[RFC] drm/msm: Disallow relocs on a6xx+

[Rob Clark <robdclark@gmail.com>]

From: Rob Clark <robdclark@chromium.org>

Mesa stopped using these pretty early in a6xx bringup.  Take advantage
of this to disallow some legacy UABI.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
So, it was late 2018 when mesa stopped using relocs.  At that point a6xx
support was still in a pretty early state.  I guess you _could_ use such
an old version of mesa with a6xx hw.. but you really shouldn't.

 drivers/gpu/drm/msm/adreno/adreno_gpu.c |  2 ++
 drivers/gpu/drm/msm/msm_gem_submit.c    | 10 ++++++++++
 drivers/gpu/drm/msm/msm_gpu.h           |  9 +++++++++
 3 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index ba35c2a87021..695cce82d914 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -1078,6 +1078,8 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
 	adreno_gpu->info = config->info;
 	adreno_gpu->chip_id = config->chip_id;
 
+	gpu->allow_relocs = config->info->family < ADRENO_6XX_GEN1;
+
 	/* Only handle the core clock when GMU is not in use (or is absent). */
 	if (adreno_has_gmu_wrapper(adreno_gpu) ||
 	    adreno_gpu->info->family < ADRENO_6XX_GEN1) {
diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
index 63c96416e183..3b908f9f5493 100644
--- a/drivers/gpu/drm/msm/msm_gem_submit.c
+++ b/drivers/gpu/drm/msm/msm_gem_submit.c
@@ -882,6 +882,16 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 		if (submit->valid)
 			continue;
 
+		if (!gpu->allow_relocs) {
+			if (submit->cmd[i].nr_relocs) {
+				DRM_ERROR("relocs not allowed\n");
+				ret = -EINVAL;
+				goto out;
+			}
+
+			continue;
+		}
+
 		ret = submit_reloc(submit, msm_obj, submit->cmd[i].offset * 4,
 				submit->cmd[i].nr_relocs, submit->cmd[i].relocs);
 		if (ret)
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 7a4fa1b8655b..4252e3839fbc 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -285,6 +285,15 @@ struct msm_gpu {
 	/* True if the hardware supports expanded apriv (a650 and newer) */
 	bool hw_apriv;
 
+	/**
+	 * @allow_relocs: allow relocs in SUBMIT ioctl
+	 *
+	 * Mesa won't use relocs for driver version 1.4.0 and later.  This
+	 * switch-over happened early enough in mesa a6xx bringup that we
+	 * can disallow relocs for a6xx and newer.
+	 */
+	bool allow_relocs;
+
 	struct thermal_cooling_device *cooling;
 };
 
-- 
2.41.0