[PATCH v8 16/23] drm/mediatek: mtk_hdmi: Split driver and add common probe function

[AngeloGioacchino Del Regno]

Il 11/04/25 10:18, CK Hu (胡俊光) ha scritto:
> On Wed, 2025-04-09 at 15:13 +0200, AngeloGioacchino Del Regno wrote:
>> External email : Please do not click links or open attachments until you have verified the sender or the content.
>>
>>
>> In preparation for adding a new driver for the HDMI TX v2 IP,
>> split out the functions that will be common between the already
>> present mtk_hdmi (v1) driver and the new one.
>>
>> Since the probe flow for both drivers is 90% similar, add a common
>> probe function that will be called from each driver's .probe()
>> callback, avoiding lots of code duplication.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
>> ---
>>   drivers/gpu/drm/mediatek/Kconfig           |  11 +-
>>   drivers/gpu/drm/mediatek/Makefile          |   1 +
>>   drivers/gpu/drm/mediatek/mtk_hdmi.c        | 542 +--------------------
>>   drivers/gpu/drm/mediatek/mtk_hdmi_common.c | 426 ++++++++++++++++
>>   drivers/gpu/drm/mediatek/mtk_hdmi_common.h | 188 +++++++
>>   5 files changed, 633 insertions(+), 535 deletions(-)
>>   create mode 100644 drivers/gpu/drm/mediatek/mtk_hdmi_common.c
>>   create mode 100644 drivers/gpu/drm/mediatek/mtk_hdmi_common.h
>>
>> diff --git a/drivers/gpu/drm/mediatek/Kconfig b/drivers/gpu/drm/mediatek/Kconfig
>> index e47debd60619..994b48b82d44 100644
>> --- a/drivers/gpu/drm/mediatek/Kconfig
>> +++ b/drivers/gpu/drm/mediatek/Kconfig
>> @@ -30,9 +30,18 @@ config DRM_MEDIATEK_DP
>>          help
>>            DRM/KMS Display Port driver for MediaTek SoCs.
>>
>> +config DRM_MEDIATEK_HDMI_COMMON
>> +       tristate
>> +       depends on DRM_MEDIATEK
>> +       select DRM_DISPLAY_HDMI_HELPER
>> +       select DRM_DISPLAY_HELPER
>> +       select SND_SOC_HDMI_CODEC if SND_SOC
>> +       help
>> +         MediaTek SoC HDMI common library
>> +
>>   config DRM_MEDIATEK_HDMI
>>          tristate "DRM HDMI Support for Mediatek SoCs"
>>          depends on DRM_MEDIATEK
>> -       select SND_SOC_HDMI_CODEC if SND_SOC
>> +       select DRM_MEDIATEK_HDMI_COMMON
>>          help
>>            DRM/KMS HDMI driver for Mediatek SoCs
>> diff --git a/drivers/gpu/drm/mediatek/Makefile b/drivers/gpu/drm/mediatek/Makefile
>> index 43afd0a26d14..78cf2d4fc85f 100644
>> --- a/drivers/gpu/drm/mediatek/Makefile
>> +++ b/drivers/gpu/drm/mediatek/Makefile
>> @@ -21,6 +21,7 @@ mediatek-drm-y := mtk_crtc.o \
>>
>>   obj-$(CONFIG_DRM_MEDIATEK) += mediatek-drm.o
>>
>> +obj-$(CONFIG_DRM_MEDIATEK_HDMI_COMMON) += mtk_hdmi_common.o
> 
> The whole patch looks good to me.
> But make common part to a module looks a little bit more modularized.
> Let things to be simple, I would like the whole MediaTek hdmi driver be a single module.
> For MediaTek drm driver, it is already broken to mediatek-drm, hdmi, dp modules.
> Maybe someday dsi or dpi would be broken to modules.
> So I would like hdmi to be a single module which include v1, v2 and common part.
> If someday we need to optimize code size, then send patch to break hdmi module.
> 

Hello CK,

The HDMIv1 and HDMIv2 drivers are handling two *very* different IPs that can never
be *both* present at the same time on one SoC: having one Kconfig for both would
not only add unnecessary bloat (especially on older SoCs!!), but would actually be
wrong.

Also, please be aware that old LK bootloaders (smartphones/tablets) have a very
limited RAM carveout for kernel + ramdisk that should be around 8MB if I recall
correctly.

Remember as well that these devices *cannot* run different bootloaders as those
are only able to run *OEM signed* binaries in the early bootchain, so replacing
the bootloader is not a viable solution.

It's true, people can (and most probably want to and will) build this as a module
but, in my opinion, freedom should be given to have the HDMI driver built-in even
in these cases - and that's another good reason to keep them split.

This is done to avoid being hostile to old platforms, in full upstream spirit.

Regards,
Angelo

> Regards,
> CK
> 
>>   obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_cec.o
>>   obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_hdmi.o
>>   obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_hdmi_ddc.o
>> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
>