Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 09 Mar 2023 09:39:54 +0100 | From | Rafał Miłecki <> | Subject | Re: [PATCH V2] nvmem: add explicit config option to read OF fixed cells |
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On 2023-03-09 09:34, Miquel Raynal wrote: > Hi Rafał, > > zajec5@gmail.com wrote on Thu, 9 Mar 2023 07:56:05 +0100: > >> On 8.03.2023 19:31, Miquel Raynal wrote: >> > Hi Rafał, >> > >> > rafal@milecki.pl wrote on Wed, 08 Mar 2023 19:12:32 +0100: >> > >> >> On 2023-03-08 19:06, Miquel Raynal wrote: >> >>> Hi Rafał, >> >>> >> >>> rafal@milecki.pl wrote on Wed, 08 Mar 2023 17:55:46 +0100: >> >>> >>>> On 2023-03-08 17:34, Miquel Raynal wrote: >> >>>>> Hi Rafał, >> >>>>> >> >>>>> zajec5@gmail.com wrote on Fri, 24 Feb 2023 08:29:03 +0100: >> >>>>> >>>>>> From: Rafał Miłecki <rafal@milecki.pl> >> >>>>>>>> NVMEM subsystem looks for fixed NVMEM cells (specified in DT) by >> >>>>>> default. This behaviour made sense in early days before adding support >> >>>>>> for dynamic cells. >> >>>>>>>> With every new supported NVMEM device with dynamic cells current >> >>>>>> behaviour becomes non-optimal. It results in unneeded iterating over >> DT >> >>>>>> nodes and may result in false discovery of cells (depending on used DT >> >>>>>> properties). >> >>>>>>>> This behaviour has actually caused a problem already with the MTD >> >>>>>> subsystem. MTD subpartitions were incorrectly treated as NVMEM cells. >> >>>>> >> >>>>> That's true, but I expect this to be really MTD specific. >> >>>>> >> >>>>> A concrete proposal below. >> >>>>> >>>>>> Also with upcoming support for NVMEM layouts no new binding or driver >> >>>>>> should support fixed cells defined in device node. >> >>>>> >> >>>>> I'm not sure I agree with this statement. We are not preventing new >> >>>>> binding/driver to use fixed cells, or...? We offer a new way to expose >> >>>>> nvmem cells with another way than "fixed-offset" and "fixed-size" OF >> >>>>> nodes. >> >>>>>> From what I understood all new NVMEM bindings should have cells >> defined >> >>>> in the nvmem-layout { } node. That's what I mean by saying they should >> >>>> not be defined in device node (but its "nvmem-layout" instead). >> >>> >> >>> Layouts are just another possibility, either you user the nvmem-cells >> >>> compatible and produce nvmem cells with fixed OF nodes, or you use the >> >>> nvmem-layout container. I don't think all new bindings should have >> >>> cells in layouts. It depends if the content is static or not. >> >>> >>>>>> Solve this by modifying drivers for bindings that support specifying >> >>>>>> fixed NVMEM cells in DT. Make them explicitly tell NVMEM subsystem to >> >>>>>> read cells from DT. >> >>>>>>>> It wasn't clear (to me) if rtc and w1 code actually uses fixed cells. >> I >> >>>>>> enabled them to don't risk any breakage. >> >>>>>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >> >>>>>> [for drivers/nvmem/meson-{efuse,mx-efuse}.c] >> >>>>>> Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> >> >>>>>> --- >> >>>>>> V2: Fix stm32-romem.c typo breaking its compilation >> >>>>>> Pick Martin's Acked-by >> >>>>>> Add paragraph about layouts deprecating use_fixed_of_cells >> >>>>>> --- >> >>>>>> drivers/mtd/mtdcore.c | 2 ++ >> >>>>>> drivers/nvmem/apple-efuses.c | 1 + >> >>>>>> drivers/nvmem/core.c | 8 +++++--- >> >>>>>> drivers/nvmem/imx-ocotp-scu.c | 1 + >> >>>>>> drivers/nvmem/imx-ocotp.c | 1 + >> >>>>>> drivers/nvmem/meson-efuse.c | 1 + >> >>>>>> drivers/nvmem/meson-mx-efuse.c | 1 + >> >>>>>> drivers/nvmem/microchip-otpc.c | 1 + >> >>>>>> drivers/nvmem/mtk-efuse.c | 1 + >> >>>>>> drivers/nvmem/qcom-spmi-sdam.c | 1 + >> >>>>>> drivers/nvmem/qfprom.c | 1 + >> >>>>>> drivers/nvmem/rave-sp-eeprom.c | 1 + >> >>>>>> drivers/nvmem/rockchip-efuse.c | 1 + >> >>>>>> drivers/nvmem/sc27xx-efuse.c | 1 + >> >>>>>> drivers/nvmem/sprd-efuse.c | 1 + >> >>>>>> drivers/nvmem/stm32-romem.c | 1 + >> >>>>>> drivers/nvmem/sunplus-ocotp.c | 1 + >> >>>>>> drivers/nvmem/sunxi_sid.c | 1 + >> >>>>>> drivers/nvmem/uniphier-efuse.c | 1 + >> >>>>>> drivers/nvmem/zynqmp_nvmem.c | 1 + >> >>>>>> drivers/rtc/nvmem.c | 1 + >> >>>>>> drivers/w1/slaves/w1_ds250x.c | 1 + >> >>>>>> include/linux/nvmem-provider.h | 2 ++ >> >>>>>> 23 files changed, 29 insertions(+), 3 deletions(-) >> >>>>>>>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c >> >>>>>> index 0feacb9fbdac..1bb479c0f758 100644 >> >>>>>> --- a/drivers/mtd/mtdcore.c >> >>>>>> +++ b/drivers/mtd/mtdcore.c >> >>>>>> @@ -523,6 +523,7 @@ static int mtd_nvmem_add(struct mtd_info *mtd) >> >>>>>> config.dev = &mtd->dev; >> >>>>>> config.name = dev_name(&mtd->dev); >> >>>>>> config.owner = THIS_MODULE; >> >>>>>> + config.use_fixed_of_cells = of_device_is_compatible(node, >> "nvmem-cells"); >> >>>>> >> >>>>> I am wondering how mtd specific this is? For me all OF nodes containing >> >>>>> the nvmem-cells compatible should be treated as cells providers and >> >>>>> populate nvmem cells as for each children. >> >>>>> >> >>>>> Why don't we just check for this compatible to be present? in >> >>>>> nvmem_add_cells_from_of() ? And if not we just skip the operation. >> >>>>> >> >>>>> This way we still follow the bindings (even though using nvmem-cells in >> >>>>> the compatible property to require cells population was a mistake in >> >>>>> the first place, as discussed in the devlink thread recently) but there >> >>>>> is no need for a per-driver config option? >> >>>>>> This isn't mtd specific. Please check this patch for all occurrences >> of >> >>>> the: >> >>>> use_fixed_of_cells = true >> >>>>>> The very first one: drivers/nvmem/apple-efuses.c driver for the >> >>>> "apple,efuses" binding. That binding supports fixed OF cells, see: >> >>>> Documentation/devicetree/bindings/nvmem/apple,efuses.yaml >> >>> >> >>> I'm saying: based on what has been enforced so far, I would expect all >> >>> fixed cell providers to come with nvmem-cells as compatible, no? >> >>> >> >>> If that's the case we could use that as a common denominator? >> >> >> >> Sorry, I don't get it. Have you checked >> >> Documentation/devicetree/bindings/nvmem/apple,efuses.yaml >> >> ? >> >> >> >> It's a NVMEM provied binding with fixed cells that doesn't use >> >> nvmem-cells as compatible. There are many more. >> > >> > Oh yeah you're right, I'm mixing things. Well I guess you're right >> > then, it's such a mess, we have to tell the core the parsing method. >> > >> > So maybe another question: do we have other situations than mtd which >> > sometimes expect the nvmem core to parse the OF nodes to populate cells, >> > and sometimes not? >> >> I'm not aware of that. Please also check my patch. The only case I set >> "use_fixed_of_cells" conditionally is mtd code. In other cases it's >> hardcoded to "true". >> >> >> > Also, what about "of_children_are_cells" ? Because actually in most >> > cases it's a "fixed of cell", so I don't find the current naming >> > descriptive enough for something so touchy. >> >> That would be just incorrect because this new config property >> ("use_fixed_of_cells") is only about FIXED cells. >> >> There are cases of OF children being cells but NOT being fixed cells. >> They should NOT be parsed by the nvmem_add_cells_from_of(). >> >> Example: >> a607a850ba1f ("dt-bindings: nvmem: u-boot,env: add basic NVMEM cells") >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a607a850ba1fa966cbb035544c1588e24a6307df > > This is backwards. That's why layouts have been proposed: having > a clear framework were the nvmem core should or should not play with > the OF children nodes. If each binding is different, you end up with > the mess we have today, where nobody knows how to properly > populate the cells. > > Anyway, it's not a big deal either, if the cells are empty we can > easily check that and have *yet another* specific case in the core. > >> So that would result in U-Boot env: >> 1. Having OF children nodes being cells >> 2. Setting "of_children_are_cells" to false (counter-intuitive) to >> avoid nvmem_add_cells_from_of() > > Agreed. So what about config.ignore_of_children? > - mtd sets this to !is_compatible(nvmem-cells) > - nobody else touches it (the core don't try to parse the cell if it's > empty so U-Boot env driver works)
"ignore_of_children" would have opposite (reversed) meaning to the "use_fixed_of_cells": 1. By default it would be 0 / false 2. By default NVMEM code would NOT ignore OF children nodes
That is what I actually *don't* want.
Having NVMEM core look for fixed cells in device node is undesirable. I want that feature to be off by default. I want devices to have to enable it explicitly only when it's needed.
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