Re: mmc_core: question on mmc_do_erase function

[Adrian Hunter <adrian.hunter@nokia.com>]

On 12/10/10 16:11, Dong, Chuanxiao wrote:
> Hi adrian
>
> I got some questions about MMC driver erase function. Help you can
> give me some suggestion. My host controller is a kind of SDHCI host
> controller. And testing below code by using HD micro SD card.
> +	memset(&cmd, 0, sizeof(struct mmc_command));
> +	cmd.opcode = MMC_ERASE;
> +	cmd.arg = arg;
> +	cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
> +	mmc_set_erase_timeout(card,&cmd, arg, qty);
> +	err = mmc_wait_for_cmd(card->host,&cmd, 0);
> +	if (err) {
> +		printk(KERN_ERR "mmc_erase: erase error %d, status %#x\n",
> +		       err, cmd.resp[0]);
> +		err = -EIO;
> +		goto out;
> +	}
> As MMC 4.4 standard said, CMD38 need R1B response. So when SDHCI host
> controller got a SDHCI_INT_RESPONSE interrupt, driver will ignore
> this and keep on waiting for a SDHCI_INT_DATA_END interrupt to finish
> MMC_ERASE command. Then I got problems....My host controller will got
> a DATA_TIMEOUT interrupt if host controller cannot generate any
> interrupt during its waiting time, unfortunately the max waiting time
> for my SDHCI host controller is 5s.

I don't know SDHCI.  Can you disable the timeout altogether and use a
timer?

> So if any ERASE operation need
> more than 5s seconds to finish, my controller will not finish the
> ERASE operation and only generate a DATA_TIMEOUT interrupt. The ERASE
> will be failed. Another, MMC driver also has a 10s timer to keep
> watch over the interrupt, if ERASE operation need more than 10s to
> finish, this timer also can report a TIMEOUT error. I think
> cmd->erase_timeout can help to set the timer expires, but how to deal
> with this issue for SDHCI host controller? How about split ERASE
> groups to be smaller ones?

Where is the erase coming from?  A file system?  The discard ioctl?

It is possible to set a maximum size for the discard but it pays
no attention to alignment, so you can get very sub-optimal erases.

>
> +	if (mmc_host_is_spi(card->host))
> +		goto out;
> +
> +	do {
> +		memset(&cmd, 0, sizeof(struct mmc_command));
> +		cmd.opcode = MMC_SEND_STATUS;
> +		cmd.arg = card->rca<<  16;
> +		cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
> +		/* Do not retry else we can't see errors */
> +		err = mmc_wait_for_cmd(card->host,&cmd, 0);
> +		if (err || (cmd.resp[0]&  0xFDF92000)) {
> +			printk(KERN_ERR "error %d requesting status %#x\n",
> +				err, cmd.resp[0]);
> +			err = -EIO;
> +			goto out;
> +		}
> +	} while (!(cmd.resp[0]&  R1_READY_FOR_DATA) ||
> +		 R1_CURRENT_STATE(cmd.resp[0]) == 7);
> +out:
> +	return err;
> +}
> And can this code guarantee the card will finish the ERASE operation?
> If it can, what about send CMD38 with R1 response?(although doing
> this is against with MMC 4.4 standard....)
>
> Best Regards
> Chuanxiao Dong
>
>