Messages in this thread | | | Date | Thu, 9 Mar 2023 07:56:05 +0100 | Subject | Re: [PATCH V2] nvmem: add explicit config option to read OF fixed cells | From | Rafał Miłecki <> |
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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
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()
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