Re: [RFC] media: renesas: vsp1: Add VSPD underrun detection & tracing

[Eugeniu Rosca <erosca@de.adit-jv.com>]

On Di, Apr 26, 2022 at 10:37:07 +0200, Eugeniu Rosca wrote:
> A barely noticeable (especially if hardly reproducible) display flicker
> may not be the biggest concern in the development environment. However,
> an automotive OEM will not only notice it, but will also be haunted by
> its phenomenon/nature till it is understood in the greatest detail and
> ultimately eradicated, to avoid impairing user experience.
> 
> Troubleshooting the above without the right tools becomes a nightmare.
> 
> Since VSPD underruns may indeed cause [1] display flicker, we believe
> that having a minimal/lightweight support for detecting and logging
> such events would be extremely beneficial. Obviously, this only applies
> to VSP2 modules having an interface to DU (i.e. not mem2mem).
> 
> This implementation is heavily inspired by Koji Matsuoka's work [2-3],
> but has been refactored to hopefully become production/mainline-friendly
> (the original feature is intended for the development environment only).
> 
> [1] https://lore.kernel.org/linux-renesas-soc/20220421161259.GA2660@lxhi-065
> [2] https://github.com/renesas-rcar/linux-bsp/commit/3469001c3098
>     ("v4l: vsp1: Add underrun hung-up workaround")
> [3] https://github.com/renesas-rcar/linux-bsp/commit/12ea79975a10
>     ("v4l: vsp1: Add underrun debug messege option")
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Kieran Bingham <kieran.bingham@ideasonboard.com>
> Cc: Koji Matsuoka <koji.matsuoka.xm@renesas.com>

Superseded by https://lore.kernel.org/linux-renesas-soc/1651584010-10156-1-git-send-email-erosca@de.adit-jv.com

Best regards,
Eugeniu