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mtd: nand/fsmc: Access the NAND device word by word whenever possible

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The default way of accessing nand device is using the nand width. This means
that 8bit devices are using u8 * and 16bit devices are accessed using u16 *.

This results in a non-optimal performance since the FSMC is designed to
translate the normal word accesses into device width based accesses. This patch
implements read_buf and write_buf callbacks using word by word accesses.

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Vipin Kumar 2012-03-14 11:47:17 +05:30 committed by David Woodhouse
parent 712c4add03
commit 604e75444f
2 changed files with 61 additions and 0 deletions
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55
drivers/mtd/nand/fsmc_nand.c
View File

@ -523,6 +523,52 @@ static int count_written_bits(uint8_t *buff, int size, int max_bits)
return written_bits;
}
/*
* fsmc_write_buf - write buffer to chip
* @mtd: MTD device structure
* @buf: data buffer
* @len: number of bytes to write
*/
static void fsmc_write_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
{
int i;
struct nand_chip *chip = mtd->priv;
if (IS_ALIGNED((uint32_t)buf, sizeof(uint32_t)) &&
IS_ALIGNED(len, sizeof(uint32_t))) {
uint32_t *p = (uint32_t *)buf;
len = len >> 2;
for (i = 0; i < len; i++)
writel(p[i], chip->IO_ADDR_W);
} else {
for (i = 0; i < len; i++)
writeb(buf[i], chip->IO_ADDR_W);
}
}
/*
* fsmc_read_buf - read chip data into buffer
* @mtd: MTD device structure
* @buf: buffer to store date
* @len: number of bytes to read
*/
static void fsmc_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
int i;
struct nand_chip *chip = mtd->priv;
if (IS_ALIGNED((uint32_t)buf, sizeof(uint32_t)) &&
IS_ALIGNED(len, sizeof(uint32_t))) {
uint32_t *p = (uint32_t *)buf;
len = len >> 2;
for (i = 0; i < len; i++)
p[i] = readl(chip->IO_ADDR_R);
} else {
for (i = 0; i < len; i++)
buf[i] = readb(chip->IO_ADDR_R);
}
}
/*
* fsmc_read_page_hwecc
* @mtd: mtd info structure
@ -825,6 +871,15 @@ static int __init fsmc_nand_probe(struct platform_device *pdev)
if (pdata->width == FSMC_NAND_BW16)
nand->options |= NAND_BUSWIDTH_16;
/*
* use customized (word by word) version of read_buf, write_buf if
* access_with_dev_width is reset supported
*/
if (pdata->mode == USE_WORD_ACCESS) {
nand->read_buf = fsmc_read_buf;
nand->write_buf = fsmc_write_buf;
}
fsmc_nand_setup(regs, host->bank, nand->options & NAND_BUSWIDTH_16,
host->dev_timings);

6
include/linux/mtd/fsmc.h
View File

@ -141,6 +141,11 @@ struct fsmc_nand_timings {
uint8_t tset;
};
enum access_mode {
USE_DMA_ACCESS = 1,
USE_WORD_ACCESS,
};
/**
* fsmc_nand_platform_data - platform specific NAND controller config
* @partitions: partition table for the platform, use a default fallback
@ -164,6 +169,7 @@ struct fsmc_nand_platform_data {
/* CLE, ALE offsets */
unsigned long cle_off;
unsigned long ale_off;
enum access_mode mode;
void (*select_bank)(uint32_t bank, uint32_t busw);
};