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Message-ID: <027cf6d5-6de2-3424-7a81-a43ab689c3d4@189.cn>
Date: Tue, 28 Mar 2023 23:22:50 +0800
From: Sui Jingfeng <15330273260@....cn>
To: kernel test robot <lkp@...el.com>,
Sui Jingfeng <15330273260@....cn>,
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>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian Koenig <christian.koenig@....com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
Li Yi <liyi@...ngson.cn>
Subject: Re: [PATCH v8 2/2] drm: add kms driver for loongson display
controller
HI,
On 2023/3/28 17:27, kernel test robot wrote:
> 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@...el.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.
> --
In practice, either descp->chip == CHIP_LS7A2000 or descp->chip ==
CHIP_LS7A1000 will be happened at runtime.
the variable 'gpu' is guaranteed to be initialized when code run at
drivers/gpu/drm/loongson/lsdc_drv.c:235
This warnning is almost wrong here.
>>> 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.
Here the robot is also wrong here in practice,
because either if (clock_khz >= computed) or else if (clock_khz <
computed) will be happen.
'diff' variable is guaranteed to be initialized.
>
> 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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