[PATCH v8 2/2] drm: add kms driver for loongson display controller

[kernel test robot]

Hi Sui,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v6.3-rc4 next-20230328]
[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/Sui-Jingfeng/MAINTAINERS-add-maintainers-for-DRM-LOONGSON-driver/20230320-180408
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230320100131.1277034-3-15330273260%40189.cn
patch subject: [PATCH v8 2/2] drm: add kms driver for loongson display controller
config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20230328/202303281754.jWI20j2C-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/80b4115f44993f4ebf47b1cb9e8f02953575b977
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Sui-Jingfeng/MAINTAINERS-add-maintainers-for-DRM-LOONGSON-driver/20230320-180408
        git checkout 80b4115f44993f4ebf47b1cb9e8f02953575b977
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/accel/ drivers/gpu/drm/loongson/ drivers/iio/light/ drivers/media/pci/intel/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp at intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303281754.jWI20j2C-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/gpu/drm/loongson/lsdc_drv.c:232:11: warning: variable 'gpu' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           else if (descp->chip == CHIP_LS7A2000)
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/gpu/drm/loongson/lsdc_drv.c:235:7: note: uninitialized use occurs here
           if (!gpu) {
                ^~~
   drivers/gpu/drm/loongson/lsdc_drv.c:232:7: note: remove the 'if' if its condition is always true
           else if (descp->chip == CHIP_LS7A2000)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/gpu/drm/loongson/lsdc_drv.c:217:21: note: initialize the variable 'gpu' to silence this warning
           struct pci_dev *gpu;
                              ^
                               = NULL
   1 warning generated.
--
>> drivers/gpu/drm/loongson/lsdc_pll.c:188:14: warning: variable 'diff' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
                                   else if (clock_khz < computed)
                                            ^~~~~~~~~~~~~~~~~~~~
   drivers/gpu/drm/loongson/lsdc_pll.c:191:9: note: uninitialized use occurs here
                                   if (diff < min) {
                                       ^~~~
   drivers/gpu/drm/loongson/lsdc_pll.c:188:10: note: remove the 'if' if its condition is always true
                                   else if (clock_khz < computed)
                                        ^~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/gpu/drm/loongson/lsdc_pll.c:177:22: note: initialize the variable 'diff' to silence this warning
                                   unsigned int diff;
                                                    ^
                                                     = 0
   1 warning generated.


vim +232 drivers/gpu/drm/loongson/lsdc_drv.c

   212	
   213	static int lsdc_get_dedicated_vram(struct lsdc_device *ldev,
   214					   const struct lsdc_desc *descp)
   215	{
   216		struct drm_device *ddev = &ldev->base;
   217		struct pci_dev *gpu;
   218		resource_size_t base, size;
   219	
   220		/*
   221		 * The GPU and display controller in LS7A1000/LS7A2000 are separated
   222		 * PCIE devices, they are two devices not one. The DC does not has a
   223		 * dedicate VRAM bar, because the BIOS engineer choose to assign the
   224		 * VRAM to the GPU device. Sadly, after years application, this form
   225		 * as a convention for loongson integrated graphics. Bar 2 of the GPU
   226		 * device contain the base address and size of the VRAM, both the GPU
   227		 * and the DC can access the on-board VRAM as long as the DMA address
   228		 * emitted fall in [base, base + size).
   229		 */
   230		if (descp->chip == CHIP_LS7A1000)
   231			gpu = pci_get_device(PCI_VENDOR_ID_LOONGSON, 0x7A15, NULL);
 > 232		else if (descp->chip == CHIP_LS7A2000)
   233			gpu = pci_get_device(PCI_VENDOR_ID_LOONGSON, 0x7A25, NULL);
   234	
   235		if (!gpu) {
   236			drm_warn(ddev, "No GPU device found\n");
   237			return -ENODEV;
   238		}
   239	
   240		base = pci_resource_start(gpu, 2);
   241		size = pci_resource_len(gpu, 2);
   242	
   243		ldev->vram_base = base;
   244		ldev->vram_size = size;
   245	
   246		drm_info(ddev, "dedicated vram start: 0x%llx, size: %uMB\n",
   247			 (u64)base, (u32)(size >> 20));
   248	
   249		return 0;
   250	}
   251	

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