[PATCH] drm/amd/display: add missing NULL check for DML2

[Bob Zhou]

Recently, the driver introduce DML2 for future ASIC support.
But, some ASIC's hubbub pointer is null before calling.
It cause the below null pointer issue, so add null check to fix it.

BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:dc_create_resource_pool+0xc1/0x2c0 [amdgpu] Call Trace:
 <TASK>
 ? show_regs.cold+0x1a/0x1f
 ? __die_body+0x20/0x70
 ? __die+0x2b/0x37
 ? page_fault_oops+0x136/0x2c0
 ? do_user_addr_fault+0x303/0x660
 ? exc_page_fault+0x77/0x170
 ? asm_exc_page_fault+0x27/0x30
 ? dc_create_resource_pool+0xc1/0x2c0 [amdgpu]  ? dc_create_resource_pool+0x243/0x2c0 [amdgpu]
 dc_create+0x23f/0x6b0 [amdgpu]
 ? dmi_matches+0xa3/0x200
 amdgpu_dm_init+0x2bd/0x22a0 [amdgpu]

Fixes: a2815ada8616 ("drm/amd/display: Introduce DML2")

Signed-off-by: Bob Zhou <bob.zhou at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
index 25562b262555..d20e01226353 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -321,7 +321,7 @@ struct resource_pool *dc_create_resource_pool(struct dc  *dc,
 				res_pool->ref_clocks.xtalin_clock_inKhz;
 			res_pool->ref_clocks.dchub_ref_clock_inKhz =
 				res_pool->ref_clocks.xtalin_clock_inKhz;
-			if ((res_pool->hubbub->funcs->get_dchub_ref_freq))
+			if (res_pool->hubbub && res_pool->hubbub->funcs->get_dchub_ref_freq)
 				res_pool->hubbub->funcs->get_dchub_ref_freq(res_pool->hubbub,
 					res_pool->ref_clocks.dccg_ref_clock_inKhz,
 					&res_pool->ref_clocks.dchub_ref_clock_inKhz);
-- 
2.34.1