Messages in this thread | | | Subject | Re: [PATCH v1] sdhci: tegra: Remove warnings about missing device-tree properties | From | Sowjanya Komatineni <> | Date | Tue, 19 May 2020 13:44:18 -0700 |
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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@gmail.com> >>>>>>> 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.
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