linux-kernel - Re: [PATCH 1/1] drm/radeon: check return value of radeon_ring

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Message-ID: <325dd89e-aa25-3346-d622-c49528f4e68d@vodafone.de>
Date:   Mon, 24 Apr 2017 09:47:35 +0200
From:   Christian König <deathsimple@...afone.de>
To:     Pan Bian <bianpan201603@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>
Cc:     Pan Bian <bianpan2016@....com>, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] drm/radeon: check return value of radeon_ring_lock

Am 23.04.2017 um 15:36 schrieb Pan Bian:
> From: Pan Bian <bianpan2016@....com>
>
> Function radeon_ring_lock() returns an errno on failure, and its return
> value should be validated. However, in functions r420_cp_errata_init()
> and r420_cp_errata_fini(), its return value is not checked. This patch
> adds the checks.
>
> Signed-off-by: Pan Bian <bianpan2016@....com>
> ---
>   drivers/gpu/drm/radeon/r420.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/r420.c b/drivers/gpu/drm/radeon/r420.c
> index 2828605..a8c2b37 100644
> --- a/drivers/gpu/drm/radeon/r420.c
> +++ b/drivers/gpu/drm/radeon/r420.c
> @@ -215,7 +215,8 @@ static void r420_cp_errata_init(struct radeon_device *rdev)
>   	 * of the CP init, apparently.
>   	 */
>   	radeon_scratch_get(rdev, &rdev->config.r300.resync_scratch);
> -	radeon_ring_lock(rdev, ring, 8);
> +	if (radeon_ring_lock(rdev, ring, 8))
> +		return;

Nice that somebody wants to clean that up, but just returning here is 
not a good idea.

Additional to that radeon_ring_lock() can only fail if we try to 
allocate to many dw (impossible with only 8) or the hardware is crashed 
and then it doesn't matter anyway.

I suggest to just add a WARN_ON() here.

Regards,
Christian.

>   	radeon_ring_write(ring, PACKET0(R300_CP_RESYNC_ADDR, 1));
>   	radeon_ring_write(ring, rdev->config.r300.resync_scratch);
>   	radeon_ring_write(ring, 0xDEADBEEF);
> @@ -229,7 +230,8 @@ static void r420_cp_errata_fini(struct radeon_device *rdev)
>   	/* Catch the RESYNC we dispatched all the way back,
>   	 * at the very beginning of the CP init.
>   	 */
> -	radeon_ring_lock(rdev, ring, 8);
> +	if (radeon_ring_lock(rdev, ring, 8))
> +		return;
>   	radeon_ring_write(ring, PACKET0(R300_RB3D_DSTCACHE_CTLSTAT, 0));
>   	radeon_ring_write(ring, R300_RB3D_DC_FINISH);
>   	radeon_ring_unlock_commit(rdev, ring, false);