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 11:41:40 -0700 |
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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.
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