Re: [PATCH V6 1/3] mmc: mmci: add hardware busy timeout feature

From: Ludovic BARRE
Date: Fri Oct 04 2019 - 08:59:31 EST

hi Ulf

Le 10/4/19 Ã 8:20 AM, Ulf Hansson a ÃcritÂ:
On Fri, 4 Oct 2019 at 08:12, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:

On Thu, 5 Sep 2019 at 14:21, Ludovic Barre <ludovic.Barre@xxxxxx> wrote:

From: Ludovic Barre <ludovic.barre@xxxxxx>

In some variants, the data timer starts and decrements
when the DPSM enters in Wait_R or Busy state
(while data transfer or MMC_RSP_BUSY), and generates a
data timeout error if the counter reach 0.



-Define max_busy_timeout (in ms) according to clock.
-Set data timer register if the command has rsp_busy flag.
If busy_timeout is not defined by framework, the busy
length after Data Burst is defined as 1 second
(refer: 4.6.2.2 Write of sd specification part1 v6-0).

How about re-phrasing this as below:

-----
In the stm32_sdmmc variant, the datatimer is active not only during
data transfers with the DPSM, but also while waiting for the busyend
IRQs from commands having the MMC_RSP_BUSY flag set. This leads to an
incorrect IRQ being raised to signal MCI_DATATIMEOUT error, which
simply breaks the behaviour.

Address this by updating the datatimer value before sending a command
having the MMC_RSP_BUSY flag set. To inform the mmc core about the
maximum supported busy timeout, which also depends on the current
clock rate, set ->max_busy_timeout (in ms).

Thanks for the re-phrasing.

-----

Regarding the busy_timeout, the core should really assign it a value
for all commands having the RSP_BUSY flag set. However, I realize the
core needs to be improved to cover all these cases - and I am looking
at that, but not there yet.

I would also suggest to use a greater value than 1s, as that seems a
bit low for the "undefined" case. Perhaps use the max_busy_timeout,
which would be nice a simple or 10s, which I think is used by some
other drivers.

OK, I will set 10s, the max_busy_timeout could be very long for small frequencies (example, 25Mhz => 171s).


-Add MCI_DATATIMEOUT error management in mmci_cmd_irq.

Signed-off-by: Ludovic Barre <ludovic.barre@xxxxxx>
---
drivers/mmc/host/mmci.c | 42 ++++++++++++++++++++++++++++++++++++-----
drivers/mmc/host/mmci.h | 3 +++
2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index c37e70dbe250..c30319255dc2 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -1075,6 +1075,7 @@ static void
mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
{
void __iomem *base = host->base;
+ unsigned long long clks;

dev_dbg(mmc_dev(host->mmc), "op %02x arg %08x flags %08x\n",
cmd->opcode, cmd->arg, cmd->flags);
@@ -1097,6 +1098,16 @@ mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
else
c |= host->variant->cmdreg_srsp;
}
+
+ if (host->variant->busy_timeout && cmd->flags & MMC_RSP_BUSY) {
+ if (!cmd->busy_timeout)
+ cmd->busy_timeout = 1000;
+
+ clks = (unsigned long long)cmd->busy_timeout * host->cclk;
+ do_div(clks, MSEC_PER_SEC);
+ writel_relaxed(clks, host->base + MMCIDATATIMER);
+ }
+
if (/*interrupt*/0)
c |= MCI_CPSM_INTERRUPT;

@@ -1201,6 +1212,7 @@ static void
mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
unsigned int status)
{
+ u32 err_msk = MCI_CMDCRCFAIL | MCI_CMDTIMEOUT;
void __iomem *base = host->base;
bool sbc, busy_resp;

@@ -1215,8 +1227,11 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
* handling. Note that we tag on any latent IRQs postponed
* due to waiting for busy status.
*/
- if (!((status|host->busy_status) &
- (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT|MCI_CMDSENT|MCI_CMDRESPEND)))
+ if (host->variant->busy_timeout && busy_resp)
+ err_msk |= MCI_DATATIMEOUT;
+
+ if (!((status | host->busy_status) &
+ (err_msk | MCI_CMDSENT | MCI_CMDRESPEND)))
return;

/* Handle busy detection on DAT0 if the variant supports it. */
@@ -1235,8 +1250,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
* while, to allow it to be set, but tests indicates that it
* isn't needed.
*/
- if (!host->busy_status &&
- !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) &&
+ if (!host->busy_status && !(status & err_msk) &&
(readl(base + MMCISTATUS) & host->variant->busy_detect_flag)) {

writel(readl(base + MMCIMASK0) |
@@ -1290,6 +1304,9 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
cmd->error = -ETIMEDOUT;
} else if (status & MCI_CMDCRCFAIL && cmd->flags & MMC_RSP_CRC) {
cmd->error = -EILSEQ;
+ } else if (host->variant->busy_timeout && busy_resp &&
+ status & MCI_DATATIMEOUT) {
+ cmd->error = -ETIMEDOUT;

It's not really clear to me what happens with the busy detection
status bit (variant->busy_detect_flag), in case a MCI_DATATIMEOUT IRQ
is raised, while also having host->busy_status set (waiting for
busyend).

By looking at the code a few lines above this, we may do a "return;"
while waiting for the busyend IRQ even if MCI_DATATIMEOUT also is
raised, potentially losing that from being caught. Is that really
correct?

A second thought. That "return;" is to manage the busyend IRQ being
raised of the first edge due to broken HW. So I guess, this isn't an
issue for stm32_sdmmc variant after all?

I have a look at the next patches in the series..

you're referring to "return" of ?
if (host->busy_status &&
(status & host->variant->busy_detect_flag)) {
writel(host->variant->busy_detect_mask,
host->base + MMCICLEAR);
return;
}

For stm32 variant (in patch 3/3): the "busy completion" is
released immediately if there is an error or busyd0end,
and cleans: irq, busyd0end mask, busy_status variable.

I could add similar action in patch 2/3 function: "ux500_busy_complete"

static bool ux500_busy_complete(struct mmci_host *host, u32 status, u32 err_msk)
{
void __iomem *base = host->base;

if (status & err_msk)
goto complete;
...
complete:
/* specific action to clean busy detection, irq, mask, busy_status */
}

what do you think about it?


[...]

Kind regards
Uffe