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References: <20220429195350.85620-1-lyude@redhat.com>
In-Reply-To: <20220429195350.85620-1-lyude@redhat.com>
From:   Karol Herbst <kherbst@redhat.com>
Date:   Tue, 3 May 2022 21:23:30 +0200
Message-ID: <CACO55ttsBxe6V88CTtGZgUj8k+gT+ne+FD_9FD_OxowF1XG5Bg@mail.gmail.com>
Subject: Re: [PATCH] drm/nouveau/subdev/bus: Ratelimit logging for fault errors
To:     Lyude Paul <lyude@redhat.com>
Cc:     nouveau <nouveau@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        open list <linux-kernel@vger.kernel.org>
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not able to hit any error on my machine, but regardless:

Reviewed-by: Karol Herbst <kherbst@redhat.com>

I suspect there are more places where we could put it, but we can add
those later.

Anyway, I think it's valuable to push it through fixes, not sure how
far back we want to CC stable though.

On Fri, Apr 29, 2022 at 9:54 PM Lyude Paul <lyude@redhat.com> wrote:
>
> There's plenty of ways to fudge the GPU when developing on nouveau by
> mistake, some of which can result in nouveau seriously spamming dmesg with
> fault errors. This can be somewhat annoying, as it can quickly overrun the
> message buffer (or your terminal emulator's buffer) and get rid of actually
> useful feedback from the driver. While working on my new atomic only MST
> branch, I ran into this issue a couple of times.
>
> So, let's fix this by adding nvkm_error_ratelimited(), and using it to
> ratelimit errors from faults. This should be fine for developers, since
> it's nearly always only the first few faults that we care about seeing.
> Plus, you can turn off rate limiting in the kernel if you really need to.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> ---
>  drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h |  2 ++
>  drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c    | 14 +++++++-------
>  drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c     |  6 +++---
>  drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c     |  6 +++---
>  4 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h b/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> index 1665738948fb..96113c8bee8c 100644
> --- a/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> +++ b/drivers/gpu/drm/nouveau/include/nvkm/core/subdev.h
> @@ -62,4 +62,6 @@ void nvkm_subdev_intr(struct nvkm_subdev *);
>  #define nvkm_debug(s,f,a...) nvkm_printk((s), DEBUG,   info, f, ##a)
>  #define nvkm_trace(s,f,a...) nvkm_printk((s), TRACE,   info, f, ##a)
>  #define nvkm_spam(s,f,a...)  nvkm_printk((s),  SPAM,    dbg, f, ##a)
> +
> +#define nvkm_error_ratelimited(s,f,a...) nvkm_printk((s), ERROR, err_ratelimited, f, ##a)
>  #endif
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> index 53a6651ac225..80b5aaceeaad 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/gf100.c
> @@ -35,13 +35,13 @@ gf100_bus_intr(struct nvkm_bus *bus)
>                 u32 addr = nvkm_rd32(device, 0x009084);
>                 u32 data = nvkm_rd32(device, 0x009088);
>
> -               nvkm_error(subdev,
> -                          "MMIO %s of %08x FAULT at %06x [ %s%s%s]\n",
> -                          (addr & 0x00000002) ? "write" : "read", data,
> -                          (addr & 0x00fffffc),
> -                          (stat & 0x00000002) ? "!ENGINE " : "",
> -                          (stat & 0x00000004) ? "PRIVRING " : "",
> -                          (stat & 0x00000008) ? "TIMEOUT " : "");
> +               nvkm_error_ratelimited(subdev,
> +                                      "MMIO %s of %08x FAULT at %06x [ %s%s%s]\n",
> +                                      (addr & 0x00000002) ? "write" : "read", data,
> +                                      (addr & 0x00fffffc),
> +                                      (stat & 0x00000002) ? "!ENGINE " : "",
> +                                      (stat & 0x00000004) ? "PRIVRING " : "",
> +                                      (stat & 0x00000008) ? "TIMEOUT " : "");
>
>                 nvkm_wr32(device, 0x009084, 0x00000000);
>                 nvkm_wr32(device, 0x001100, (stat & 0x0000000e));
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> index ad8da523bb22..c75e463f3501 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv31.c
> @@ -45,9 +45,9 @@ nv31_bus_intr(struct nvkm_bus *bus)
>                 u32 addr = nvkm_rd32(device, 0x009084);
>                 u32 data = nvkm_rd32(device, 0x009088);
>
> -               nvkm_error(subdev, "MMIO %s of %08x FAULT at %06x\n",
> -                          (addr & 0x00000002) ? "write" : "read", data,
> -                          (addr & 0x00fffffc));
> +               nvkm_error_ratelimited(subdev, "MMIO %s of %08x FAULT at %06x\n",
> +                                      (addr & 0x00000002) ? "write" : "read", data,
> +                                      (addr & 0x00fffffc));
>
>                 stat &= ~0x00000008;
>                 nvkm_wr32(device, 0x001100, 0x00000008);
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> index 3a1e45adeedc..2055d0b100d3 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bus/nv50.c
> @@ -60,9 +60,9 @@ nv50_bus_intr(struct nvkm_bus *bus)
>                 u32 addr = nvkm_rd32(device, 0x009084);
>                 u32 data = nvkm_rd32(device, 0x009088);
>
> -               nvkm_error(subdev, "MMIO %s of %08x FAULT at %06x\n",
> -                          (addr & 0x00000002) ? "write" : "read", data,
> -                          (addr & 0x00fffffc));
> +               nvkm_error_ratelimited(subdev, "MMIO %s of %08x FAULT at %06x\n",
> +                                      (addr & 0x00000002) ? "write" : "read", data,
> +                                      (addr & 0x00fffffc));
>
>                 stat &= ~0x00000008;
>                 nvkm_wr32(device, 0x001100, 0x00000008);
> --
> 2.35.1
>