Re: [PATCH] spi: spi-mem: rtl-snand: Correctly handle DMA transfers

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

Hi Chris,

kernel test robot noticed the following build warnings:

[auto build test WARNING on broonie-spi/for-next]
[also build test WARNING on next-20241029]
[cannot apply to linus/master v6.12-rc5]
[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/Chris-Packham/spi-spi-mem-rtl-snand-Correctly-handle-DMA-transfers/20241030-055313
base:   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next
patch link:    https://lore.kernel.org/r/20241029215159.1975844-1-chris.packham%40alliedtelesis.co.nz
patch subject: [PATCH] spi: spi-mem: rtl-snand: Correctly handle DMA transfers
config: m68k-allmodconfig (https://download.01.org/0day-ci/archive/20241030/202410301452.7koB3V8S-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 14.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241030/202410301452.7koB3V8S-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/202410301452.7koB3V8S-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/spi/spi-realtek-rtl-snand.c: In function 'rtl_snand_dma_xfer':
>> drivers/spi/spi-realtek-rtl-snand.c:252:21: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
     252 |                 buf = op->data.buf.out;
         |                     ^

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for GET_FREE_REGION
   Depends on [n]: SPARSEMEM [=n]
   Selected by [m]:
   - RESOURCE_KUNIT_TEST [=m] && RUNTIME_TESTING_MENU [=y] && KUNIT [=m]


vim +/const +252 drivers/spi/spi-realtek-rtl-snand.c

   231	
   232	static int rtl_snand_dma_xfer(struct rtl_snand *snand, int cs, const struct spi_mem_op *op)
   233	{
   234		unsigned int pos, nbytes;
   235		int ret;
   236		dma_addr_t buf_dma;
   237		enum dma_data_direction dir;
   238		u32 trig, len, maxlen;
   239		void *buf;
   240	
   241		ret = rtl_snand_xfer_head(snand, cs, op);
   242		if (ret)
   243			goto out_deselect;
   244	
   245		if (op->data.dir == SPI_MEM_DATA_IN) {
   246			maxlen = 2080;
   247			buf = op->data.buf.in;
   248			dir = DMA_FROM_DEVICE;
   249			trig = 0;
   250		} else if (op->data.dir == SPI_MEM_DATA_OUT) {
   251			maxlen = 520;
 > 252			buf = op->data.buf.out;
   253			dir = DMA_TO_DEVICE;
   254			trig = 1;
   255		} else {
   256			ret = -EOPNOTSUPP;
   257			goto out_deselect;
   258		}
   259	
   260		buf_dma = dma_map_single(snand->dev, buf, op->data.nbytes, dir);
   261		ret = dma_mapping_error(snand->dev, buf_dma);
   262		if (ret)
   263			goto out_deselect;
   264	
   265		ret = regmap_write(snand->regmap, SNAFDIR, SNAFDIR_DMA_IP);
   266		if (ret)
   267			goto out_unmap;
   268	
   269		ret = regmap_update_bits(snand->regmap, SNAFCFR, SNAFCFR_DMA_IE, SNAFCFR_DMA_IE);
   270		if (ret)
   271			goto out_unmap;
   272	
   273		pos = 0;
   274		len = op->data.nbytes;
   275	
   276		while (pos < len) {
   277			nbytes = len - pos;
   278			if (nbytes > maxlen)
   279				nbytes = maxlen;
   280	
   281			reinit_completion(&snand->comp);
   282	
   283			ret = regmap_write(snand->regmap, SNAFDRSAR, buf_dma + pos);
   284			if (ret)
   285				goto out_disable_int;
   286	
   287			pos += nbytes;
   288	
   289			ret = regmap_write(snand->regmap, SNAFDLR,
   290					CMR_WID(op->data.buswidth) | nbytes);
   291			if (ret)
   292				goto out_disable_int;
   293	
   294			ret = regmap_write(snand->regmap, SNAFDTR, trig);
   295			if (ret)
   296				goto out_disable_int;
   297	
   298			if (!wait_for_completion_timeout(&snand->comp, usecs_to_jiffies(20000)))
   299				ret = -ETIMEDOUT;
   300	
   301			if (ret)
   302				goto out_disable_int;
   303		}
   304	
   305	out_disable_int:
   306		regmap_update_bits(snand->regmap, SNAFCFR, SNAFCFR_DMA_IE, 0);
   307	out_unmap:
   308		dma_unmap_single(snand->dev, buf_dma, op->data.nbytes, dir);
   309	out_deselect:
   310		rtl_snand_xfer_tail(snand, cs);
   311	
   312		if (ret)
   313			dev_err(snand->dev, "transfer failed %d\n", ret);
   314	
   315		return ret;
   316	}
   317	

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