Re: [PATCH] drm/display/dsc: Refactor MST DSC Determination Policy

[kernel test robot <lkp@intel.com>]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20240919173944.256887-1-Jerry.Zuo@amd.com>
References: <20240919173944.256887-1-Jerry.Zuo@amd.com>
TO: Fangzhi Zuo <Jerry.Zuo@amd.com>
TO: dri-devel@lists.freedesktop.org
TO: intel-gfx@lists.freedesktop.org
TO: amd-gfx@lists.freedesktop.org
TO: lyude@redhat.com
TO: jani.nikula@intel.com
TO: imre.deak@intel.com
TO: simona@ffwll.ch
TO: wayne.lin@amd.com
TO: Harry.Wentland@amd.com
TO: rodrigo.siqueira@amd.com
CC: Fangzhi Zuo <Jerry.Zuo@amd.com>

Hi Fangzhi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-intel/for-linux-next]
[also build test WARNING on drm/drm-next linus/master]
[cannot apply to drm-intel/for-linux-next-fixes drm-tip/drm-tip drm-exynos/exynos-drm-next drm-misc/drm-misc-next v6.11 next-20240920]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Fangzhi-Zuo/drm-display-dsc-Refactor-MST-DSC-Determination-Policy/20240920-014114
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
patch link:    https://lore.kernel.org/r/20240919173944.256887-1-Jerry.Zuo%40amd.com
patch subject: [PATCH] drm/display/dsc: Refactor MST DSC Determination Policy
:::::: branch date: 3 days ago
:::::: commit date: 3 days ago
config: microblaze-randconfig-r071-20240922 (https://download.01.org/0day-ci/archive/20240923/202409231002.bMP89Ipm-lkp@intel.com/config)
compiler: microblaze-linux-gcc (GCC) 14.1.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202409231002.bMP89Ipm-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/display/drm_dp_mst_topology.c:6046 drm_dp_mst_dsc_aux_for_port() warn: variable dereferenced before check 'port' (see line 6035)

vim +/port +6046 drivers/gpu/drm/display/drm_dp_mst_topology.c

93cb4094a7fd30 drivers/gpu/drm/display/drm_dp_mst_topology.c Imre Deak        2024-04-17  6015  
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6016  /**
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6017   * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6018   * @port: The port to check. A leaf of the MST tree with an attached display.
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6019   *
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6020   * Depending on the situation, DSC may be enabled via the endpoint aux,
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6021   * the immediately upstream aux, or the connector's physical aux.
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6022   *
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6023   * This is both the correct aux to read DSC_CAPABILITY and the
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6024   * correct aux to write DSC_ENABLED.
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6025   *
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6026   * This operation can be expensive (up to four aux reads), so
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6027   * the caller should cache the return.
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6028   *
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6029   * port->dsc_aux - point for dsc decompression
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6030   * port->dsc_passthrough_aux - point for dsc passthrough
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6031   *
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6032   */
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6033  void drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6034  {
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19 @6035  	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6036  	struct drm_dp_mst_port *immediate_upstream_port = NULL;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6037  	struct drm_dp_mst_port *fec_port = NULL;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6038  	struct drm_dp_mst_port *dsc_port = NULL;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6039  	struct drm_dp_aux *upstream_aux;
53965dbe5396d2 drivers/gpu/drm/drm_dp_mst_topology.c         Paul E. McKenney 2020-02-19  6040  	struct drm_dp_desc desc = {};
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6041  	bool end_has_dpcd = (port->dpcd_rev > 0);
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6042  	u8 endpoint_dsc = 0;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6043  	u8 upstream_dsc;
cc707186414576 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo      2024-09-19  6044  	u8 fec_cap;
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26  6045  
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis    2019-08-26 @6046  	if (!port)

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