Messages in this thread |  | | Date | Wed, 29 Jun 2011 15:09:59 +0200 | | From | Nicolas Ferre <> | | Subject | Re: [RFC PATCH] MTD: atmel_nand: optimize read/write buffer functions |
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Le 28/06/2011 16:59, Russell King - ARM Linux : > On Tue, Jun 28, 2011 at 01:10:43PM +0200, Uwe Kleine-König wrote: >>> @@ -265,33 +234,53 @@ err_buf: >>> static void atmel_read_buf(struct mtd_info *mtd, u8 *buf, int len) >>> { >>> struct nand_chip *chip = mtd->priv; >>> - struct atmel_nand_host *host = chip->priv; >>> + u32 align; >>> + u8 *pbuf; >>> >>> if (use_dma && len > mtd->oobsize) >>> /* only use DMA for bigger than oob size: better performances */ >>> if (atmel_nand_dma_op(mtd, buf, len, 1) == 0) >>> return; >>> >>> - if (host->board->bus_width_16) >>> - atmel_read_buf16(mtd, buf, len); >>> - else >>> - atmel_read_buf8(mtd, buf, len); >>> + /* if no DMA operation possible, use PIO */ >>> + pbuf = buf; >>> + align = 0x03 & ((unsigned)pbuf); >>> + >>> + if (align) { >>> + u32 align_len = 4 - align; >>> + >>> + /* non aligned buffer: re-align to next word boundary */ >>> + ioread8_rep(chip->IO_ADDR_R, pbuf, align_len); >>> + pbuf += align_len; >>> + len -= align_len; >>> + } >>> + memcpy((void *)pbuf, chip->IO_ADDR_R, len); >> I think you don't need to cast to (void *). I think you need to cast the >> 2nd parameter instead because sparse don't like you passing an void >> __iomem *. >> Is it correct to read from chip->IO_ADDR_R, don't you need >> chip->IO_ADDR_R + align_len? Taking this into account, does it really >> help to align pbuf? > > I think you need to read Documentation/bus-virt-phys-mapping.txt, > particularly the part after "NOTE NOTE NOTE". > > Dereferencing ioremap'd memory is not permitted. That includes passing > it to memcpy. Even with a cast.
So that means that I should use memcpy_fromio() even if the code if far less optimized.
Shouldn't I re-implement some kind of IO copying function to deal with this IO memory so that I could take advantage of 8 words bursts?
Best regards, -- Nicolas Ferre
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