linux-kernel - [PATCH] drm/i915: Fix 32-bit build

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Date:   Sun, 17 Jul 2022 09:20:46 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Matthew Auld <matthew.auld@...el.com>,
        Nirmoy Das <nirmoy.das@...el.com>
Subject: [PATCH] drm/i915: Fix 32-bit build

Commit aff1e0b09b54 ("drm/i915/ttm: fix sg_table construction") introduces
an additional parameter to i915_rsgt_from_mm_node(). The parameter is used
to calculate segment_pages. This in turn is used in DIV_ROUND_UP() as
divisor. So far segment_pages was a constant and handled without divide
operation. Since it is no longer constant, a divide operation is now
necessary. This results in build errors on 32-bit builds.

x86_64-linux-ld: drivers/gpu/drm/i915/i915_scatterlist.o:
	in function `i915_rsgt_from_mm_node':
i915_scatterlist.c:(.text+0x196): undefined reference to `__udivdi3'

Fix the problem by using DIV_ROUND_UP_ULL() instead of DIV_ROUND_UP().

Fixes: aff1e0b09b54 ("drm/i915/ttm: fix sg_table construction")
Cc: Matthew Auld <matthew.auld@...el.com>
Cc: Nirmoy Das <nirmoy.das@...el.com>
Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
I took a stab at the problem. Please ignore the noise if it has already
been fixed with a different patch.

 drivers/gpu/drm/i915/i915_scatterlist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_scatterlist.c b/drivers/gpu/drm/i915/i915_scatterlist.c
index f63b50b71e10..b81d5658c222 100644
--- a/drivers/gpu/drm/i915/i915_scatterlist.c
+++ b/drivers/gpu/drm/i915/i915_scatterlist.c
@@ -96,7 +96,7 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
 
 	i915_refct_sgt_init(rsgt, node->size << PAGE_SHIFT);
 	st = &rsgt->table;
-	if (sg_alloc_table(st, DIV_ROUND_UP(node->size, segment_pages),
+	if (sg_alloc_table(st, DIV_ROUND_UP_ULL(node->size, segment_pages),
 			   GFP_KERNEL)) {
 		i915_refct_sgt_put(rsgt);
 		return ERR_PTR(-ENOMEM);
-- 
2.36.2