[PATCH 6/7] drm/tidss: Fix race condition while handling interrupt registers

[Jon Cormier]

On Mon, Oct 21, 2024 at 10:08 AM Tomi Valkeinen
<tomi.valkeinen at ideasonboard.com> wrote:
>
> From: Devarsh Thakkar <devarsht at ti.com>
>
> The driver has a spinlock for protecting the irq_masks field and irq
> enable registers. However, the driver misses protecting the irq status
> registers which can lead to races.
>
> Take the spinlock when accessing irqstatus too.
>
> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
> Cc: stable at vger.kernel.org
> Signed-off-by: Devarsh Thakkar <devarsht at ti.com>
> [Tomi: updated the desc]
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> ---
>  drivers/gpu/drm/tidss/tidss_dispc.c | 4 ++++
>  drivers/gpu/drm/tidss/tidss_irq.c   | 2 ++
>  2 files changed, 6 insertions(+)

Reviewed-by: Jonathan Cormier <jcormier at criticallink.com>
Tested an equivalent patch for several weeks.
Tested-by: Jonathan Cormier <jcormier at criticallink.com>

>
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 515f82e8a0a5..07f5c26cfa26 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -2767,8 +2767,12 @@ static void dispc_init_errata(struct dispc_device *dispc)
>   */
>  static void dispc_softreset_k2g(struct dispc_device *dispc)
>  {
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&dispc->tidss->wait_lock, flags);
>         dispc_set_irqenable(dispc, 0);
>         dispc_read_and_clear_irqstatus(dispc);
> +       spin_unlock_irqrestore(&dispc->tidss->wait_lock, flags);
>
>         for (unsigned int vp_idx = 0; vp_idx < dispc->feat->num_vps; ++vp_idx)
>                 VP_REG_FLD_MOD(dispc, vp_idx, DISPC_VP_CONTROL, 0, 0, 0);
> diff --git a/drivers/gpu/drm/tidss/tidss_irq.c b/drivers/gpu/drm/tidss/tidss_irq.c
> index 3cc4024ec7ff..8af4682ba56b 100644
> --- a/drivers/gpu/drm/tidss/tidss_irq.c
> +++ b/drivers/gpu/drm/tidss/tidss_irq.c
> @@ -60,7 +60,9 @@ static irqreturn_t tidss_irq_handler(int irq, void *arg)
>         unsigned int id;
>         dispc_irq_t irqstatus;
>
> +       spin_lock(&tidss->wait_lock);
>         irqstatus = dispc_read_and_clear_irqstatus(tidss->dispc);
> +       spin_unlock(&tidss->wait_lock);
>
>         for (id = 0; id < tidss->num_crtcs; id++) {
>                 struct drm_crtc *crtc = tidss->crtcs[id];
>
> --
> 2.43.0
>