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

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hi Ulf

Le 10/4/19 à 8:20 AM, Ulf Hansson a écrit :
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




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