Re: [PATCH V5 1/3] mmc: mmci: add hardware busy timeout feature

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hi Ulf

On 8/26/19 1:39 PM, Ulf Hansson wrote:
On Tue, 13 Aug 2019 at 12:00, 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.

I don't quite follow here, sorry. Can you please try to elaborate on
the use case(s) more exactly?

For example, what happens when a data transfer has just finished (for
example when MCI_DATAEND has been received) and we are going to send a
CMD12 to stop it? In this case the CMD12 has the MMC_RSP_BUSY flag
set.


example with cmd25 (write multi block)
mmci_request
    - mmci_start_data
	set MMCIDATATIMER, MMCIDATALENGTH, MMCIMASK0
    - mmci_start_command:
	set MMCIARGUMENT, MMCICOMMAND (cmd25)

mmci_irq:
    - irq MCI_CMDRESPEND
    - irq MCI_DATAEND
    - send cmd12 => mmci_start_command(host->stop_abort or data->stop)
    these cmds have flag rsp_busy and no data associate
    host->cmd = cmd (host->stop_abort or data->stop) for next irq

mmci_irq:
    - irq MCI_CMDRESPEND
    - irq BUSYD0END
    - mmci_request_end

Another example is the CMD5, which has no data with it.


-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).

One second is not sufficient for all operations, like ERASE for
example. However, I understand that you want to pick some value, as a
safety. I guess that's fine.

I am thinking that if the command has the MMC_RSP_BUSY flag set, the
core should really provide a busy timeout for it. That said, maybe the
host driver should splat a WARN in case there is not busy timeout
specified.

Today, I just see a busy_timeout not defined on write request.
On erase request, the timeout is defined in function mmc_do_erase.
In core, there are several paths to done a write request, and I not
be sure to fix all. For safety, I preferred fix with the max value of
write request.


-Add MCI_DATATIMEOUT error management in mmci_cmd_irq.

Signed-off-by: Ludovic Barre <ludovic.barre@xxxxxx>
---
  drivers/mmc/host/mmci.c | 37 ++++++++++++++++++++++++++++++++-----
  drivers/mmc/host/mmci.h |  3 +++
  2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index c37e70dbe250..c50586540765 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 = 0;

         dev_dbg(mmc_dev(host->mmc), "op %02x arg %08x flags %08x\n",
             cmd->opcode, cmd->arg, cmd->flags);
@@ -1097,6 +1098,19 @@ mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
                 else
                         c |= host->variant->cmdreg_srsp;
         }
+
+       if (host->variant->busy_timeout && !host->mrq->data) {

Suppose this is a CMD12 command, having the MMC_RSP_BUSY flag set. The
command would then be sent to stop the transmission and then
host->mrq->data would also be set.

Sorry, it's a mistake introduce by v5.
I would keep the clear of datatimer when is not needed
(no data & no rsp busy, see below). But on cmd23 (set_block_count) with datactrl_first variant property the datatimer should be protected.

To simplify and fix the code, I will remove the clear of datatimer
when there is no data & no rsp busy.

- if (host->variant->busy_timeout && !host->mrq->data) {
+ if (host->variant->busy_timeout && !cmd->flags & MMC_RSP_BUSY) {
+         ....
+         writel_relaxed(clks, host->base + MMCIDATATIMER);
+ }


If I recall earlier what you stated about the new sdmmc variant, the
CMD12 is needed to exit the DPSM. Hence don't you need to re-program a
new value for the MMCIDATATIMER register for this scenario?

+               if (cmd->flags & MMC_RSP_BUSY) {
+                       if (!cmd->busy_timeout)
+                               cmd->busy_timeout = 1000;
+
+                       clks = (unsigned long long)cmd->busy_timeout;
+                       clks *= host->cclk;

Any problems with putting the above on one line?

No, it was just to not exceed 80 characters.


+                       do_div(clks, MSEC_PER_SEC);
+               }
+               writel_relaxed(clks, host->base + MMCIDATATIMER);

This is writing zero to MMCIDATATIMER in case the MMC_RSP_BUSY isn't
set, is that on purpose?

It was to clear the datatimer when the command has
no data & no rsp_busy. This allowed to look if the datatimer
was used and not correctly set with the right value (with datatimeout).

Like said above, I will remove this and set datatimer only
on rsp_busy flag.


+       }
+
         if (/*interrupt*/0)
                 c |= MCI_CPSM_INTERRUPT;

@@ -1203,6 +1217,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
  {
         void __iomem *base = host->base;
         bool sbc, busy_resp;
+       u32 err_msk;

         if (!cmd)
                 return;
@@ -1215,8 +1230,12 @@ 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)))
+       err_msk = MCI_CMDCRCFAIL | MCI_CMDTIMEOUT;

You might as well move the initial assignment of err_msk to the its
declaration above.


OK, thx

+       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 +1254,7 @@ 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 +1308,9 @@ 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;
         } else {
                 cmd->resp[0] = readl(base + MMCIRESPONSE0);
                 cmd->resp[1] = readl(base + MMCIRESPONSE1);
@@ -1948,6 +1969,8 @@ static int mmci_probe(struct amba_device *dev,
          * Enable busy detection.
          */
         if (variant->busy_detect) {
+               u32 max_busy_timeout = 0;
+
                 mmci_ops.card_busy = mmci_card_busy;
                 /*
                  * Not all variants have a flag to enable busy detection
@@ -1957,7 +1980,11 @@ static int mmci_probe(struct amba_device *dev,
                         mmci_write_datactrlreg(host,
                                                host->variant->busy_dpsm_flag);
                 mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
-               mmc->max_busy_timeout = 0;
+
+               if (variant->busy_timeout)
+                       max_busy_timeout = ~0UL / (mmc->f_max / MSEC_PER_SEC);

It looks like the max busy timeout is depending on the current picked
clock rate, right?

In such case, perhaps it's better to update mmc->max_busy_timeout as
part of the ->set_ios() callback, as it's from there the clock rate
gets updated. Or what do you think?

yes, it's possible


+
+               mmc->max_busy_timeout = max_busy_timeout;
         }

         /* Prepare a CMD12 - needed to clear the DPSM on some variants. */
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index 833236ecb31e..d8b7f6774e8f 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -287,6 +287,8 @@ struct mmci_host;
   * @signal_direction: input/out direction of bus signals can be indicated
   * @pwrreg_clkgate: MMCIPOWER register must be used to gate the clock
   * @busy_detect: true if the variant supports busy detection on DAT0.
+ * @busy_timeout: true if the variant starts data timer when the DPSM
+ *               enter in Wait_R or Busy state.
   * @busy_dpsm_flag: bitmask enabling busy detection in the DPSM
   * @busy_detect_flag: bitmask identifying the bit in the MMCISTATUS register
   *                   indicating that the card is busy
@@ -333,6 +335,7 @@ struct variant_data {
         u8                      signal_direction:1;
         u8                      pwrreg_clkgate:1;
         u8                      busy_detect:1;
+       u8                      busy_timeout:1;
         u32                     busy_dpsm_flag;
         u32                     busy_detect_flag;
         u32                     busy_detect_mask;
--
2.17.1


Kind regards
Uffe




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