On 28/03/2022 15:12, Ahmad Fatoum wrote: > Hello Adam, > > On 28.03.22 15:06, Adam Ford wrote: >> On Mon, Mar 28, 2022 at 7:56 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> 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. >>> >>> 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. >>> >>>> >>>> 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. >> >> I was under the impression Ahmad didn't want me to add the imx8mm >> compatible to the DTS, but instead, add the imx8mp compatible into the >> driver so it binds directly to an imx8mp. It's not really related the bindings, so don't ask me. Best regards, Krzysztof
