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SubjectRe: [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@linaro.org> wrote:
>>
>> On Thu, 5 Sep 2019 at 14:21, Ludovic Barre <ludovic.Barre@st.com> wrote:
>>>
>>> From: Ludovic Barre <ludovic.barre@st.com>
>>>
>>> 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@st.com>
>>> ---
>>> 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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