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SubjectRe: [PATCH v7 2/2] drm: add kms driver for loongson display controller
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Am 15.03.23 um 22:15 schrieb Sui Jingfeng:
> From: suijingfeng <suijingfeng@loongson.cn>
>
> Loongson display controller IP has been integrated in both Loongson
> North Bridge chipset(ls7a1000 and ls7a2000) and Loongson SoCs(ls2k1000
> and ls2k2000 etc), it even has been included in Loongson BMC products.
>
> This display controller is a PCI device, it has two display pipe. For
> the DC in LS7A1000 and LS2K1000 each way has a DVO output interface
> which provide RGB888 signals, vertical & horizontal synchronisations,
> and the pixel clock. Each CRTC is able to support 1920x1080@60Hz,
> the maximum resolution is 2048x2048 according to the hardware spec.
>
> For the DC in LS7A2000, each display pipe is equipped with a built-in
> HDMI encoder which is compliant with HDMI 1.4 specification, thus it
> support 3840x2160@30Hz. The first display pipe is also equipped with
> a transparent vga encoder which is parallel with the HDMI encoder.
> The DC in LS7A2000 is more complete, besides above feature, it has
> two hardware cursors, two hardware vblank counter and two scanout
> position recorders.
>
> v1 -> v2:
> 1) Use hpd status reg when polling for ls7a2000
> 2) Fix all warnings emerged when compile with W=1
>
> v2 -> v3:
> 1) Add COMPILE_TEST in Kconfig and make the driver off by default
> 2) Alphabetical sorting headers (Thomas)
> 3) Untangle register access functions as much as possible (Thomas)
> 4) Switch to TTM based memory manager and prefer cached mapping
> for Loongson SoC (Thomas)
> 5) Add chip id detection method, now all models are distinguishable.
> 6) Revise builtin HDMI phy driver, nearly all main stream mode
> below 4K@30Hz is tested, this driver supported these mode very
> well including clone display mode and extend display mode.
>
> v3 -> v4:
> 1) Quickly fix a small mistake.
>
> v4 -> v5:
> 1) Drop potential support for Loongson 2K series SoC temporary,
> this part should be resend with the DT binding patch in the future.
> 2) Add per display pipe debugfs support to the builtin HDMI encoder.
> 3) Rewrite atomic_update() for hardware cursors plane(Thomas)
> 4) Rewrite encoder and connector initialization part, untangle it
> according to the chip(Thomas).
>
> v5 -> v6:
> 1) Remove stray code which didn't get used, say lsdc_of_get_reserved_ram
> 2) Fix all typos I could found, make sentences and code more readable
> 3) Untange lsdc_hdmi*_connector_detect() function according to the pipe
> 4) After a serious consideration, we rename this driver as loongson.
> Because we also have drivers toward the LoongGPU IP in LS7A2000 and
> LS2K2000. Besides, there are also drivers about the external encoder,
> HDMI audio driver and vbios support etc. This patch only provide DC
> driver part, my teammate Li Yi believe that loongson will be more
> suitable for loongson graphics than lsdc in the long run.
>
> loongson.ko = LSDC + LoongGPU + encoders driver + vbios/DT ...
>
> v6 -> v7:
> 1) Add prime support, self-sharing is works. sharing buffer with etnaviv
> is also tested, and its works with limitation.
> 2) Implement buffer objects tracking with list_head.
> 3) S3(sleep to RAM) is tested on ls3a5000+ls7a2000 evb and it works.
> 4) Rewrite lsdc_bo_move, since ttm core stop allocating resources
> during BO creation. Patch V1 ~ V6 of this series no longer works
> on latest kernel. Thus, we send V7.
>
> Signed-off-by: Li Yi <liyi@loongson.cn>
> Signed-off-by: suijingfeng <suijingfeng@loongson.cn>
> Signed-off-by: Sui Jingfeng <15330273260@189.cn>

[SNIP]

> +u64 lsdc_bo_gpu_offset(struct ttm_buffer_object *tbo)
> +{
> + struct drm_device *ddev = tbo->base.dev;
> + struct ttm_resource *resource = tbo->resource;
> +
> + if (drm_WARN_ON(ddev, !tbo->pin_count))
> + return -ENODEV;

Returning -ENODEV when the function return value is unsigned doesn't
make much sense. I would also use 0 here.

Apart from that I briefly skimmed over the prime and TTM handling and
couldn't find anything obviously wrong.

I obviously can't review the hw specific stuff, but over all looks
pretty good to me.

Regards,
Christian.

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