linux-kernel - [PATCH 2/3] [v2] drm/xe/mmio: fix build warning for BAR resize on 32-bit

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Date: Mon, 26 Feb 2024 13:46:37 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Lucas De Marchi <lucas.demarchi@...el.com>,
	Oded Gabbay <ogabbay@...nel.org>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Matt Roper <matthew.d.roper@...el.com>,
	Matthew Auld <matthew.auld@...el.com>,
	Matthew Brost <matthew.brost@...el.com>,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH 2/3] [v2] drm/xe/mmio: fix build warning for BAR resize on 32-bit

From: Arnd Bergmann <arnd@...db.de>

clang complains about a nonsensical test on builds with a 32-bit phys_addr_t,
which means resizing will always fail:

drivers/gpu/drm/xe/xe_mmio.c:109:23: error: result of comparison of constant 4294967296 with expression of type 'resource_size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
  109 |                     root_res->start > 0x100000000ull)
      |                     ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~

Previously, BAR resize was always disallowed on 32-bit kernels, but
this apparently changed recently. Since 32-bit machines can in theory
support PAE/LPAE for large address spaces, this may end up useful,
so change the driver to shut up the warning but still work when
phys_addr_t/resource_size_t is 64 bit wide.

Fixes: 9a6e6c14bfde ("drm/xe/mmio: Use non-atomic writeq/readq variant for 32b")
Fixes: 237412e45390 ("drm/xe: Enable 32bits build")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: use correct Fixes tag
---
 drivers/gpu/drm/xe/xe_mmio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
index e3db3a178760..7ba2477452d7 100644
--- a/drivers/gpu/drm/xe/xe_mmio.c
+++ b/drivers/gpu/drm/xe/xe_mmio.c
@@ -106,7 +106,7 @@ static void xe_resize_vram_bar(struct xe_device *xe)
 
 	pci_bus_for_each_resource(root, root_res, i) {
 		if (root_res && root_res->flags & (IORESOURCE_MEM | IORESOURCE_MEM_64) &&
-		    root_res->start > 0x100000000ull)
+		    (u64)root_res->start > 0x100000000ul)
 			break;
 	}
 
-- 
2.39.2