Uffe, On 06/03/20 4:44 pm, Ulf Hansson wrote: > [...] > >>>>>>>>>>> >>>>>>>>>>> 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. > I was able to reproduce the issue on sdhci-omap with your patch applied. In our case, the dat0 line never comes back up when trying to send a CMD6 with R1. It needs an R1b to work properly. I also set mmc->max_busy_timeout to 0 and that made it work as well. I wanna try it out with other R1b commands like erase to see if it works properly if the delay is actually very long. Thanks, Faiz
