linux-kernel - [PATCH] drm/rockchip: avoid duplicate mappings for IOMMU devices

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Message-Id: <20221110172415.2853420-1-john@metanate.com>
Date:   Thu, 10 Nov 2022 17:24:14 +0000
From:   John Keeping <john@...anate.com>
To:     Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>
Cc:     John Keeping <john@...anate.com>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/rockchip: avoid duplicate mappings for IOMMU devices

If a buffer is allocated with alloc_kmap, then it is vmap'd on creation
and there is no reason to map it again in rockchip_gem_prime_vmap() when
the existing mapping can be used.

Signed-off-by: John Keeping <john@...anate.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
index 6edb7c52cb3d..c9507d27f0ba 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
@@ -519,8 +519,14 @@ int rockchip_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
 
 	if (rk_obj->pages) {
-		void *vaddr = vmap(rk_obj->pages, rk_obj->num_pages, VM_MAP,
-				  pgprot_writecombine(PAGE_KERNEL));
+		void *vaddr;
+
+		if (rk_obj->kvaddr)
+			vaddr = rk_obj->kvaddr;
+		else
+			vaddr = vmap(rk_obj->pages, rk_obj->num_pages, VM_MAP,
+				     pgprot_writecombine(PAGE_KERNEL));
+
 		if (!vaddr)
 			return -ENOMEM;
 		iosys_map_set_vaddr(map, vaddr);
@@ -540,7 +546,8 @@ void rockchip_gem_prime_vunmap(struct drm_gem_object *obj,
 	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
 
 	if (rk_obj->pages) {
-		vunmap(map->vaddr);
+		if (map->vaddr != rk_obj->kvaddr)
+			vunmap(map->vaddr);
 		return;
 	}
 
-- 
2.38.1