Hello Krzysztof, On 28.03.22 14:56, Krzysztof Kozlowski wrote: > On 28/03/2022 14:45, Adam Ford wrote: >> On Mon, Mar 28, 2022 at 6:49 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote: >>> >>> On 28/03/2022 13:09, Ahmad Fatoum wrote: >>>> Hello Adam, >>>> >>>> On 28.03.22 12:47, Adam Ford wrote: >>>>> On Mon, Mar 28, 2022 at 2:20 AM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: >>>>>> >>>>>> Hello Adam, >>>>>> >>>>>> On 27.03.22 14:38, Adam Ford wrote: >>>>>>> The SDHC controller in the imx8mp has the same controller >>>>>>> as the imx8mm which supports HS400-ES. Change the compatible >>>>>>> fallback to imx8mm to enable it. >>>>>> >>>>>> I believe that's a shortcoming of the Linux driver, which should explicitly list >>>>>> fsl,imx8mp-usdhc in its compatibles and enable HS400-ES for it. >>>>>> >>>>>> I find dropping compatibles problematic, because like Linux matching >>>>>> fsl,imx8mm-usdhc, but not fsl,imx8mp-usdhc, other software may match >>>>>> fsl,imx7d-usdhc, but not fsl,imx8[mp]-usdhc. >>>>>> >>>>>> I'd prefer that either the kernel driver gains extra compatibles or that >>>>>> the DTS lists extra compatibles and we refrain from dropping existing >>>>>> (correct) ones. >>>>>> >>>>> >>>>> I would argue that imx7d is not correct since the IP blocks between >>>>> imx7d and imx8mm have different flags/quirks. One of which includes >>>>> HS400-ES, but there are other differences as well. >>>> >>>> The DTS currently says that an fsl,imx7d-usdhc is a subset of an >>>> fsl,imx8mm-usdhc. So a driver could treat both HW the exact same >>>> by focusing on the i.MX7D parts. Linux apparently did exactly >>>> that so far. Is this not accurate? >>>> >>>> >>>>>> What do you think? >>>>> >>>>> From my understanding of the fallback compatibility strings is to >>>>> avoid having to add more and more compatible strings to the drivers >>>>> when they do not serve a functional purpose. Based On a conversation >>>>> with Krzysztof [1], he suggested we update the YAML file based on the >>>>> fallback, but he wanted NXP to give their feedback as to what the >>>>> right fallback strings should be. Haibo from NXP sent me a hierarchy >>>>> [1] which is what I used to update the YAML file. Based on the YAML >>>>> file, the fallback in each DTSI file was updated to ensure the use of >>>>> the proper IP block. >>>> >>>> Myself I am in favor of moving to three compatibles instead of dropping one. >>>> For some theoretical fsl,imx8mf-usdhc that's supposed to be exactly the same >>>> as a fsl,imx8mm-usdhc, I don't mind omitting the fsl,imx7d-usdhc compatible, >>>> but for existing device trees, this may introduce needless potential breakage >>>> for other software that also uses Linux device trees. >>>> >>> >>> Affecting existing users is indeed a concern with this approach, because >>> in-kernel DTS might be used in other projects as well. >>> >>> I still cannot find here the answer whether fsl,imx8mm-usdhc is actually >>> compatible with fsl,imx7d-usdhc. It's not about driver, but about >>> hardware and programming model. imx8mm can support additional features >>> and still be compatible with imx7d. However if any flags of imx7d are >>> actually not valid for imx8mm, then it's different case. >> >> The imx7d flags are: >> ESDHC_FLAG_USDHC >> ESDHC_FLAG_STD_TUNING >> ESDHC_FLAG_HAVE_CAP1 >> ESDHC_FLAG_HS200 >> ESDHC_FLAG_HS400 >> ESDHC_FLAG_STATE_LOST_IN_LPMODE >> ESDHC_FLAG_BROKEN_AUTO_CMD23, >> >> The imx8mm flags are: >> ESDHC_FLAG_USDHC >> ESDHC_FLAG_STD_TUNING >> ESDHC_FLAG_HAVE_CAP1 >> ESDHC_FLAG_HS200 >> ESDHC_FLAG_HS400 >> ESDHC_FLAG_HS400_ES >> ESDHC_FLAG_STATE_LOST_IN_LPMODE >> >> It does not have the ESDHC_FLAG_BROKEN_AUTO_CMD23 that is present in the imx7d. > > AFAIU, it looks imx8mm is compatible with imx7d, because the broken > acmd23 only limits the features. If imx8mm binds according to imx7d, it > will not support acmd23 and HS400-ES. > > Having three compatibles is therefore also OK. My thoughts, exactly. > You could also add two cases: > 1. three compatibles, deprecated: True, > 2. two compatibles, without imx7d. > > Existing DTS stays with three compatibles for two years and later gets > converted to two compatibles. New DTS should use two compatibles. > > It's quite a lot of churn, but would make in the long term bindings > correct and also not break other users/projects. I don't see why we need to deprecate the old binding. New SoCs can be imx8mm-usdhc compatible from the beginning and need not care about the old binding. Existing SoCs can just remain imx7d-usdhc compatible as they are now. I don't see what the deprecation accomplishes. >> Maybe Haibo can comment on whether or not that would be an issue for the 8m[mnp] >> >> I will defer to Krzysztof and Haibo as to the proper method that we >> should add HS400-ES. I don't have an issue adding the imx8mn or >> imx8mp compatible flags to the esdhc driver if that's the decision. > > I don't get what's the problem with HS400-ES. In any case (your patch > here, other ideas) your DTS will bind to imx8mm-usdhc which has HS400-ES. Cheers, Ahmad > Best regards, > Krzysztof -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
