Messages in this thread | | | Subject | Re: [Linux-stm32] [PATCH V3 1/3] mmc: mmci: fix read status for busy detect | From | Ludovic BARRE <> | Date | Mon, 5 Aug 2019 09:33:21 +0200 |
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hi Ulf
On 7/26/19 11:41 AM, Ludovic BARRE wrote: > hi Ulf > > Thanks to your "Clarify comments ..." commit, like is closes > I resumed upstream of this series. > > On 7/15/19 6:31 PM, Ulf Hansson wrote: >> On Mon, 3 Jun 2019 at 17:55, Ludovic Barre <ludovic.Barre@st.com> wrote: >>> >>> From: Ludovic Barre <ludovic.barre@st.com> >>> >>> "busy_detect_flag" is used to read & clear busy value of mmci status. >>> "busy_detect_mask" is used to manage busy irq of mmci mask. >>> So to read mmci status the busy_detect_flag must be take account. >>> if the variant does not support busy detect feature the flag is null >>> and there is no impact. >> >> By reading the changelog, it doesn't tell me the purpose of this >> change. When going forward, please work harder on your changelogs. >> >> Make sure to answer the questions, *why* is this change needed, >> *what/how* does the change do. > > Ok, I will explain the differences with the legacy and the needs of > sdmmc variant about busy detection. > >> >>> >>> Not need to re-read the status register in mmci_cmd_irq, the >>> status parameter can be used. >>> >>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com> >>> --- >>> drivers/mmc/host/mmci.c | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c >>> index 356833a..5b5cc45 100644 >>> --- a/drivers/mmc/host/mmci.c >>> +++ b/drivers/mmc/host/mmci.c >>> @@ -1240,7 +1240,7 @@ mmci_cmd_irq(struct mmci_host *host, struct >>> mmc_command *cmd, >>> */ >>> if (!host->busy_status && >>> !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) && >>> - (readl(base + MMCISTATUS) & >>> host->variant->busy_detect_flag)) { >>> + (status & host->variant->busy_detect_flag)) { >> >> I suggested you to do this change through some of my earlier comments, >> however I think it should be made as a stand alone change. >> >> Anyway, when looking at the details in your series, I decided to try >> to help out a bit, so I have prepared a couple of related patches for >> cleaning up and clarifying the busy detection code/comments in mmci. I >> have incorporated the above change, so let me post them asap. >> >>> >>> /* Clear the busy start IRQ */ >>> writel(host->variant->busy_detect_mask, >>> @@ -1517,7 +1517,8 @@ static irqreturn_t mmci_irq(int irq, void *dev_id) >>> * to make sure that both start and end interrupts >>> are always >>> * cleared one after the other. >>> */ >>> - status &= readl(host->base + MMCIMASK0); >>> + status &= readl(host->base + MMCIMASK0) | >>> + host->variant->busy_detect_flag; >> >> As I told earlier in the review, this looks wrong to me. >> >> It means that you will add the bit for the ->busy_detect_flag to the >> status field we have just read from the MMCISTATUS register. That >> means the busy status may be set when it shouldn't. >> >>> if (host->variant->busy_detect) >>> writel(status & >>> ~host->variant->busy_detect_mask, >>> host->base + MMCICLEAR); >>> -- >>> 2.7.4 >>> >> >> By looking at the other changes in the series, I assume @subject patch >> is intended to prepare for the other changes on top. But it's not >> really clear. >> >> Anyway, in that regards, the below is my observations of what seems to >> be important part, when supporting busy detection for the stm32 sdmmc >> variant (except the timeout things in patch2, which I intend to >> comment separately on). >> >> I figured, these are the involved register bits/masks: >> >> MMCISTATUS: >> MCI_STM32_BUSYD0 BIT(20) >> MCI_STM32_BUSYD0END BIT(21) >> >> MMCIMASK0: >> MCI_STM32_BUSYD0ENDMASK BIT(21) > > it's exact: > MCI_STM32_BUSYD0 BIT(20): This is a hardware status flag only (inverted > value of d0 line), it does not generate an interrupt, and so no mask > bit. > > MCI_STM32_BUSYD0ENDMASK BIT(21): This indicates only end of busy > following a CMD response. On busy to Not busy changes, an interrupt > is generated (if unmask) and BUSYD0END status flag is set. > status flag is cleared by writing corresponding interrupt clear bit in > MMCICLEAR. > >> >> For the legacy ST variant, there is only one register bit in >> MMCISTATUS that is used for indicating busy (MCI_ST_CARDBUSY BIT(24)). >> There is no dedicated busy-end bit for the busy-end IRQ, which I >> believe is the reason to why the current code also is bit messy. > > yes > >> >> It seems like the stm32 sdmmc variant have a separate status bit for >> the busy-end IRQ, correct? > > yes > >> >> If I understand correctly by looking at patch3, you don't use the >> dedicated busy-end status bit (MCI_STM32_BUSYD0END), right? Then why >> not? > > like your are clarify in previous series, the busy detection is done > in 3 steps. > > if I use: > .busy_detect_flag = MCI_STM32_BUSYD0ENDMASK, > .busy_detect_mask = MCI_STM32_BUSYD0ENDMASK, > > the sdmmc request will be not correctly completed, because the third > step can't be happen. > > chronologies: > step1: when busyd0end change to 1 > => busyd0end interrupt is unmasked > => busy_status = cmd_sent | respend > => return to mmci_irq > step2: busyd0end is yet to 1 > => clear the busyd0end interrupt > => the hardware clear busyd0end status flag on interrupt clear > => return to mmci_irq > > like MCI_STM32_BUSYD0END interrupt is generated only on change > busy to not busy, when the interrupt is cleared (status is 0) > the step 3 can't happen (no irq pending to re-enter in mmci_cmd_irq). > sdmmc can't complete the request. > > If I use: > .busy_detect_flag = MCI_STM32_BUSYD0, > .busy_detect_mask = MCI_STM32_BUSYD0ENDMASK, > > Like there is no MCI_STM32_BUSYD0 irq mask, the status read in mmci_irq > "status &= readl(host->base + MMCIMASK0)" can't take account the > busy_detect_flag (for sdmmc). So the step 2 can't be passed. > However we could share re-read between step 1 and step 2. > > proposal: > > + > + u32 busy_val = readl(base + MMCISTATUS) & > + host->variant->busy_detect_flag; > + > if (!host->busy_status && > - !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) && > - (readl(base + MMCISTATUS) & > host->variant->busy_detect_flag)) { > + !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) && busy_val) { > > writel(readl(base + MMCIMASK0) | > host->variant->busy_detect_mask, > @@ -1262,8 +1265,7 @@ mmci_cmd_irq(struct mmci_host *host, struct > mmc_command *cmd, > * both the start and the end interrupts needs to be cleared, > * one after the other. So, clear the busy start IRQ here. > */ > - if (host->busy_status && > - (status & host->variant->busy_detect_flag)) { > + if (host->busy_status && busy_val) { > > > what do you think about it ? >
I give up this proposal for a new version based on mmci_host_ops callback to done the busy completion.
>> >> Thoughts? >> >> Kind regards >> Uffe >> > > Regards > Ludo > _______________________________________________ > Linux-stm32 mailing list > Linux-stm32@st-md-mailman.stormreply.com > https://st-md-mailman.stormreply.com/mailman/listinfo/linux-stm32
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