Dear Miquel,
Thank you for your reply.
On 2024/10/9 下午 04:04, Miquel Raynal wrote:
Hi Hui-Ping,
+ return 0;
+ }
+
+ ma35_nand_dmac_init(nand);
+
+ writel(mtd->oobsize, nand->regs + MA35_NFI_REG_NANDRACTL);
+
+ /* setup and start DMA using dma_addr */
+ dma_addr = dma_map_single(nand->dev, (void *)addr, len, DMA_FROM_DEVICE);
+ ret = dma_mapping_error(nand->dev, dma_addr);
+ if (ret) {
+ dev_err(nand->dev, "dma mapping error\n");
+ return -EINVAL;
+ }
+
+ writel((unsigned long)dma_addr, nand->regs + MA35_NFI_REG_DMASA);
Please enforce a dma mask of 32 (even though it might be the fault).
I will change it to dma_addr & 0xffffffff.
That's not what I mean, I believe you should use the dma API to ask for
a mapping within the accessible 32-bit address range. The
dma_mapping_error() check should return an error if that's not the
case. Then you can safely write the value.
Here is my misunderstanding: just fill in the dma_addr directly,
no type conversion is needed. I have already tested it.
FYI, it only works because the default DMA mask for your device is gonna
be 32 bits. If the reality (what your peripheral DMA can do) was
different than this, you would have to set a different mask explicitly
to make sure the dma-mapping step would not provide buffers which are
out of reach.
Sure, I will keep that in mind. However, due to the memory architecture
of the MA35,
which is designed for a maximum of 4GB, there won’t be any situation
exceeding 32 bits.
Thank you.
Thanks,
Miquèl
Best regards,
Hui-Ping Chen
