Messages in this thread | | | Subject | Re: LKFT: arm x15: mmc1: cache flush error -110 | From | Sowjanya Komatineni <> | Date | Mon, 9 Mar 2020 10:35:31 -0700 |
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On 3/6/20 3:14 AM, Ulf Hansson wrote: > External email: Use caution opening links or attachments > > > [...] > >>>>>>>>>>> Actually we always use R1B with CMD6 as per spec. >>>>>>>>>> I fully agree that R1B is preferable, but it's not against the >>>>>>>>>> spec to >>>>>>>>>> send CMD13 to poll for busy. >>>>>>>>>> >>>>>>>>>> Moreover, we need to cope with the scenario when the host has >>>>>>>>>> specified a maximum timeout that isn't sufficiently long enough for >>>>>>>>>> the requested operation. Do you have another proposal for how to >>>>>>>>>> manage this, but disabling MMC_RSP_BUSY? >>>>>>>>>> >>>>>>>>>> Let's assume you driver would get a R1B for the CMD6 (we force it), >>>>>>>>>> then what timeout would the driver be using if we would set >>>>>>>>>> cmd.busy_timeout to 30ms? >>>>>>>>>> >>>> Sorry didn't understood clearly. Are you asking with 30s timeout, whats >>>> the data timeout counter used? >>> Yes. It seems like it will pick the maximum, which is 11s? >> yes > Okay, thanks! > >>>> Because of above mentioned issue on our host where CMD interrupt happens >>>> after busy state, poll for busy returns right away as not busy. >>> I see. >>> >>>> So issuing CMD13 after CMD6-R1 followed by busy poll should be working. >>>> But weird that with small delay of 1ms or debug print before CMD13 it >>>> doesn't timeout and works all the time. >>> I have digested the information you provided in these emails. Let me >>> summarize it, to see if I have understood correctly. >>> >>> 1. >>> Your controller can't distinguish between R1 and R1B because of a >>> limitation in the HW. So, in both cases you need to wait for the card >>> to stop signal busy, before the controller can give an IRQ to notify >>> that the R1 response has been received. Correct? >>> >>> In this context, I am wondering if sdhci_send_command(), really >>> conforms to these requirements. For example, depending on if the CMD6 >>> has MMC_RSP_BUSY or not, it may pick either SDHCI_CMD_RESP_SHORT or >>> SDHCI_CMD_RESP_SHORT_BUSY. >>> >>> Does this work as expected for your case? >> Design team re-verified internally and bug where HW waits for busy state >> before IRQ is only for R1B and R1 is spec compliant. >> >> So, with R1, CMD complete is generated after response received. > Okay. > > So, the issue we see for CMD6 with R1, is a software problem that we > should be able to fix. > >> With R1B, CMD complete and xfer complete both are generated after >> response received + device busy (max timeout of 11s) >> DATA timeout interrupt will be asserted incase if HW busy detection fails. >> >> With R1B we may see DATA Timeout if operation takes more than max busy >> timeout of 11s. > Okay, I see. > >>> 2. >>> Assuming my interpretation of the above is somewhat correct. Then you >>> always need to set a busy timeout for R1/R1B responses in the >>> controller. The maximum timeout seems to be 11s long. Obviously, this >>> isn't enough for all cases, such as cache flushing and erase, for >>> example. So, what can we do to support a longer timeouts than 11s? >>> Would it be possible to disable the HW timeout, if the requested >>> timeout is longer than 11s and use a SW timeout instead? >>> >>> Kind regards >>> Uffe >> For erase long operations we have register bit to enable for infinite >> busy wait mode where host controller would be monitoring until card is busy. > Alright, that sounds great! > >> But so far for emmc devices we used on our platforms, we haven't seen >> cache flush taking more than 11s. > I understand that 11s is probably fine to use, for most cases. > > However, it's not spec compliant, as for some operations there are > simply no timeout specified. BKOPS, cache flush, sanitize are cases > like this - and then 11s is definitely not sufficient. > >> Will get back on possibility of disabling HW timeout and using SW timeout.. > Thanks! > > I would like to get the regression fixed asap, but I also would like > to avoid reverting patches, unless really necessary. May I propose the > following two options. > > 1. Find out why polling with ->card_busy() or CMD13, for a CMD6 with > an R1 response doesn't work - and then fix that behaviour. > > 2. Set the mmc->max_busy_timeout to zero for sdhci-tegra, which makes > the core to always use R1B for CMD6 (and erase). This also means that > when the cmd->busy_timeout becomes longer than 11s, sdhci-tegra must > disable the HW busy timeout and just wait "forever". > > If you decide for 2, you can add the software timeout support on top, > but make that can be considered as a next step of an improvement, > rather than needed as fix. Note that, I believe there are some support > for software timeout already in the sdhci core, maybe you need to > tweak it a bit for your case, I don't know. > > Kind regards > Uffe
Hi Uffe
Will go with 2nd option and will send patches out when ready.
BTW, Tegra host also supports SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK for data timeout based on host clock when using finite mode (HW busy detection based on DATA TIMEOUT count value when cmd operation timeout is < 11s for tegra host).
So, looks like we cant set host max_busy_timeout to 0 for Tegra host to force R1B during SWITCH and SLEEP_AWAKE.
So, was thinking to introduce host capability MMC_CAP2_LONG_WAIT_HW_BUSY which can be used for hosts supporting long or infinite HW busy wait detection and will update mmc and mmc_ops drivers to not allow convert R1B to R1B for hosts with this capability during SLEEP_AWAKE and SWITCH.
Thanks
Sowjanya
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