Re: [PATCH 14/14] dmaengine: dma350: Support ARM DMA-250

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

Hi Jisheng,

kernel test robot noticed the following build warnings:

[auto build test WARNING on vkoul-dmaengine/next]
[also build test WARNING on robh/for-next krzk-dt/for-next linus/master v6.17-rc2 next-20250822]
[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/Jisheng-Zhang/dmaengine-dma350-Fix-CH_CTRL_USESRCTRIGIN-definition/20250824-000425
base:   https://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine.git next
patch link:    https://lore.kernel.org/r/20250823154009.25992-15-jszhang%40kernel.org
patch subject: [PATCH 14/14] dmaengine: dma350: Support ARM DMA-250
config: x86_64-buildonly-randconfig-002-20250824 (https://download.01.org/0day-ci/archive/20250825/202508250351.vxyvTsJa-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250825/202508250351.vxyvTsJa-lkp@intel.com/reproduce)

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>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508250351.vxyvTsJa-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/dma/arm-dma350.c:849:34: warning: variable 'sg' is uninitialized when used here [-Wuninitialized]
     849 |         sglen = DIV_ROUND_UP(sg_dma_len(sg), step_max) * periods;
         |                                         ^~
   include/linux/scatterlist.h:34:27: note: expanded from macro 'sg_dma_len'
      34 | #define sg_dma_len(sg)          ((sg)->dma_length)
         |                                   ^~
   include/uapi/linux/const.h:51:40: note: expanded from macro '__KERNEL_DIV_ROUND_UP'
      51 | #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
         |                                        ^
   drivers/dma/arm-dma350.c:835:24: note: initialize the variable 'sg' to silence this warning
     835 |         struct scatterlist *sg;
         |                               ^
         |                                = NULL
   1 warning generated.


vim +/sg +849 drivers/dma/arm-dma350.c

   824	
   825	static struct dma_async_tx_descriptor *
   826	d250_prep_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
   827			 size_t buf_len, size_t period_len, enum dma_transfer_direction dir,
   828			 unsigned long flags)
   829	{
   830		struct d350_chan *dch = to_d350_chan(chan);
   831		u32 len, periods, trig, *cmd, tsz;
   832		dma_addr_t src, dst, phys, mem_addr;
   833		size_t xfer_len, step_max;
   834		struct d350_desc *desc;
   835		struct scatterlist *sg;
   836		struct d350_sg *dsg;
   837		int sglen, i;
   838	
   839		if (unlikely(!is_slave_direction(dir) || !buf_len || !period_len))
   840			return NULL;
   841	
   842		if (dir == DMA_MEM_TO_DEV)
   843			tsz = __ffs(dch->config.dst_addr_width | (1 << dch->tsz));
   844		else
   845			tsz = __ffs(dch->config.src_addr_width | (1 << dch->tsz));
   846		step_max = ((1UL << 16) - 1) << tsz;
   847	
   848		periods = buf_len / period_len;
 > 849		sglen = DIV_ROUND_UP(sg_dma_len(sg), step_max) * periods;
   850	
   851		desc = kzalloc(struct_size(desc, sg, sglen), GFP_NOWAIT);
   852		if (!desc)
   853			return NULL;
   854	
   855		dch->cyclic = true;
   856		dch->periods = periods;
   857		desc->sglen = sglen;
   858	
   859		sglen = 0;
   860		for (i = 0; i < periods; i++) {
   861			len = period_len;
   862			mem_addr = buf_addr + i * period_len;
   863			do {
   864				desc->sg[sglen].command = dma_pool_zalloc(dch->cmd_pool, GFP_NOWAIT, &phys);
   865				if (unlikely(!desc->sg[sglen].command))
   866					goto err_cmd_alloc;
   867	
   868				xfer_len = (len > step_max) ? step_max : len;
   869				desc->sg[sglen].phys = phys;
   870				dsg = &desc->sg[sglen];
   871	
   872				if (dir == DMA_MEM_TO_DEV) {
   873					src = mem_addr;
   874					dst = dch->config.dst_addr;
   875					trig = CH_CTRL_USEDESTRIGIN;
   876				} else {
   877					src = dch->config.src_addr;
   878					dst = mem_addr;
   879					trig = CH_CTRL_USESRCTRIGIN;
   880				}
   881				dsg->tsz = tsz;
   882				dsg->xsize = lower_16_bits(xfer_len >> dsg->tsz);
   883	
   884				cmd = dsg->command;
   885				cmd[0] = LINK_CTRL | LINK_SRCADDR | LINK_DESADDR |
   886					 LINK_XSIZE | LINK_SRCTRANSCFG |
   887					 LINK_DESTRANSCFG | LINK_XADDRINC | LINK_LINKADDR;
   888	
   889				cmd[1] = FIELD_PREP(CH_CTRL_TRANSIZE, dsg->tsz) |
   890					 FIELD_PREP(CH_CTRL_XTYPE, CH_CTRL_XTYPE_CONTINUE) |
   891					 FIELD_PREP(CH_CTRL_DONETYPE, CH_CTRL_DONETYPE_CMD) | trig;
   892	
   893				cmd[2] = lower_32_bits(src);
   894				cmd[3] = lower_32_bits(dst);
   895				cmd[4] = FIELD_PREP(CH_XY_SRC, dsg->xsize) |
   896					 FIELD_PREP(CH_XY_DES, dsg->xsize);
   897				if (dir == DMA_MEM_TO_DEV) {
   898					cmd[0] |= LINK_DESTRIGINCFG;
   899					cmd[5] = dch->coherent ? TRANSCFG_WB : TRANSCFG_NC;
   900					cmd[6] = TRANSCFG_DEVICE;
   901					cmd[7] = FIELD_PREP(CH_XY_SRC, 1);
   902					cmd[8] = FIELD_PREP(CH_DESTRIGINMODE, CH_DESTRIG_DMA_FC) |
   903						  FIELD_PREP(CH_DESTRIGINTYPE, CH_DESTRIG_HW_REQ);
   904				} else {
   905					cmd[0] |= LINK_SRCTRIGINCFG;
   906					cmd[5] = TRANSCFG_DEVICE;
   907					cmd[6] = dch->coherent ? TRANSCFG_WB : TRANSCFG_NC;
   908					cmd[7] = FIELD_PREP(CH_XY_DES, 1);
   909					cmd[8] = FIELD_PREP(CH_SRCTRIGINMODE, CH_SRCTRIG_DMA_FC) |
   910						  FIELD_PREP(CH_SRCTRIGINTYPE, CH_SRCTRIG_HW_REQ);
   911				}
   912	
   913				if (sglen)
   914					desc->sg[sglen - 1].command[9] = phys | CH_LINKADDR_EN;
   915	
   916				len -= xfer_len;
   917				mem_addr += xfer_len;
   918				sglen++;
   919			} while (len);
   920			desc->sg[sglen - 1].command[1] |= FIELD_PREP(CH_CTRL_DONETYPE,
   921								     CH_CTRL_DONETYPE_CMD);
   922		}
   923	
   924		/* cyclic list */
   925		desc->sg[sglen - 1].command[9] = desc->sg[0].phys | CH_LINKADDR_EN;
   926	
   927		mb();
   928	
   929		return vchan_tx_prep(&dch->vc, &desc->vd, flags);
   930	
   931	err_cmd_alloc:
   932		for (i = 0; i < sglen; i++)
   933			dma_pool_free(dch->cmd_pool, desc->sg[i].command, desc->sg[i].phys);
   934		kfree(desc);
   935		return NULL;
   936	}
   937	

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