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Message-ID: <CAPDyKFoxMtMjzc4nXnhOvribUBAfzNjm+LbruSVkXgQW_bxgUA@mail.gmail.com>
Date: Tue, 19 Jul 2016 13:57:46 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Baolin Wang <baolin.wang@...aro.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
Russell King <rmk+kernel@....linux.org.uk>,
Shawn Lin <shawn.lin@...k-chips.com>,
Doug Anderson <dianders@...omium.org>,
Heiko Stübner <heiko@...ech.de>,
linux-mmc <linux-mmc@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Mark Brown <broonie@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [RESEND RFC v2] mmc: Change the max discard sectors and erase
response if mmc host supports busy signalling
On 13 June 2016 at 10:54, Baolin Wang <baolin.wang@...aro.org> wrote:
> When mmc host HW supports busy signalling (using R1B as response), We
> shouldn't use 'host->max_busy_timeout' as the limitation when deciding
> the max discard sectors that we tell the generic BLOCK layer about.
> Instead, we should pick one preferred erase size as the max discard
> sectors.
>
> If the host controller supports busy signalling and the timeout for
> the erase operation does not exceed the max_busy_timeout, we should
> use R1B response. Or we need to prevent the host from doing hw busy
> detection, which is done by converting to a R1 response instead.
>
> Changes since v1:
> - Remove the 'MMC_CAP_WAIT_WHILE_BUSY' flag checking when deciding
> the max discard sectors.
>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> ---
> drivers/mmc/core/core.c | 47 +++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 39 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 8b4dfd4..edd43b1 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2060,7 +2060,7 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
> unsigned int to, unsigned int arg)
> {
> struct mmc_command cmd = {0};
> - unsigned int qty = 0;
> + unsigned int qty = 0, busy_timeout = 0;
> unsigned long timeout;
> int err;
>
> @@ -2128,8 +2128,23 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
> 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;
> - cmd.busy_timeout = mmc_erase_timeout(card, arg, qty);
> + busy_timeout = mmc_erase_timeout(card, arg, qty);
> + /*
> + * If the host controller supports busy signalling and the timeout for
> + * the erase operation does not exceed the max_busy_timeout, we should
> + * use R1B response. Or we need to prevent the host from doing hw busy
> + * detection, which is done by converting to a R1 response instead.
> + */
> + if ((card->host->max_busy_timeout &&
> + busy_timeout > card->host->max_busy_timeout) ||
> + !(card->host->caps & MMC_CAP_WAIT_WHILE_BUSY)) {
sdhci uses the max_busy_timeout, but doesn't always use MMC_CAP_WAIT_WHILE_BUSY.
I have probably asked Adrian about this before, but right now I can't
recall why this is the case.
Anyway, I don't think we need to check MMC_CAP_WAIT_WHILE_BUSY at this point.
> + cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
> + cmd.busy_timeout = 0;
> + } else {
> + cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
> + cmd.busy_timeout = busy_timeout;
> + }
> +
> err = mmc_wait_for_cmd(card->host, &cmd, 0);
> if (err) {
> pr_err("mmc_erase: erase error %d, status %#x\n",
You also need to fix the loop for polling with CMD13 to get the card
status. In case of when R1B+MMC_CAP_WAIT_WHILE_BUSY is used, the
polling shall be avoided.
Moreover, the polling loop doesn't care about the earlier used
calculated erase timeout, but instead defaults to the
MMC_CORE_TIMEOUT_MS, this is wrong.
Finally, perhaps as an improvement step; I think we shall make use of
the host's ->card_busy() callback if implemented and when
R1B+MMC_CAP_WAIT_WHILE_BUSY isn't used. This in favour of issuing
CMD13 in the loop.
You can see the sequence in __mmc_switch(), we should apply this to
the erase case as well. Perhaps we can even split up some of the code
in __mmc_switch() to allow it to re-used for the erase case as well!?
> @@ -2321,23 +2336,39 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
> unsigned int arg)
> {
> struct mmc_host *host = card->host;
> - unsigned int max_discard, x, y, qty = 0, max_qty, timeout;
> + unsigned int max_discard, x, y, qty = 0, max_qty, min_qty, timeout;
> unsigned int last_timeout = 0;
>
> - if (card->erase_shift)
> + if (card->erase_shift) {
> max_qty = UINT_MAX >> card->erase_shift;
> - else if (mmc_card_sd(card))
> + min_qty = card->pref_erase >> card->erase_shift;
> + } else if (mmc_card_sd(card)) {
> max_qty = UINT_MAX;
> - else
> + min_qty = card->pref_erase;
> + } else {
> max_qty = UINT_MAX / card->erase_size;
> + min_qty = card->pref_erase / card->erase_size;
> + }
>
> /* Find the largest qty with an OK timeout */
This comment needs to be updated.
> do {
> y = 0;
> for (x = 1; x && x <= max_qty && max_qty - x >= qty; x <<= 1) {
> timeout = mmc_erase_timeout(card, arg, qty + x);
> - if (timeout > host->max_busy_timeout)
> + /*
> + * We should not only use 'host->max_busy_timeout' as
> + * the limitation when deciding the max discard sectors.
> + * We should set a balance value to improve the erase
> + * speed, and it can not get too long timeout at the
> + * same time.
I am not really sure I understand this comment. Could you try to
elaborate on what value that will be picked when the max_busy_timeout
isn't just as the limiter.
> + *
> + * Here we set 'card->pref_erase' as the minimal discard
> + * sectors when deciding the max discard sectors.
> + */
> + if (qty + x > min_qty &&
> + timeout > host->max_busy_timeout)
> break;
> +
> if (timeout < last_timeout)
> break;
> last_timeout = timeout;
> --
> 1.7.9.5
>
Again, sorry for the delay in response!
Kind regards
Uffe
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