diff mbox series

spi: spi-mem: rtl-snand: Correctly handle DMA transfers

Message ID 20241029215159.1975844-1-chris.packham@alliedtelesis.co.nz
State Superseded
Headers show
Series spi: spi-mem: rtl-snand: Correctly handle DMA transfers | expand

Commit Message

Chris Packham Oct. 29, 2024, 9:51 p.m. UTC 
The RTL9300 has some limitations on the maximum DMA transfers possible.
For reads this is 2080 bytes (520*4) for writes this is 520 bytes. Deal
with this by splitting transfers into appropriately sized parts. Also
ensure that we are using the correct buffer when doing DMA writes.

Fixes: 42d20a6a61b8 ("spi: spi-mem: Add Realtek SPI-NAND controller")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
 drivers/spi/spi-realtek-rtl-snand.c | 51 +++++++++++++++++++----------
 1 file changed, 34 insertions(+), 17 deletions(-)

Comments

kernel test robot Oct. 30, 2024, 6:42 a.m. UTC | #1 
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
kernel test robot Oct. 30, 2024, 10:20 a.m. UTC | #2 
Hi Chris,

kernel test robot noticed the following build errors:

[auto build test ERROR on broonie-spi/for-next]
[also build test ERROR 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: s390-allmodconfig (https://download.01.org/0day-ci/archive/20241030/202410301731.MOPjsQ0R-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 639a7ac648f1e50ccd2556e17d401c04f9cce625)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241030/202410301731.MOPjsQ0R-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/202410301731.MOPjsQ0R-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/spi/spi-realtek-rtl-snand.c:4:
   In file included from include/linux/dma-mapping.h:8:
   In file included from include/linux/device.h:32:
   In file included from include/linux/device/driver.h:21:
   In file included from include/linux/module.h:19:
   In file included from include/linux/elf.h:6:
   In file included from arch/s390/include/asm/elf.h:181:
   In file included from arch/s390/include/asm/mmu_context.h:11:
   In file included from arch/s390/include/asm/pgalloc.h:18:
   In file included from include/linux/mm.h:2213:
   include/linux/vmstat.h:504:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     504 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     505 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:511:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     511 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     512 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:524:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     524 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     525 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/spi/spi-realtek-rtl-snand.c:4:
   In file included from include/linux/dma-mapping.h:11:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:93:
   include/asm-generic/io.h:548:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     548 |         val = __raw_readb(PCI_IOBASE + addr);
         |                           ~~~~~~~~~~ ^
   include/asm-generic/io.h:561:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     561 |         val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
      37 | #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
         |                                                           ^
   include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
     102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
         |                                                      ^
   In file included from drivers/spi/spi-realtek-rtl-snand.c:4:
   In file included from include/linux/dma-mapping.h:11:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:93:
   include/asm-generic/io.h:574:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     574 |         val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
      35 | #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
         |                                                           ^
   include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
     115 | #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
         |                                                      ^
   In file included from drivers/spi/spi-realtek-rtl-snand.c:4:
   In file included from include/linux/dma-mapping.h:11:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:93:
   include/asm-generic/io.h:585:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     585 |         __raw_writeb(value, PCI_IOBASE + addr);
         |                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:595:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     595 |         __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:605:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     605 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:693:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     693 |         readsb(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:701:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     701 |         readsw(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:709:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     709 |         readsl(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:718:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     718 |         writesb(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:727:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     727 |         writesw(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:736:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     736 |         writesl(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
>> drivers/spi/spi-realtek-rtl-snand.c:252:7: error: assigning to 'void *' from 'const void *const' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
     252 |                 buf = op->data.buf.out;
         |                     ^ ~~~~~~~~~~~~~~~~
   16 warnings and 1 error generated.


vim +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
kernel test robot Oct. 30, 2024, 7:53 p.m. UTC | #3 
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-20241030]
[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: nios2-randconfig-r131-20241030 (https://download.01.org/0day-ci/archive/20241031/202410310358.GyKQwhxO-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 14.1.0
reproduce: (https://download.01.org/0day-ci/archive/20241031/202410310358.GyKQwhxO-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/202410310358.GyKQwhxO-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/spi/spi-realtek-rtl-snand.c:252:21: sparse: sparse: incorrect type in assignment (different modifiers) @@     expected void *[assigned] buf @@     got void const *const out @@
   drivers/spi/spi-realtek-rtl-snand.c:252:21: sparse:     expected void *[assigned] buf
   drivers/spi/spi-realtek-rtl-snand.c:252:21: sparse:     got void const *const out

vim +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
diff mbox series

Patch

diff --git a/drivers/spi/spi-realtek-rtl-snand.c b/drivers/spi/spi-realtek-rtl-snand.c
index 23c42c8469e4..50b3240641e8 100644
--- a/drivers/spi/spi-realtek-rtl-snand.c
+++ b/drivers/spi/spi-realtek-rtl-snand.c
@@ -231,19 +231,25 @@  static int rtl_snand_xfer(struct rtl_snand *snand, int cs, const struct spi_mem_
 
 static int rtl_snand_dma_xfer(struct rtl_snand *snand, int cs, const struct spi_mem_op *op)
 {
+	unsigned int pos, nbytes;
 	int ret;
 	dma_addr_t buf_dma;
 	enum dma_data_direction dir;
-	u32 trig;
+	u32 trig, len, maxlen;
+	void *buf;
 
 	ret = rtl_snand_xfer_head(snand, cs, op);
 	if (ret)
 		goto out_deselect;
 
 	if (op->data.dir == SPI_MEM_DATA_IN) {
+		maxlen = 2080;
+		buf = op->data.buf.in;
 		dir = DMA_FROM_DEVICE;
 		trig = 0;
 	} else if (op->data.dir == SPI_MEM_DATA_OUT) {
+		maxlen = 520;
+		buf = op->data.buf.out;
 		dir = DMA_TO_DEVICE;
 		trig = 1;
 	} else {
@@ -251,7 +257,7 @@  static int rtl_snand_dma_xfer(struct rtl_snand *snand, int cs, const struct spi_
 		goto out_deselect;
 	}
 
-	buf_dma = dma_map_single(snand->dev, op->data.buf.in, op->data.nbytes, dir);
+	buf_dma = dma_map_single(snand->dev, buf, op->data.nbytes, dir);
 	ret = dma_mapping_error(snand->dev, buf_dma);
 	if (ret)
 		goto out_deselect;
@@ -264,26 +270,37 @@  static int rtl_snand_dma_xfer(struct rtl_snand *snand, int cs, const struct spi_
 	if (ret)
 		goto out_unmap;
 
-	reinit_completion(&snand->comp);
+	pos = 0;
+	len = op->data.nbytes;
 
-	ret = regmap_write(snand->regmap, SNAFDRSAR, buf_dma);
-	if (ret)
-		goto out_disable_int;
+	while (pos < len) {
+		nbytes = len - pos;
+		if (nbytes > maxlen)
+			nbytes = maxlen;
 
-	ret = regmap_write(snand->regmap, SNAFDLR,
-			   CMR_WID(op->data.buswidth) | (op->data.nbytes & 0xffff));
-	if (ret)
-		goto out_disable_int;
+		reinit_completion(&snand->comp);
 
-	ret = regmap_write(snand->regmap, SNAFDTR, trig);
-	if (ret)
-		goto out_disable_int;
+		ret = regmap_write(snand->regmap, SNAFDRSAR, buf_dma + pos);
+		if (ret)
+			goto out_disable_int;
 
-	if (!wait_for_completion_timeout(&snand->comp, usecs_to_jiffies(20000)))
-		ret = -ETIMEDOUT;
+		pos += nbytes;
 
-	if (ret)
-		goto out_disable_int;
+		ret = regmap_write(snand->regmap, SNAFDLR,
+				CMR_WID(op->data.buswidth) | nbytes);
+		if (ret)
+			goto out_disable_int;
+
+		ret = regmap_write(snand->regmap, SNAFDTR, trig);
+		if (ret)
+			goto out_disable_int;
+
+		if (!wait_for_completion_timeout(&snand->comp, usecs_to_jiffies(20000)))
+			ret = -ETIMEDOUT;
+
+		if (ret)
+			goto out_disable_int;
+	}
 
 out_disable_int:
 	regmap_update_bits(snand->regmap, SNAFCFR, SNAFCFR_DMA_IE, 0);