linux-kernel - Re: [PATCH v1 3/6] drm/lima: set bus

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Message-ID: <CA+E=qVfjKvW=R6NaF7eEKkHk91HLGnohQjM8h-3Kh=fv61WgJA@mail.gmail.com>
Date: Wed, 17 Jan 2024 10:23:45 -0800
From: Vasily Khoruzhick <anarsoul@...il.com>
To: Erico Nunes <nunes.erico@...il.com>
Cc: Qiang Yu <yuq825@...il.com>, dri-devel@...ts.freedesktop.org, 
	lima@...ts.freedesktop.org, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Sumit Semwal <sumit.semwal@...aro.org>, christian.koenig@....com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/6] drm/lima: set bus_stop bit before hard reset

On Tue, Jan 16, 2024 at 7:12 PM Erico Nunes <nunes.erico@...il.com> wrote:
>
> This is required for reliable hard resets. Otherwise, doing a hard reset
> while a task is still running (such as a task which is being stopped by
> the drm_sched timeout handler) may result in random mmu write timeouts
> or lockups which cause the entire gpu to hang.

It looks like Mali driver is doing the same, so it totally makes sense.

> Signed-off-by: Erico Nunes <nunes.erico@...il.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@...il.com>

> ---
>  drivers/gpu/drm/lima/lima_pp.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/lima/lima_pp.c b/drivers/gpu/drm/lima/lima_pp.c
> index a8f8f63b8295..ac097dd75072 100644
> --- a/drivers/gpu/drm/lima/lima_pp.c
> +++ b/drivers/gpu/drm/lima/lima_pp.c
> @@ -168,6 +168,11 @@ static void lima_pp_write_frame(struct lima_ip *ip, u32 *frame, u32 *wb)
>         }
>  }
>
> +static int lima_pp_bus_stop_poll(struct lima_ip *ip)
> +{
> +       return !!(pp_read(LIMA_PP_STATUS) & LIMA_PP_STATUS_BUS_STOPPED);
> +}
> +
>  static int lima_pp_hard_reset_poll(struct lima_ip *ip)
>  {
>         pp_write(LIMA_PP_PERF_CNT_0_LIMIT, 0xC01A0000);
> @@ -181,6 +186,14 @@ static int lima_pp_hard_reset(struct lima_ip *ip)
>
>         pp_write(LIMA_PP_PERF_CNT_0_LIMIT, 0xC0FFE000);
>         pp_write(LIMA_PP_INT_MASK, 0);
> +
> +       pp_write(LIMA_PP_CTRL, LIMA_PP_CTRL_STOP_BUS);
> +       ret = lima_poll_timeout(ip, lima_pp_bus_stop_poll, 10, 100);
> +       if (ret) {
> +               dev_err(dev->dev, "pp %s bus stop timeout\n", lima_ip_name(ip));
> +               return ret;
> +       }
> +
>         pp_write(LIMA_PP_CTRL, LIMA_PP_CTRL_FORCE_RESET);
>         ret = lima_poll_timeout(ip, lima_pp_hard_reset_poll, 10, 100);
>         if (ret) {
> --
> 2.43.0
>