On 21/05/12 14:19, Dong, Chuanxiao wrote:
>
>
>> -----Original Message-----
>> From: Hunter, Adrian
>> Sent: Monday, May 21, 2012 7:06 PM
>> To: Dong, Chuanxiao
>> Cc: linux-mmc@xxxxxxxxxxxxxxx; cjb@xxxxxxxxxx
>> Subject: Re: [PATCH]mmc: core: not to --qty when calculate timeout for
>> SECURE_ERASE
>>
>> On 13/04/12 07:19, Chuanxiao Dong wrote:
>>> --qty when calculating erase timeout for trim/erase & secure
>>> trim/erase can prevent the erase range crossing qty+1 erase groups,
>>> which made the final timeout value is too large for the host.
>>>
>>> When operate SECURE_ERASE, driver needs the erase range is aligned
>>> with erase size, otherwise do nothing and return an error. That is to
>>> say it is not necessary for SECURE_ERASE to --qty since it will never
>>> cross an erase group.
>>>
>>> Signed-off-by: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx>
>>> ---
>>> drivers/mmc/core/core.c | 9 ++++++++-
>>> 1 files changed, 8 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index
>>> e541efb..b5a393a 100644
>>> --- a/drivers/mmc/core/core.c
>>> +++ b/drivers/mmc/core/core.c
>>> @@ -1761,7 +1761,7 @@ static unsigned int mmc_do_calc_max_discard(struct
>> mmc_card *card,
>>> if (!qty)
>>> return 0;
>>>
>>> - if (qty == 1)
>>> + if (qty == 1 && arg != MMC_SECURE_ERASE_ARG)
>>> return 1;
>>
>> arg is never MMC_SECURE_ERASE_ARG
>>
>>>
>>> /* Convert qty to sectors */
>>> @@ -1772,6 +1772,13 @@ static unsigned int mmc_do_calc_max_discard(struct
>> mmc_card *card,
>>> else
>>> max_discard = --qty * card->erase_size;
>>>
>>> + /*
>>> + * since SECURE_ERASE is erase group aligned, otherwise
>>> + * it cannot be erased in secure purpose, needn't --qty
>>> + */
>>> + if (arg == MMC_SECURE_ERASE_ARG)
>>> + max_discard += card->erase_size;
>>> +
>>> return max_discard;
>>> }
>>>
>>
>> What about:
>>
>> From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Date: Mon, 21 May 2012 13:32:42 +0300
>> Subject: [PATCH] mmc: core: fix max_discard calculation
>>
>> The maximum discard calculation was unnecessarily pessimistic in the case of
>> erasing entire erase groups. In that case, the quantity does not need to be
>> decreased by 1 to allow for misalignment because the erasure is always aligned to
>> whole erase groups.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> ---
>> drivers/mmc/core/core.c | 22 +++++++++++++++++-----
>> 1 files changed, 17 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index
>> 0b6141d..36bfdce 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -1742,7 +1742,7 @@ static unsigned int mmc_do_calc_max_discard(struct
>> mmc_card *card, {
>> struct mmc_host *host = card->host;
>> unsigned int max_discard, x, y, qty = 0, max_qty, timeout;
>> - unsigned int last_timeout = 0;
>> + unsigned int last_timeout = 0, aligned_qty;
>>
>> if (card->erase_shift)
>> max_qty = UINT_MAX >> card->erase_shift; @@ -1769,16 +1769,28 @@
>> static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
>> if (!qty)
>> return 0;
>>
>> - if (qty == 1)
>> - return 1;
>> + if (arg & MMC_TRIM_ARGS) {
>> + /*
>> + * The requested number of sectors may not be aligned to an
>> + * erase group, so we have to decrease the quantity by 1 (unless
>> + * it is 1) e.g. trimming 2 sectors could cause 2 erase groups
>> + * to be affected even though 2 sectors is less than the size of
>> + * 1 erase group.
>> + */
>> + if (qty == 1)
>> + return 1;
>> + aligned_qty = qty - 1;
>> + } else {
>> + aligned_qty = qty;
>> + }
>>
>> /* Convert qty to sectors */
>> if (card->erase_shift)
>> - max_discard = --qty << card->erase_shift;
>> + max_discard = aligned_qty << card->erase_shift;
>> else if (mmc_card_sd(card))
>> max_discard = qty;
>> else
>> - max_discard = --qty * card->erase_size;
>> + max_discard = aligned_qty * card->erase_size;
>>
>> return max_discard;
>> }
>
> Hi Hunter,
> Your patch looks good to me.
>
> Since you also mentioned that the arg will never be MMC_SECURE_ERASE_ARG, I want to know why not calculate erase size for secure trim/erase operations? As specification said, secure trim/erase operations has different timeout value with trim/erase.
There are 2 problems. First, there is only 1 value for maximum discard
whether secure or not. Secondly, the timeout for secure erase can be so
great that any quantity exceeds the maximum timeout.
>
> Thanks
> Chuanxiao
>
>
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