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Date: Mon, 7 Oct 2019 08:48:35 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Ludovic BARRE <ludovic.barre@...com>
Cc: Rob Herring <robh+dt@...nel.org>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexandre Torgue <alexandre.torgue@...com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
DTML <devicetree@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V6 1/3] mmc: mmci: add hardware busy timeout feature
On Fri, 4 Oct 2019 at 14:59, Ludovic BARRE <ludovic.barre@...com> wrote:
>
> 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@...aro.org> wrote:
> >>
> >> On Thu, 5 Sep 2019 at 14:21, Ludovic Barre <ludovic.Barre@...com> wrote:
> >>>
> >>> From: Ludovic Barre <ludovic.barre@...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@...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.
Right, thanks for clarifying!
>
> 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?
For the legacy variant, the MCI_DATATIMEOUT isn't an issue as it can't
be raised while waiting for busyend. So, I think this is fine as is.
Kind regards
Uffe
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