On Mon, 9 Mar 2020 at 18:33, Sowjanya Komatineni <skomatineni@xxxxxxxxxx> wrote: > > > 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. Okay, good. > > 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. That seems reasonable, it becomes probably both easier and clearer by adding a new host cap. In any case, let me help out and cook a patch for this for the core part (I leave the sdhci change to you). It may be a bit tricky, especially since I have currently queued a bunch of new changes for v5.7, that enables more users of mmc_poll_for_busy() in the core. Maybe I need to temporarily drop them, so we can fix these problems first. I will check. Probably, I would also name the cap MMC_CAP_HW_NEED_RSP_BUSY, as that seems to be describing the common problem we have for sdhci omap/tegra. Finally, it seems like MMC_CAP_WAIT_WHILE_BUSY should be set for sdhci- tegra, so while at it, perhaps you can cook a patch for that as well. Kind regards Uffe
