Subject: [PATCH v2 4/4] mtd: atmel_nand: enable Nand Flash Controller (NFC) write via sram

From: [email-masked] (Josh Wu)
Date: Mon, 27 May 2013 18:01:42 +0800

On 5/25/2013 4:11 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 17:51 Fri 17 May     , Josh Wu wrote:
>> This patch enable writing nand flash via NFC SRAM. It will minimize the CPU
>> overhead. The SRAM write only support ECC_NONE and ECC_HW with PMECC.
>>
>> This driver has been tested on SAMA5D3X-EK with JFFS2, YAFFS2, UBIFS and
>> mtd-utils.
>>
>> Here is part of mtd_speedtest (writing test) result, compare with non-NFC
>> writing, it reduces %65 cpu load with loss %12 speed.
> we may want to enable only read on sram and not write as the write speed can
> be critic on some system

I will add one more option to allow user to choose to use NFC write via 
sram.

Best Regards,
Josh Wu

>
> Best Regards,
> J.
>> - commands use to test:
>>    # insmod /mnt/mtd_speedtest.ko dev=2 &
>>    # top -n 30 -d 1 | grep speedtest
>>
>> - test result:
>> =================================================
>> mtd_speedtest: MTD device: 2
>> mtd_speedtest: MTD device size 41943040, eraseblock size 131072, page size 2048, count of eraseblocks 320, pages per eraseblock 64, OOB size 64
>> mtd_speedtest: testing eraseblock write speed
>>    509   495 root     D     1164   0%   7% insmod /mnt/mtd_speedtest.ko dev=2
>>    509   495 root     D     1164   0%   8% insmod /mnt/mtd_speedtest.ko dev=2
>>    509   495 root     R     1164   0%   5% insmod /mnt/mtd_speedtest.ko dev=2
>> mtd_speedtest: eraseblock write speed is 5194 KiB/s
>> mtd_speedtest: testing page write speed
>>    509   495 root     D     1164   0%  32% insmod /mnt/mtd_speedtest.ko dev=2
>>    509   495 root     D     1164   0%  27% insmod /mnt/mtd_speedtest.ko dev=2
>>    509   495 root     D     1164   0%  25% insmod /mnt/mtd_speedtest.ko dev=2
>>    509   495 root     D     1164   0%  30% insmod /mnt/mtd_speedtest.ko dev=2
>> mtd_speedtest: page write speed is 5024 KiB/s
>>
>> Signed-off-by: Josh Wu <[email-masked]>
>> ---
>> v1 --> v2:
>>    use NAND_ECC_WRITE instead of use new defined pass to pmecc_enable().
>>    report a error if use a partial page write via nfc sram.
>>
>>   drivers/mtd/nand/atmel_nand.c |   94 +++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 90 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
>> index c10cd71..4490bd6 100644
>> --- a/drivers/mtd/nand/atmel_nand.c
>> +++ b/drivers/mtd/nand/atmel_nand.c
>> @@ -99,6 +99,7 @@ struct atmel_nfc {
>>   
>>   	/* Point to the sram bank which include readed data via NFC */
>>   	void __iomem		*data_in_sram;
>> +	bool			will_write_sram;
>>   };
>>   
>>   struct atmel_nand_host {
>> @@ -218,6 +219,16 @@ static void memcpy32_fromio(void *trg, const void __iomem  *src, size_t size)
>>   		*t++ = readl_relaxed(s++);
>>   }
>>   
>> +static void memcpy32_toio(void __iomem *trg, const void *src, int size)
>> +{
>> +	int i;
>> +	u32 __iomem *t = trg;
>> +	const u32 *s = src;
>> +
>> +	for (i = 0; i < (size >> 2); i++)
>> +		writel_relaxed(*s++, t++);
>> +}
>> +
>>   /*
>>    * Minimal-overhead PIO for data access.
>>    */
>> @@ -339,7 +350,11 @@ static int atmel_nand_dma_op(struct mtd_info *mtd, void *buf, int len,
>>   		dma_dst_addr = phys_addr;
>>   	} else {
>>   		dma_src_addr = phys_addr;
>> -		dma_dst_addr = host->io_phys;
>> +
>> +		if (host->use_nfc_sram)
>> +			dma_dst_addr = nfc_sram_phys(host);
>> +		else
>> +			dma_dst_addr = host->io_phys;
>>   	}
>>   
>>   	tx = dma_dev->device_prep_dma_memcpy(host->dma_chan, dma_dst_addr,
>> @@ -919,9 +934,10 @@ static int atmel_nand_pmecc_write_page(struct mtd_info *mtd,
>>   	int i, j;
>>   	unsigned long end_time;
>>   
>> -	pmecc_enable(host, NAND_ECC_WRITE);
>> -
>> -	chip->write_buf(mtd, (u8 *)buf, mtd->writesize);
>> +	if (!host->use_nfc_sram) {
>> +		pmecc_enable(host, NAND_ECC_WRITE);
>> +		chip->write_buf(mtd, (u8 *)buf, mtd->writesize);
>> +	}
>>   
>>   	end_time = jiffies + msecs_to_jiffies(PMECC_MAX_TIMEOUT_MS);
>>   	while ((pmecc_readl_relaxed(host->ecc, SR) & PMECC_SR_BUSY)) {
>> @@ -1805,6 +1821,8 @@ static void nfc_nand_command(struct mtd_info *mtd, unsigned int command,
>>   	case NAND_CMD_SEQIN:
>>   	case NAND_CMD_RNDIN:
>>   		nfcwr = NFCADDR_CMD_NFCWR;
>> +		if (host->nfc.will_write_sram && command == NAND_CMD_SEQIN)
>> +			dataen = NFCADDR_CMD_DATAEN;
>>   		break;
>>   	default:
>>   		break;
>> @@ -1849,6 +1867,68 @@ static void nfc_nand_command(struct mtd_info *mtd, unsigned int command,
>>   	}
>>   }
>>   
>> +static int nfc_sram_write_page(struct mtd_info *mtd, struct nand_chip *chip,
>> +			uint32_t offset, int data_len, const uint8_t *buf,
>> +			int oob_required, int page, int cached, int raw)
>> +{
>> +	int cfg, len;
>> +	int status = 0;
>> +	struct atmel_nand_host *host = chip->priv;
>> +	void __iomem *sram = host->nfc.sram_bank0 + nfc_get_sram_off(host);
>> +
>> +	/* Subpage write is not supported */
>> +	if (offset || (data_len < mtd->writesize))
>> +		return -EINVAL;
>> +
>> +	cfg = nfc_readl(host->nfc.hsmc_regs, CFG);
>> +	len = mtd->writesize;
>> +
>> +	if (unlikely(raw)) {
>> +		len += mtd->oobsize;
>> +		nfc_writel(host->nfc.hsmc_regs, CFG, cfg | ATMEL_HSMC_WSPARE);
>> +	} else
>> +		nfc_writel(host->nfc.hsmc_regs, CFG, cfg & ~ATMEL_HSMC_WSPARE);
>> +
>> +	/* Copy page data to sram that will write to nand via NFC */
>> +	if (use_dma) {
>> +		if (atmel_nand_dma_op(mtd, (void *)buf, len, 0) != 0)
>> +			/* Fall back to use cpu copy */
>> +			memcpy32_toio(sram, buf, len);
>> +	} else {
>> +		memcpy32_toio(sram, buf, len);
>> +	}
>> +
>> +	if (chip->ecc.mode == NAND_ECC_HW && host->has_pmecc)
>> +		/*
>> +		 * When use NFC sram, need set up PMECC before send
>> +		 * NAND_CMD_SEQIN command. Since when the nand command
>> +		 * is sent, nfc will do transfer from sram and nand.
>> +		 */
>> +		pmecc_enable(host, NAND_ECC_WRITE);
>> +
>> +	host->nfc.will_write_sram = true;
>> +	chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
>> +	host->nfc.will_write_sram = false;
>> +
>> +	if (likely(!raw))
>> +		/* Need to write ecc into oob */
>> +		status = chip->ecc.write_page(mtd, chip, buf, oob_required);
>> +
>> +	if (status < 0)
>> +		return status;
>> +
>> +	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
>> +	status = chip->waitfunc(mtd, chip);
>> +
>> +	if ((status & NAND_STATUS_FAIL) && (chip->errstat))
>> +		status = chip->errstat(mtd, chip, FL_WRITING, status, page);
>> +
>> +	if (status & NAND_STATUS_FAIL)
>> +		return -EIO;
>> +
>> +	return 0;
>> +}
>> +
>>   static int nfc_sram_init(struct mtd_info *mtd)
>>   {
>>   	struct nand_chip *chip = mtd->priv;
>> @@ -1887,10 +1967,16 @@ static int nfc_sram_init(struct mtd_info *mtd)
>>   
>>   	nfc_writel(host->nfc.hsmc_regs, CFG, cfg_nfc);
>>   
>> +	host->nfc.will_write_sram = false;
>>   	nfc_set_sram_bank(host, 0);
>>   
>>   	dev_info(host->dev, "Using NFC Sram\n");
>>   
>> +	/* Use Write page with NFC SRAM only for PMECC or ECC NONE. */
>> +	if ((chip->ecc.mode == NAND_ECC_HW && host->has_pmecc) ||
>> +			chip->ecc.mode == NAND_ECC_NONE)
>> +		chip->write_page = nfc_sram_write_page;
>> +
>>   	return 0;
>>   }
>>   
>> -- 
>> 1.7.9.5
>>