22.05.2020 15:13, Thierry Reding пишет: > On Wed, May 20, 2020 at 09:09:33AM -0700, Sowjanya Komatineni wrote: >> >> On 5/20/20 4:26 AM, Ulf Hansson wrote: >>> On Wed, 20 May 2020 at 04:00, Dmitry Osipenko <digetx@xxxxxxxxx> wrote: >>>> 19.05.2020 23:44, Sowjanya Komatineni пишет: >>>>> On 5/19/20 12:07 PM, Sowjanya Komatineni wrote: >>>>>> On 5/19/20 11:41 AM, Sowjanya Komatineni wrote: >>>>>>> On 5/19/20 11:34 AM, Sowjanya Komatineni wrote: >>>>>>>> On 5/19/20 9:33 AM, Dmitry Osipenko wrote: >>>>>>>>> 19.05.2020 19:24, Thierry Reding пишет: >>>>>>>>>> On Tue, May 19, 2020 at 05:05:27PM +0300, Dmitry Osipenko wrote: >>>>>>>>>>> 19.05.2020 10:28, Ulf Hansson пишет: >>>>>>>>>>>> On Sat, 16 May 2020 at 17:44, Dmitry Osipenko <digetx@xxxxxxxxx> >>>>>>>>>>>> wrote: >>>>>>>>>>>>> Several people asked me about the MMC warnings in the KMSG log and >>>>>>>>>>>>> I had to tell to ignore them because these warning are >>>>>>>>>>>>> irrelevant to >>>>>>>>>>>>> pre-Tegra210 SoCs. >>>>>>>>>>>> Why are the warnings irrelevant? >>>>>>>>>>> That's what the DT binding doc says [1]. >>>>>>>>>>> >>>>>>>>>>> [1] >>>>>>>>>>> https://www.kernel.org/doc/Documentation/devicetree/bindings/mmc/nvidia%2Ctegra20-sdhci.txt >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Although, looking at the driver's code and TRM docs, it seems >>>>>>>>>>> that all >>>>>>>>>>> those properties are really irrelevant only to the older Terga20 >>>>>>>>>>> SoC. So >>>>>>>>>>> the binding doc is a bit misleading. >>>>>>>>>>> >>>>>>>>>>> Nevertheless, the binding explicitly says that the properties are >>>>>>>>>>> optional, which is correct. >>>>>>>>>> Optional only means that drivers must not fail if these properties >>>>>>>>>> aren't found, it doesn't mean that the driver can't warn that they >>>>>>>>>> are missing. >>>>>>>>>> >>>>>>>>>> Quite possibly the only reason why they were made optional is because >>>>>>>>>> they weren't part of the bindings since the beginning. Anything added >>>>>>>>>> to a binding after the first public release has to be optional by >>>>>>>>>> definition, otherwise DT ABI wouldn't be stable. >>>>>>>>>> >>>>>>>>>> I think these warnings were added on purpose, though I also see that >>>>>>>>>> there are only values for these in device tree for Tegra186 and >>>>>>>>>> Tegra194 >>>>>>>>>> but not Tegra210 where these should also be necessary. >>>>>>>> dt binding doc we have is common for MMC, SD and SDIO of all Tegras. >>>>>>>> Its not mandatory to have both 3v3 and 1v8 in device tree as based >>>>>>>> on signal mode. >>>>>>>> >>>>>>>> As these driver strengths are SoC specific, they are part of Tegra >>>>>>>> SoC specific device tree where same values will be applicable to all >>>>>>>> Tegra SoC specific platforms. >>>>>>>> >>>>>>>> Based on interface usage on platform, we use one or both of them >>>>>>>> like sdcard supports dual voltage and we use both 3V3 and 1V8 but if >>>>>>>> same interface is used for WIFI SD we use 1V8 only. >>>>>>>> >>>>>>>> So made these dt properties as optional. >>>>>>>> >>>>>>>> Other reason they are optional is, Tegra210 and prior has drive >>>>>>>> strength settings part of apb_misc and Tegra186 and later has driver >>>>>>>> strengths part of SDMMC controller. So, >>>>>>>> >>>>>>>> - Pinctrls "sdmmc-3v3-drv" and "sdmmc-1v8-drv" for driver strengths >>>>>>>> are applicable for Tegra210 and prior. >>>>>>>> - dt properties pad-autocal-pull-up/down-offset-1v8/3v3-timeout are >>>>>>>> for T186 onwards for driver strengths >>>>>>>> >>>>>>>> Looks like dt binding doc need fix to clearly document these based >>>>>>>> on SoC or agree with Yaml we can conditionally specify pinctrl or dt >>>>>>>> properties based on SoC dependent. >>>>>>>> >>>>>>>> >>>>>>>>>> Adding Sowjanya who wrote this code. Perhaps she can clarify why the >>>>>>>>>> warnings were added. If these values /should/ be there on a subset of >>>>>>>>>> Tegra, then I think we should keep them, or add them again, but >>>>>>>>>> perhaps >>>>>>>>>> add a better way of identifying when they are necessary and when >>>>>>>>>> it is >>>>>>>>>> safe to work without them. >>>>>>>>>> >>>>>>>>>> That said, looking at those checks I wonder if they are perhaps just >>>>>>>>>> wrong. Or at the very least they seem redundant. It looks to me like >>>>>>>>>> they can just be: >>>>>>>>>> >>>>>>>>>> if (tegra_host->pinctrl_state_XYZ == NULL) { >>>>>>>>>> ... >>>>>>>>>> } >>>>>>>>>> >>>>>>>>>> That !IS_ERR(...) doesn't seem to do anything. But in that case, it's >>>>>>>>>> also obvious why we're warning about them on platforms where these >>>>>>>>>> properties don't exist in DT. >>>>>>>> As drive strengths are through dt properties for T186 and later and >>>>>>>> thru pinctrl for T210 and prior, driver first checks for dt autocal >>>>>>>> timeout pull-up/down properties and if they are not found, it then >>>>>>>> checks for presence of pinctrl_state_xyx_drv only when valid >>>>>>>> pinctrl_state_xyz is present. >>>>>>>> >>>>>>>> Driver expects either pinctrl or dt properties and shows warning >>>>>>>> when neither of them are present as its mandatory to use fixed >>>>>>>> driver strengths when auto calibration fails. >>>>>>>> >>>>>>>> err = device_property_read_u32(host->mmc->parent, >>>>>>>> "nvidia,pad-autocal-pull-down-offset-3v3-timeout", >>>>>>>> &autocal->pull_down_3v3_timeout); >>>>>>>> if (err) { >>>>>>>> if (!IS_ERR(tegra_host->pinctrl_state_3v3) && >>>>>>>> (tegra_host->pinctrl_state_3v3_drv == NULL)) >>>>>>>> pr_warn("%s: Missing autocal timeout 3v3-pad drvs\n", >>>>>>>> mmc_hostname(host->mmc)); >>>>>>>> autocal->pull_down_3v3_timeout = 0; >>>>>>>> } >>>>>>>> >>>>>>>>>> So I think we either need to add those values where appropriate so >>>>>>>>>> that >>>>>>>>>> the warning doesn't show, or we need to narrow down where they are >>>>>>>>>> really needed and add a corresponding condition. >>>>>>>>>> >>>>>>>>>> But again, perhaps Sowjanya can help clarify if these really are only >>>>>>>>>> needed on Tegra210 and later or if these also apply to older chips. >>>>>>>>> Either way will be cleaner to convert the DT binding to YAML rather >>>>>>>>> than >>>>>>>>> clutter the driver, IMO. >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> Auto calibration is present from Tegra30 onward and looking into >>>>>>> change where autocalibration was added to sdhci driver somehow it was >>>>>>> enabled only for T30/T210/T186/T194. >>>>>>> >>>>>>> tegra_sdhci_parse_pad_autocal_dt() was added when auto-calibration >>>>>>> was added to driver and I see this dt parse is being done >>>>>>> irrespective of NVQUIRK_HAS_PADCALIB quirk so even on platforms >>>>>>> without auto cal enabled in driver, these messages shows up. >>>>>>> >>>>>>> This should be fixed in driver to allow >>>>>>> tegra_sdhci_parse_pad_autocal_dt() only when NVQUIRK_HAS_PADCALIB is >>>>>>> set to avoid dt parsing to happen on platforms that don't have auto >>>>>>> cal enabled. >>>>>> Warning on missing drive strengths when auto cal is enabled should be >>>>>> present as we should switch to fixed recommended drive strengths when >>>>>> auto cal fails. >>>>>> >>>>>> So probably proper fix should be >>>>>> >>>>>> - allow tegra_sdhci_parse_pad_autocal_dt() only when >>>>>> NVQUIRK_HAS_PADCALIB is set >>>>>> >>>>>> - current driver sets NVQUIRK_HAS_PADCALIB for T30 as well so need to >>>>>> add pinctrls "sdmmc-3v3-drv" and "sdmmc-1v8-drv" to Tegra30 device tree. >>>>> [Correction] T30 has same drive strengths to use irrespective of signal >>>>> voltage and it doesn't have pad control. So for T3- we can update device >>>>> tree to specify "default" pinctrl with drvup/dn settings. >>>>>> - Keep warning message of missing auto cal timeouts as its mandatory >>>>>> to use fixed recommended driver strengths when auto cal fails. >>>>>> >>>>> Regarding warnings, I guess simpler and easy fix is to remove warning >>>>> message on missing 3v3/1v8 drive strengths as pinctrl/dt properties were >>>>> already added for T210/186/194 where we need and old device tree don't >>>>> have them but the case where auto cal can fail is very rare. >>>>> >>>>> Otherwise should update driver to allow >>>>> tegra_sdhci_parse_pad_autocal_dt() only when NVQUIRK_HAS_PADCALIB is set >>>>> and also within tegra_sdhci_parse_pad_autocal_dt() show warning of >>>>> missing 3v3/1v8 settings only when NVQUIRK_NEEDS_PAD_CONTROL is set. >>>>> >>>>> Thierry, please suggest if you prefer to removing warnings or fix driver >>>>> to show warning based on PADCALIB and PAD_CONTROL quirks. >>>> The SDIO PINCTRL drive-strengths are usually a part of the board's >>>> default PINCTRL state, which is either preset by bootloader or by >>>> PINCTRL driver early at a boot time. >>>> >>>> The SDIO drive-strengths values should be board-specific and not >>>> SoC-specific because they should depend on the electrical properties of >>>> the board, IIUC. >> >> Drive strengths we program here when auto calibration fails are recommended >> values based on pre-SI circuit analysis and characterized across PVT. >> >> So, these fail safe values are same for all boards of specific SoC as all >> platform designs follow the design guidelines. >> >>>> If the SDIO PINCTRL states are mandatory for the SDHCI nodes in the >>>> device-trees, then the DT binding is wrong since it says that all >>>> properties are optional. But I think that the current binding is okay, >>>> since today SDHCI PINCTRL drive-strengths are specified implicitly in >>>> the device-trees, and thus, there is no real need to emit the noisy >>>> warnings in this case. >>> For now I will keep $subject patch applied, but please tell me if I >>> should drop it so we can start over. >>> >>> In any case, I would appreciate it if someone could have a stab at >>> converting sdhci and tegra DT bindings to yaml. >>> >>> Kind regards >>> Uffe >> >> HI Uffe, >> >> Please drop $subject patch. Will send patch that allows parsing for these >> properties only for SoC where auto cal is enabled as that's where driver >> needs these properties. >> >> So with this fix, warning will not show up on systems where autocal is not >> enabled. > > Yes, I think that's a better option. Have we ensured that on all systems > where autocal is enabled these values are part of the device tree? Just > making sure that we're not going to have some generation still spit out > these warnings because we forgot to update the device tree. > > For example I see that we set NVQUIRK_HAS_PADCALIB but I don't see these > properties being set in arch/arm/boot/dts/tegra30.dtsi. Can you add a > patch that also adds the properties for Tegra30? I don't see the warnings on T30 using Sowjanya's patch which checks for NVQUIRK_NEEDS_PAD_CONTROL and not NVQUIRK_HAS_PADCALIB.
