On 11/28/13 15:06, Adrian Hunter wrote:
On 28/11/13 13:48, Vladimir Zapolskiy wrote:
On 11/28/13 09:12, Adrian Hunter wrote:
On 27/11/13 16:57, Vladimir Zapolskiy wrote:
On 11/27/13 10:21, Adrian Hunter wrote:
On 26/11/13 18:33, Vladimir Zapolskiy wrote:
On 11/26/13 11:04, Adrian Hunter wrote:
On 22/11/13 17:21, Vladimir Zapolskiy wrote:
On 22.11.2013 16:04, Adrian Hunter wrote:
On 22/11/13 15:50, Vladimir Zapolskiy wrote:
On 22.11.2013 14:04, Adrian Hunter wrote:
On 22/11/13 14:24, Vladimir Zapolskiy wrote:
On 22.11.2013 12:38, Adrian Hunter wrote:
On 21/11/13 17:07, Vladimir Zapolskiy wrote:
JEDEC specification defines quite high erase timeout value for
300ms
multiplied by erase group number, and SD Host Controller
specification
data line timeout may be much less, e.g. 2^13 / 52MHz ~ 160us.
From block layer and MMC perfromance perspective it is
desirable
that
millions of erase groups are discarded at once, so there is no
much
sense to limit maximum erase timeout by data line timeout, if a
controller handles correctly erase operation without indication of
data line timeout.
Would you explain that some more. Do you mean that:
a) it does not have a timeout
JEDEC defines a timeout on erase/trim operations, also in
drivers/mmc/core/core.c
there is a reasonable enough 10 minutes limitation for discard
operations.
b) it has a timeout which is less than the timeout
specified
by the
standard but the operation nevertheless completes
SDHC data line timeout is enormously less than erase group timeout,
and
trivial testing shows that those two timeouts are independent,
probably
except some particular cases of controllers not known before commits
58d1246db3 and e056a1b5b.
According to the currently implemented logic, mmc_do_erase()
commonly is
instructed to discard 1-2 erase groups at maximum, however it tends
to be
capable to successfully discard millions of erase groups at once
ignoring
that SDHC data line timeout limitation.
You seem to be trying to say that the SDHCI spec. says that the host
controller does not timeout erase operations or uses a different
timeout
than the one programmed in the "Timeout Control Register". Where is
that is
the SDHCI spec?
According to the spec a host controller timeouts erase operations
like any
other R1B command.
So in your opinion, should there be SDHCI_QUIRK_BROKEN_TIMEOUT_VAL
instead
of the new quirk?
I don't understand how SDHCI_QUIRK_BROKEN_TIMEOUT_VAL would help. It
just
sets the timeout to maximum but max_discard_to is the maximum timeout.
Here I meant to do something like:
if (host->quirks& SDHCI_QUIRK_BROKEN_TIMEOUT_VAL)
mmc->max_discard_to = 0;
Again I'm not sure that this applies well to all
SDHCI_QUIRK_BROKEN_TIMEOUT_VAL
controllers, therefore a new quirk might be better.
As I understand it you don't want to limit the discard size, either
because
your controller does not timeout, or because you are happy that the
maximum
timeout is enough for your users and their use-cases.
If that is the case then the original patch just needs the quirk the
other
way around. i.e.
if (host->quirks2& SDHCI_QUIRK2_NO_DISCARD_LIMIT)
mmc->max_discard_to = 0;
else
mmc->max_discard_to = (1<< 27) / host->timeout_clk;
This suits me fine, thanks for review, and I'll resend a change based on
this.
Also I'd like to pay your attention to (1<< 27) / host->timeout_clk
part of
calculation, following the spec it might be better to account the actual
value of Data Timeout Counter, otherwise a controller may get
unintentional
Data Timeout Error pretty soon. Please correct me, if I'm mistaken here.
Not sure what you mean. max_discard_to is the maximum timeout (in
milliseconds) that the host controller supports. The intent is to limit
erase operations to ones that have a timeout that is less than or
equal to
that.
That's clear. But it's not obvious why do you prefer (1<< 27) numerator
instead
of secure (1<< 13) or (1<< (13 + sdhci_readl(host,
SDHCI_TIMEOUT_CONTROL))).
The maximum value of "Data Timeout Counter Value" in "Timeout Control
Register" is 14 and the maximum timeout is therefore (1<< 27).
So, from this perspective I assume this is a potential theoretical maximum
timeout for a controller, which may be 16384 times more than the maximum
guaranteed timeout before getting a DAT timeout. Why is the theoretical
maximum
Where do you get the notion of "maximum guaranteed timeout"? The timeout is
what is programmed in "Data Timeout Counter Value".
And exactly this "Data Timeout Counter Value" is not used in your code to
predict controller's data line timeout.
supposed to be used in calculations of a guaranteed discard operation
timeout
instead of promised DAT timeout by a controller?
What is "promised DAT timeout"?
This is a timeout with respect to "Data Timeout Counter Value".
According to your words max_discard_to is the maximum timeout that the host
controller supports, but such a parameter is useless, because nobody sets
the host controller SDHCI_TIMEOUT_CONTROL register to maximum supported value,
sdhci_prepare_data() -> sdhci_calc_timeout() sets the timeout based on what
the upper layers specify, up to and including the maximum value.
So what max_discard_to does is to limit the erase size so that when
sdhci_calc_timeout() is called it won't exceed the maximum.
Now the idea is clear, thank you.
so there is a probability that you greatly overestimate Data Timeout value,
and therefore block layer or other subsystem can't rely on it. Please correct
me here.
Currently, the limit gets applied by the block layer before the mmc
layer is
involved so there is no possibility to take the actual timeout into
account.
However if you have erase_group_def set, then it won't make any
difference
i.e. the limit will be the same.
Potentially the change may break some of the SDHCs on discard of
mmc,
and for backward compatibility a new quirk is introduced, which
is NOT
set by default.
It sounds to me that what you want to do is not standard so the
quirk
should
be the other way around.
Please take a look at commits 58d1246db3 and e056a1b5b, I'd be
glad, if
you
could elaborate to which "some host controllers" the quirk in my
definition
applies, I believe all other host controllers present at that
time in
drivers/mmc/host/* are capable to discard without introduced
limitation.
"some host controllers" == SDHCI i.e. to all of the ones you are
applying
the change.
Signed-off-by: Vladimir Zapolskiy<vladimir_zapolskiy@xxxxxxxxxx>
Reported-by: Ed Sutter<ed.sutter@xxxxxxxxxxxxxxxxxx>
Cc: Chris Ball<cjb@xxxxxxxxxx>
Cc: Adrian Hunter<adrian.hunter@xxxxxxxxx>
---
drivers/mmc/host/sdhci.c | 5 ++++-
include/linux/mmc/sdhci.h | 1 +
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index bd8a098..b1fdddb 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2930,7 +2930,10 @@ int sdhci_add_host(struct sdhci_host *host)
if (host->quirks&
SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)
host->timeout_clk = mmc->f_max / 1000;
- mmc->max_discard_to = (1<< 27) / host->timeout_clk;
+ if (host->quirks2&
SDHCI_QUIRK2_DATA_TIMEOUT_ON_DISCARD)
+ mmc->max_discard_to = (1<< 27) / host->timeout_clk;
+ else
+ mmc->max_discard_to = 0;
mmc->caps |= MMC_CAP_SDIO_IRQ | MMC_CAP_ERASE |
MMC_CAP_CMD23;
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index 3e781b8..e7f6bd2 100644
--- a/include/linux/mmc/sdhci.h
+++ b/include/linux/mmc/sdhci.h
@@ -98,6 +98,7 @@ struct sdhci_host {
#define SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON (1<<4)
/* Controller has a non-standard host control register */
#define SDHCI_QUIRK2_BROKEN_HOST_CONTROL (1<<5)
+#define SDHCI_QUIRK2_DATA_TIMEOUT_ON_DISCARD (1<<6)
int irq; /* Device IRQ */
void __iomem *ioaddr; /* Mapped address */
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