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. 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.
