosAuto would be supported by Samsung)
>
> We (Samsung) would like to propose a new driver for the latest generation of Samsung MFC (Multi-Format Codec) hardware.
> Although the kernel already contains a Samsung MFC driver (drivers/media/platform/s5p-mfc/), the newer hardware
> diverges significantly from the previous generations, in features supported, register interface and in system integration.
> This has necessitated a new driver, rather than updating the existing one.
I wont deny that sometimes a new driver is needed, and I encourage you to defend
your point. It does just justify any form of copy paste, also understand that
device descriptions should be independent from the driver implementation. This
is also why this is reviewed indecently, and DT nack won't ever be ignored by
us.
From quick walk through, I'm not convince this new driver actually makes use of
everything new in Linux and Linux Media since 2011. It will be important for you
to research what other modern drivers do, and what could apply to your code
base. I'm quite skeptical with all the custom memory handling code, which
generally indicates the miss-use of dma APIs. Realistically, you will have to
split your driver in smaller parts and submit in a way we can see your design
principle, and not just randomly unused files being added. Considering the state
of it, we are up to 20 or 30 revision, with 29 patches, you won't get to the end
of that process.
V4L2 wise, one of the common mistakes is that you are adding a lot of new
controls, most of them just slammed as vendor control without even trying to
generalize. It did make sense in 2011, since there was no decoder to compare
against, but today there is a lot of example and overlap between various brand.
Omitting documentation and not keeping the API addition separate is also a no go
for me. Make it very clear whenever something that will live in our API forever
is to be added.
We also added rules since 2011 that enforce drivers submitter to show that
proper testing have occurred. Its starts with the very basic v4l2-compliance
report which you have omitted. Since its codec driver, we require a summary of
your conformance decoding testing done with fluster[] with the supported
framework of your choice (for v4l2 stateful, ffmpeg and gstreamer are supported,
you can add more, as long as they are open source).
We also expect that your firmware has been submitted to linux-firmware with a
link to that submission. Without that, we can only consider your set as an RFC
to show people what is coming.
regards,
Nicolas
>
>
> Current driver vs targetted driver comparison
> +++++++++++++++++++++++++++++++++++++++++++++
>
> Target Feature
> Current mainline : Simple V4L2/ VB2 interface based encoder/ decoder
> New proposed driver: Dual core support, NAL-q support, LLC, Coredump, performance
> measurement, plugin driver architecture, hardware manager(meerkat), DRM/OTF,
> Resource manager, bandwidth compression, New Pixel formats (NV12N, YV12, P010,
> SBWC, RGB family), 10 bit support, HDR support, Prio and RR Process Scheduler support,
>
> Register map
> Current mainline : Fixed register layout, compatible across s5p variants
> New proposed driver: Completely redesigned register set, incompatible with old layout
>
> Command model
> Current mainline : Mailbox-style command queue
> New proposed driver: Ring-buffer command queue with different signaling
>
> Memory management
> Current mainline : CMA-backed contiguous buffers, ION legacy
> New proposed driver: dma-heap / scatter-gather buffers with strict alignment rules
>
> Firmware
> Current mainline : Supports up to Firmware v12, Legacy binary format, loaded via shared mechanism
> New proposed driver: New firmware format, different protocol for control messages. Support Firmware v13 onwards
>
> DT bindings
> Current mainline : Single clock + reset, simple PM
> New proposed driver: Multiple clocks, reset domains, runtime PM dependencies
>
> Error handling
> Current mainline : Simple IRQ error flags
> New proposed driver: Detailed error codes, recovery sequences required
>
> Code impact
> Current mainline :~8k LOC, minimal conditionals
> New proposed driver: ~65KLOC with full features
>
>
> Plan for supporting latest MFC (Best balance between code clarity and long-term kernel health, while still respecting ABI and legacy users.)
> 1 We propose a new driver (exynos-mfc) for the latest generation of Samsung MFC (Multi-Format Codec) hardware.
> 2 MFC FW V6 to V12 will be supported by existing mainline (s5p-mfc) and later versions by Exynos-mfc driver
> 3 The existing MFC driver will remain available for older SoC’s and will not be broken. The new driver will only bind
> to new compatible strings in DT, avoiding regressions for legacy hardware. Samsung will take responsibility for
> maintaining both drivers until the old one can be formally marked as “legacy.”
> 4 Keep it buildable for old SoCs but clearly say new SoCs should use the new driver.
> 5 VIDEO_SAMSUNG_S5P_MFC and VIDEO_EXYNOS_MFC will both be supported for an agreed time
> 6 Long term Support for new driver - commitment from Samsung
> 7 The hardware has diverged to the point where conditionally supporting both in one codebase is worse for long-term kernel health
> 8 Splitting keeps the code clean, testable, and reviewable, while ensuring legacy users aren’t broken due to user space ABI guarantees.
> This seems more clean and easier approach Both can coexist without code spaghetti.
>
> Features and description supported
> ++++++++++++++++++++++++++++++++++
>
> 1 MFC driver registration Probe functionality and video nodes registration
> 2 MFC driver open & close support MFC firmware loading, "ls" & "cat" on the video nodes and udev rules on the video nodes
> 3 H264 decoding H264 decoding support - HW supported profiles & levels (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 4 HEVC decoding HEVC decoding support - HW supported profiles & levels (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 5 VP8 decoding VP8 decoding support - HW supported profiles & levels (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 6 VP9 decoding VP9 decoding support - HW supported profiles & levels (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 7 AV1 decoding AV1 decoding support - HW supported profiles & levels (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 8 H264 encoding H264 encoding support - Basic encoding (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 9 HEVC encoding HEVC encoding support - Basic encoding (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 10 VP8 encoding VP8 encoding support - Basic encoding (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 11 VP9 encoding VP9 encoding support - Basic encoding (YUV420 Semi-Planar, 8-bit, min/max resolution)
> 12 Debug fs support Debug fs to control the MFC functionalities
> 13 Debug log support Debug logs to get on the dmesg prompt for debug purpose
> 14 Debug SFR dump support MFC SFR dumps during failures
> 15 NAL Queue mode control NAL Queue mode support
> 16 Batch mode control Batch mode support
> 17 HW supported YUV formats YUV 420, 422, 444 (planar, semi-planar) formats support as per MFC HW specification
> 18 HW supported RGB formats RGB format support as per MFC HW specification
> 19 Multi instance decoding/encoding Multi instance decoding/encoding
> 20 Suspend and resume Suspend and resume support
> 21 Runtime suspend and resume Runtime suspend and resume support
> 22 Priority decoding (decoders) Priority decoding support
> 23 Frame delay configuration (decoders) Frame delay configuration support
> 24 Error handling and conceal control (decoders) HW/Platform limitations should be gracefully exited and,
> bit stream errors should be reported or concealed with warning indication
> 25 Reference frame control (encoders) Reference frame control support
> 26 SPS/PPS control (encoders) SPS/PPS control support
> 27 Loop filter control (encoders) Loop filter control support
> 28 B frame support (encoders) B frame support
> 29 GOP control (encoders) GOP control support
> 30 Frame rate control (encoders) Frame rate control support
>
> Features to be supported in 2026
> +++++++++++++++++++++++++++++++++
>
> 31 Bit rate control (encoders) Bit rate control support
> 32 QP control (encoders) QP control support
> 33 I/IDR control (encoders) I/IDR control support
> 34 Scalable control (encoders) Scalable control support
> 35 ROI control (encoders) ROI control support
> 36 Multi slice control (encoders) Multi slice control support
> 37 Profile/Level control (encoders) Profile/Level control support
> 38 Padding control (encoders) Padding control support
> 39 Aspect ratio control (encoders) Aspect ratio control support
> 40 Buffer full handling (encoders) Buffer full handling support
> 41 SBWC SBWC bandwidth compression support
> 42 10-bit support 10-bit support as per MFC HW specification
> 43 Secure signed FW support Security signed FW support
> 44 Secure playback DRM content playback for decoders
> 45 HDR Support (decoders) HDR metadata support
> 46 Dynamic resolution change Dynamic resolution change support
>
> Nagaraju Siddineni (29):
> dt-bindings: media: mfc: Add Exynos MFC devicetree binding
> arm64: dts: mfc: Add MFC device tree for Auto V920 SoC
> media: mfc: Add MFC driver data structures and debugging macros
> media: mfc: Add full register map and bit definitions for MFC hardware
> media: mfc: Add MFC driver header files and core utilities
> media: mfc: Add MFC core hardware register and debugfs APIs
> media: mfc: Add MFC core command, hwlock, ISR and run functionalities
> media: mfc: Add Exynos‑MFC driver probe support
> media: mfc: Add bus‑devfreq, QoS, multi‑view and control
> infrastructure
> media: mfc: Add buffer‑queue and IOVMM support
> media: mfc: Add rate‑calculation framework and memory utilities
> media: mfc: Introduce QoS support and instance context handling
> media: mfc: Add decoder core sync functions
> media: mfc: Add buffer‑control framework
> media: mfc: Add decoder resource‑management (RM) support and
> load‑balancing
> media: mfc: Enhance HW‑lock handling, scheduling and error recovery
> media: mfc: Add VB2 decoder support
> media: mfc: Add V4L2 decoder driver
> media: mfc: Add QoS, Butler workqueue, and priority‑based scheduling
> media: mfc: Add H264 decoder support
> media: mfc: Add multi‑codec support & QoS improvements
> media: mfc: Add H.264 encoder support with buffer and QoS improvements
> media: mfc: Add encoder parameters, ROI & QoS support
> media: mfc: Add encoder VB2 support to driver
> media: mfc: Add encoder v4l2 driver interface
> media: mfc: Add full encoder support
> media: mfc: Add H.264 encoder support
> media: mfc: Add AVC, VP8, VP9, and HEVC encoding support
> media: mfc: Hardware‑accelerated encoding support
>
> .../bindings/media/samsung,exynos-mfc.yaml | 77 +
> MAINTAINERS | 10 +
> .../dts/exynos/exynosautov920-evt2-mfc.dtsi | 630 +++
> .../arm64/boot/dts/exynos/exynosautov920.dtsi | 1 +
> drivers/media/platform/samsung/Kconfig | 7 +
> drivers/media/platform/samsung/Makefile | 1 +
> .../media/platform/samsung/exynos-mfc/Kconfig | 34 +
> .../platform/samsung/exynos-mfc/Makefile | 26 +
> .../samsung/exynos-mfc/base/mfc_buf.c | 765 +++
> .../samsung/exynos-mfc/base/mfc_buf.h | 43 +
> .../samsung/exynos-mfc/base/mfc_common.h | 444 ++
> .../samsung/exynos-mfc/base/mfc_data_struct.h | 2014 +++++++
> .../samsung/exynos-mfc/base/mfc_debug.h | 247 +
> .../samsung/exynos-mfc/base/mfc_format.h | 316 ++
> .../samsung/exynos-mfc/base/mfc_macros.h | 95 +
> .../samsung/exynos-mfc/base/mfc_media.h | 554 ++
> .../samsung/exynos-mfc/base/mfc_mem.c | 995 ++++
> .../samsung/exynos-mfc/base/mfc_mem.h | 155 +
> .../samsung/exynos-mfc/base/mfc_qos.c | 1070 ++++
> .../samsung/exynos-mfc/base/mfc_qos.h | 99 +
> .../samsung/exynos-mfc/base/mfc_queue.c | 966 ++++
> .../samsung/exynos-mfc/base/mfc_queue.h | 158 +
> .../exynos-mfc/base/mfc_rate_calculate.c | 640 +++
> .../exynos-mfc/base/mfc_rate_calculate.h | 106 +
> .../samsung/exynos-mfc/base/mfc_regs.h | 58 +
> .../samsung/exynos-mfc/base/mfc_regs_mfc.h | 1002 ++++
> .../samsung/exynos-mfc/base/mfc_sched.h | 30 +
> .../samsung/exynos-mfc/base/mfc_utils.c | 401 ++
> .../samsung/exynos-mfc/base/mfc_utils.h | 481 ++
> .../media/platform/samsung/exynos-mfc/mfc.c | 1366 +++++
> .../platform/samsung/exynos-mfc/mfc_core.c | 703 +++
> .../samsung/exynos-mfc/mfc_core_buf_ctrl.c | 543 ++
> .../samsung/exynos-mfc/mfc_core_cmd.c | 576 ++
> .../samsung/exynos-mfc/mfc_core_cmd.h | 41 +
> .../samsung/exynos-mfc/mfc_core_enc_param.c | 1463 ++++++
> .../samsung/exynos-mfc/mfc_core_enc_param.h | 23 +
> .../samsung/exynos-mfc/mfc_core_hw_reg_api.c | 122 +
> .../samsung/exynos-mfc/mfc_core_hw_reg_api.h | 144 +
> .../samsung/exynos-mfc/mfc_core_hwlock.c | 761 +++
> .../samsung/exynos-mfc/mfc_core_hwlock.h | 80 +
> .../samsung/exynos-mfc/mfc_core_intlock.c | 98 +
> .../samsung/exynos-mfc/mfc_core_intlock.h | 20 +
> .../samsung/exynos-mfc/mfc_core_isr.c | 2104 ++++++++
> .../samsung/exynos-mfc/mfc_core_isr.h | 25 +
> .../samsung/exynos-mfc/mfc_core_ops.c | 813 +++
> .../samsung/exynos-mfc/mfc_core_ops.h | 16 +
> .../platform/samsung/exynos-mfc/mfc_core_pm.c | 209 +
> .../platform/samsung/exynos-mfc/mfc_core_pm.h | 33 +
> .../samsung/exynos-mfc/mfc_core_reg_api.c | 597 +++
> .../samsung/exynos-mfc/mfc_core_reg_api.h | 380 ++
> .../samsung/exynos-mfc/mfc_core_run.c | 541 ++
> .../samsung/exynos-mfc/mfc_core_run.h | 35 +
> .../samsung/exynos-mfc/mfc_core_sched_prio.c | 431 ++
> .../samsung/exynos-mfc/mfc_core_sync.c | 423 ++
> .../samsung/exynos-mfc/mfc_core_sync.h | 34 +
> .../samsung/exynos-mfc/mfc_ctx_ctrl.c | 1469 ++++++
> .../platform/samsung/exynos-mfc/mfc_debugfs.c | 248 +
> .../platform/samsung/exynos-mfc/mfc_debugfs.h | 20 +
> .../samsung/exynos-mfc/mfc_dec_v4l2.c | 1739 +++++++
> .../samsung/exynos-mfc/mfc_dec_v4l2.h | 20 +
> .../platform/samsung/exynos-mfc/mfc_dec_vb2.c | 394 ++
> .../platform/samsung/exynos-mfc/mfc_dec_vb2.h | 19 +
> .../samsung/exynos-mfc/mfc_enc_v4l2.c | 4614 +++++++++++++++++
> .../samsung/exynos-mfc/mfc_enc_v4l2.h | 20 +
> .../platform/samsung/exynos-mfc/mfc_enc_vb2.c | 443 ++
> .../platform/samsung/exynos-mfc/mfc_enc_vb2.h | 19 +
> .../platform/samsung/exynos-mfc/mfc_rm.c | 2652 ++++++++++
> .../platform/samsung/exynos-mfc/mfc_rm.h | 110 +
> 68 files changed, 34773 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/media/samsung,exynos-mfc.yaml
> create mode 100644 arch/arm64/boot/dts/exynos/exynosautov920-evt2-mfc.dtsi
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/Kconfig
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/Makefile
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_buf.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_buf.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_common.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_data_struct.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_debug.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_format.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_macros.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_media.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_mem.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_mem.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_qos.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_qos.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_queue.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_queue.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_rate_calculate.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_rate_calculate.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_regs.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_regs_mfc.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_sched.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_utils.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/base/mfc_utils.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_buf_ctrl.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_cmd.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_cmd.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_enc_param.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_enc_param.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_hw_reg_api.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_hw_reg_api.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_hwlock.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_hwlock.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_intlock.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_intlock.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_isr.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_isr.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_ops.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_ops.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_pm.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_pm.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_reg_api.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_reg_api.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_run.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_run.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_sched_prio.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_sync.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_core_sync.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_ctx_ctrl.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_debugfs.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_debugfs.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_dec_v4l2.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_dec_v4l2.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_dec_vb2.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_dec_vb2.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_enc_v4l2.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_enc_v4l2.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_enc_vb2.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_enc_vb2.h
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_rm.c
> create mode 100644 drivers/media/platform/samsung/exynos-mfc/mfc_rm.h
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