Re: [PATCH v8 2/2] drm: add kms driver for loongson display controller
From: Sui Jingfeng
Date: Tue Mar 28 2023 - 11:29:40 EST
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@xxxxxxxxx/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@xxxxxxxxx>
| Link: https://lore.kernel.org/oe-kbuild-all/202303281754.jWI20j2C-lkp@xxxxxxxxx/
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