Messages in this thread | | | Subject | Re: [PATCH 1/4] mmc: mmci: avoid fake busy polling | From | Ludovic BARRE <> | Date | Thu, 25 Apr 2019 16:09:35 +0200 |
| |
On 4/25/19 12:08 PM, Ulf Hansson wrote: > On Thu, 25 Apr 2019 at 11:22, Ludovic BARRE <ludovic.barre@st.com> wrote: >> >> hi Ulf >> >> On 4/23/19 3:39 PM, Ulf Hansson wrote: >>> On Tue, 5 Mar 2019 at 17:10, Ludovic Barre <ludovic.Barre@st.com> wrote: >>>> >>>> From: Ludovic Barre <ludovic.barre@st.com> >>>> >>>> The busy status bit could occurred even if no busy response is >>>> expected (example cmd11). On sdmmc variant, the busy_detect_flag >>>> reflects inverted value of d0 state, it's sampled at the end of a >>>> CMD response and a second time 2 clk cycles after the CMD response. >>>> To avoid a fake busy, the busy status could be checked and polled >>>> only if the command has RSP_BUSY flag. >>> >>> I would appreciate a better explanation of what this patch really changes. >>> >>> The above is giving some background to the behavior of sdmmc variant, >>> but at this point that variant doesn't even have the >>> ->variant->busy_detect flag set. >>> >> >> Yes, I will try to explain more and focus on common behavior. >> >>>> >>>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com> >>>> --- >>>> drivers/mmc/host/mmci.c | 19 +++++++++++++------ >>>> 1 file changed, 13 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c >>>> index 387ff14..4901b73 100644 >>>> --- a/drivers/mmc/host/mmci.c >>>> +++ b/drivers/mmc/host/mmci.c >>>> @@ -1220,12 +1220,13 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd, >>>> unsigned int status) >>>> { >>>> void __iomem *base = host->base; >>>> - bool sbc; >>>> + bool sbc, busy_resp; >>>> >>>> if (!cmd) >>>> return; >>>> >>>> sbc = (cmd == host->mrq->sbc); >>>> + busy_resp = !!(cmd->flags & MMC_RSP_BUSY); >>>> >>>> /* >>>> * We need to be one of these interrupts to be considered worth >>>> @@ -1239,8 +1240,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd, >>>> /* >>>> * ST Micro variant: handle busy detection. >>>> */ >>>> - if (host->variant->busy_detect) { >>>> - bool busy_resp = !!(cmd->flags & MMC_RSP_BUSY); >>>> + if (busy_resp && host->variant->busy_detect) { >>>> >>>> /* We are busy with a command, return */ >>>> if (host->busy_status && >>>> @@ -1253,7 +1253,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd, >>>> * that the special busy status bit is still set before >>>> * proceeding. >>>> */ >>>> - if (!host->busy_status && busy_resp && >>>> + if (!host->busy_status && >>>> !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) && >>>> (readl(base + MMCISTATUS) & host->variant->busy_detect_flag)) { >>> >>> All the changes above makes perfect sense to me, but looks more like a >>> cleanup of the code, rather than actually changing the behavior. >> >> yes, few changing (this just avoid to enter in >> "if (host->variant->busy_detect)") at each time. >> I could move this part in cleanup patch (before this patch) > > Sounds good to me! > >> >>> >>>> >>>> @@ -1508,6 +1508,7 @@ static irqreturn_t mmci_irq(int irq, void *dev_id) >>>> { >>>> struct mmci_host *host = dev_id; >>>> u32 status; >>>> + bool busy_resp; >>>> int ret = 0; >>>> >>>> spin_lock(&host->lock); >>>> @@ -1550,9 +1551,15 @@ static irqreturn_t mmci_irq(int irq, void *dev_id) >>>> } >>>> >>>> /* >>>> - * Don't poll for busy completion in irq context. >>>> + * Don't poll for: >>>> + * -busy completion in irq context. >>>> + * -no busy response expected. >>>> */ >>>> - if (host->variant->busy_detect && host->busy_status) >>>> + busy_resp = host->cmd ? >>>> + !!(host->cmd->flags & MMC_RSP_BUSY) : false; >>> >>> This doesn't make sense to me, but I may be missing something. >>> >>> host->busy_status is being updated by mmci_cmd_irq() and only when >>> MMC_RSP_BUSY is set for the command in flight. In other words, >>> checking for MMC_RSP_BUSY here as well is redundant. No? >> >> In mmci_irq the "do while" loops until the status is totally cleared. >> >> Today (for variant with busy_detect option), the status busy_detect_flag >> is excluded only while busy_status period (command with MMC_RSP_BUSY and >> while busy line is low => "busy_status=1") >> >> On SDMMC variant I noticed that busy_detect_flag status could be enabled >> even if the command is not MMC_RSP_BUSY, for example sdmmc variant stay >> in loop while cmd11 voltage switch. > > Right, I see. > >> >> So I wish extend host->variant->busy_detect_flag exclusion for all >> commands which is not a MMC_RSP_BUSY. I suppose that other variants >> could have the same behavior, and else there is no impact, normally. > > I am guessing this is because the variant->busy_dpsm_flag has been set > in the datactrl register, which is needed for mmci_card_busy(). > > That said, I am kind of wondering if we ever should need repeat the > while loop if 'status' contains the bit for > host->variant->busy_detect_flag. I mean we have already called > mmci_cmd_irq() to handle it. > > So, couldn't we just always do: > > if (host->variant->busy_detect_flag) > status &= ~host->variant->busy_detect_flag; > > No?
yes that make sense, I launched tests on sdmmc and it's ok. I think, that we could take on this solution.
If it's ok for you, I resend a series with all modifications.
Regards Ludo
> >> >>> >>>> + >>>> + if (host->variant->busy_detect && >>>> + (!busy_resp || host->busy_status)) >>>> status &= ~host->variant->busy_detect_flag; >>>> >>>> ret = 1; >>>> -- >>>> 2.7.4 >>>> >>> >>> Kind regards >>> Uffe >>> > > Kind regards > Uffe >
| |