| Message ID | 20220825214423.903672-1-michael@walle.cc (mailing list archive) |
|---|---|
| Headers | show |
| Series | nvmem: core: introduce NVMEM layouts | expand |
On 25.08.2022 23:44, Michael Walle wrote: > This is now the third attempt to fetch the MAC addresses from the VPD > for the Kontron sl28 boards. Previous discussions can be found here: > https://lore.kernel.org/lkml/20211228142549.1275412-1-michael@walle.cc/ > > > NVMEM cells are typically added by board code or by the devicetree. But > as the cells get more complex, there is (valid) push back from the > devicetree maintainers to not put that handling in the devicetree. I dropped the ball waiting for Rob's reponse in the [PATCH 0/2] dt-bindings: nvmem: support describing cells https://lore.kernel.org/linux-arm-kernel/0b7b8f7ea6569f79524aea1a3d783665@walle.cc/T/ Before we go any further can we have a clear answer from Rob (or Krzysztof now too?): Is there any point in having bindings like: compatible = "mac-address"; for NVMEM cells nodes? So systems (Linux, U-Boot) can handle them in a more generic way? Or do we prefer more conditional drivers code (or layouts code as in this Michael's proposal) that will handle cells properly based on their names? I'm not arguing for any solution. I just want to make sure we choose the right way to proceed. > Therefore, introduce NVMEM layouts. They operate on the NVMEM device and > can add cells during runtime. That way it is possible to add complex > cells than it is possible right now with the offset/length/bits > description in the device tree. For example, you can have post processing > for individual cells (think of endian swapping, or ethernet offset > handling). You can also have cells which have no static offset, like the > ones in an u-boot environment. The last patches will convert the current > u-boot environment driver to a NVMEM layout and lifting the restriction > that it only works with mtd devices. But as it will change the required > compatible strings, it is marked as RFC for now. It also needs to have > its device tree schema update which is left out here. So do I get it right that we want to have: 1. NVMEM drivers for providing I/O access to NVMEM devices 2. NVMEM layouts for parsing & NVMEM cells and translating their content ? I guess it sounds good and seems to be a clean solution. One thing I believe you need to handle is replacing "cell_post_process" callback with your layout thing. I find it confusing to have 1. cell_post_process() CB at NVMEM device level 2. post_process() CB at NVMEM cell level > For now, the layouts are selected by a specifc compatible string in a > device tree. E.g. the VPD on the kontron sl28 do (within a SPI flash node): > compatible = "kontron,sl28-vpd", "user-otp"; > or if you'd use the u-boot environment (within an MTD patition): > compatible = "u-boot,env", "nvmem"; > > The "user-otp" (or "nvmem") will lead to a NVMEM device, the > "kontron,sl28-vpd" (or "u-boot,env") will then apply the specific layout > on top of the NVMEM device. > > NVMEM layouts as modules? > While possible in principle, it doesn't make any sense because the NVMEM > core can't be compiled as a module. The layouts needs to be available at > probe time. (That is also the reason why they get registered with > subsys_initcall().) So if the NVMEM core would be a module, the layouts > could be modules, too. > > Michael Walle (14): > net: add helper eth_addr_add() > of: base: add of_parse_phandle_with_optional_args() > nvmem: core: add an index parameter to the cell > nvmem: core: drop the removal of the cells in nvmem_add_cells() > nvmem: core: add nvmem_add_one_cell() > nvmem: core: introduce NVMEM layouts > nvmem: core: add per-cell post processing > dt-bindings: mtd: relax the nvmem compatible string > dt-bindings: nvmem: add YAML schema for the sl28 vpd layout > nvmem: layouts: add sl28vpd layout > nvmem: core: export nvmem device size > nvmem: layouts: rewrite the u-boot-env driver as a NVMEM layout > nvmem: layouts: u-boot-env: add device node > arm64: dts: ls1028a: sl28: get MAC addresses from VPD > > .../devicetree/bindings/mtd/mtd.yaml | 7 +- > .../nvmem/layouts/kontron,sl28-vpd.yaml | 52 +++++ > .../fsl-ls1028a-kontron-kbox-a-230-ls.dts | 8 + > .../fsl-ls1028a-kontron-sl28-var1.dts | 2 + > .../fsl-ls1028a-kontron-sl28-var2.dts | 4 + > .../fsl-ls1028a-kontron-sl28-var4.dts | 2 + > .../freescale/fsl-ls1028a-kontron-sl28.dts | 13 ++ > drivers/nvmem/Kconfig | 2 + > drivers/nvmem/Makefile | 1 + > drivers/nvmem/core.c | 183 +++++++++++---- > drivers/nvmem/imx-ocotp.c | 4 +- > drivers/nvmem/layouts/Kconfig | 22 ++ > drivers/nvmem/layouts/Makefile | 7 + > drivers/nvmem/layouts/sl28vpd.c | 144 ++++++++++++ > drivers/nvmem/layouts/u-boot-env.c | 147 ++++++++++++ > drivers/nvmem/u-boot-env.c | 218 ------------------ > include/linux/etherdevice.h | 14 ++ > include/linux/nvmem-consumer.h | 11 + > include/linux/nvmem-provider.h | 47 +++- > include/linux/of.h | 25 ++ > 20 files changed, 649 insertions(+), 264 deletions(-) > create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml > create mode 100644 drivers/nvmem/layouts/Kconfig > create mode 100644 drivers/nvmem/layouts/Makefile > create mode 100644 drivers/nvmem/layouts/sl28vpd.c > create mode 100644 drivers/nvmem/layouts/u-boot-env.c > delete mode 100644 drivers/nvmem/u-boot-env.c
Hi, Am 2022-08-28 17:05, schrieb Rafał Miłecki: > On 25.08.2022 23:44, Michael Walle wrote: >> This is now the third attempt to fetch the MAC addresses from the VPD >> for the Kontron sl28 boards. Previous discussions can be found here: >> https://lore.kernel.org/lkml/20211228142549.1275412-1-michael@walle.cc/ >> >> >> NVMEM cells are typically added by board code or by the devicetree. >> But >> as the cells get more complex, there is (valid) push back from the >> devicetree maintainers to not put that handling in the devicetree. > > I dropped the ball waiting for Rob's reponse in the > [PATCH 0/2] dt-bindings: nvmem: support describing cells > https://lore.kernel.org/linux-arm-kernel/0b7b8f7ea6569f79524aea1a3d783665@walle.cc/T/ > > Before we go any further can we have a clear answer from Rob (or > Krzysztof now too?): > > > Is there any point in having bindings like: > > compatible = "mac-address"; > > for NVMEM cells nodes? So systems (Linux, U-Boot) can handle them in a > more generic way? > > > Or do we prefer more conditional drivers code (or layouts code as in > this Michael's proposal) that will handle cells properly based on their > names? What do you mean by "based on their names?". > I'm not arguing for any solution. I just want to make sure we choose > the > right way to proceed. With the 'compatible = "mac-address"', how would you detect what kind of transformation you need to apply? You could guess ascii, yes. But swapping bytes? You cannot guess that. So you'd need additional information coming from the device tree. But Rob was quite clear that this shouldn't be in the device tree: | I still don't think trying to encode transformations of data into the DT | is right approach. https://lore.kernel.org/linux-devicetree/YaZ5JNCFeKcdIfu8@robh.at.kernel.org/ He also mention that the compatible should be on the nvmem device level and should use specific compatible strings: https://lore.kernel.org/linux-devicetree/CAL_JsqL55mZJ6jUyQACer2pKMNDV08-FgwBREsJVgitnuF18Cg@mail.gmail.com/ And IMHO that makes sense, because it matches the hardware and not any NVMEM cells which is the *content* of a memory device. And as you see in the sl28vpd layout, it allows you to do much more, like checking for integrity, and make it future proof by supporting different versions of this sl28vpd layout. What if you use it with the u-boot,env? You wouldn't need it because u-boot,env will already know how to interpret it as an ascii string (and it also know the offset). In this sense, u-boot,env is already a compatible string describing the content of a NVMEM device (and the compatible string is at the device level). >> Therefore, introduce NVMEM layouts. They operate on the NVMEM device >> and >> can add cells during runtime. That way it is possible to add complex >> cells than it is possible right now with the offset/length/bits >> description in the device tree. For example, you can have post >> processing >> for individual cells (think of endian swapping, or ethernet offset >> handling). You can also have cells which have no static offset, like >> the >> ones in an u-boot environment. The last patches will convert the >> current >> u-boot environment driver to a NVMEM layout and lifting the >> restriction >> that it only works with mtd devices. But as it will change the >> required >> compatible strings, it is marked as RFC for now. It also needs to have >> its device tree schema update which is left out here. > > So do I get it right that we want to have: > > 1. NVMEM drivers for providing I/O access to NVMEM devices > 2. NVMEM layouts for parsing & NVMEM cells and translating their > content > ? Correct. > I guess it sounds good and seems to be a clean solution. Good to hear :) > One thing I believe you need to handle is replacing "cell_post_process" > callback with your layout thing. > > I find it confusing to have > 1. cell_post_process() CB at NVMEM device level > 2. post_process() CB at NVMEM cell level What is wrong with having a callback at both levels? Granted, in this particular case (it is just used at one place), I still think that it is the wrong approach to add this transformation in the driver (in this particular case). The driver is supposed to give you access to the SoC's fuse box, but it will magically change the content of a cell if the nvmem consumer named this cell "mac-address" (which you also found confusing the last time and I do too!). The driver itself doesn't add any cells on its own, so I cannot register a .post_process hook there. Therefore, you'd need that post_process hook on every cell, which is equivalent to have a post_process hook at device level. Unless you have a better idea. I'll leave that up to NXP to fix that (or leave it like that). -michael
Thanks Michael for the work. On 29/08/2022 09:22, Michael Walle wrote: > >> One thing I believe you need to handle is replacing "cell_post_process" >> callback with your layout thing. >> >> I find it confusing to have >> 1. cell_post_process() CB at NVMEM device level >> 2. post_process() CB at NVMEM cell level > > What is wrong with having a callback at both levels? we should converge this tbh, its more than one code paths to deal with similar usecases. I have put down some thoughts in "[PATCH v1 06/14] nvmem: core: introduce NVMEM layouts" and "[PATCH v1 07/14] nvmem: core: add per-cell post processing" review. --srini > > Granted, in this particular case (it is just used at one place), I still > think that it is the wrong approach to add this transformation in the > driver (in this particular case). The driver is supposed to give you > access to the SoC's fuse box, but it will magically change the content > of a cell if the nvmem consumer named this cell "mac-address" (which > you also found confusing the last time and I do too!). > > The driver itself doesn't add any cells on its own, so I cannot register > a .post_process hook there. Therefore, you'd need that post_process hook > on every cell, which is equivalent to have a post_process hook at > device level. > > Unless you have a better idea. I'll leave that up to NXP to fix that (or > leave it like that). > > -michael
On 28/08/2022 18:05, Rafał Miłecki wrote: > On 25.08.2022 23:44, Michael Walle wrote: >> This is now the third attempt to fetch the MAC addresses from the VPD >> for the Kontron sl28 boards. Previous discussions can be found here: >> https://lore.kernel.org/lkml/20211228142549.1275412-1-michael@walle.cc/ >> >> >> NVMEM cells are typically added by board code or by the devicetree. But >> as the cells get more complex, there is (valid) push back from the >> devicetree maintainers to not put that handling in the devicetree. > > I dropped the ball waiting for Rob's reponse in the > [PATCH 0/2] dt-bindings: nvmem: support describing cells > https://lore.kernel.org/linux-arm-kernel/0b7b8f7ea6569f79524aea1a3d783665@walle.cc/T/ > > Before we go any further can we have a clear answer from Rob (or > Krzysztof now too?): > > > Is there any point in having bindings like: > > compatible = "mac-address"; > > for NVMEM cells nodes? So systems (Linux, U-Boot) can handle them in a > more generic way? I think Rob is already in the subject, but I wonder how would that work for U-Boot? You might have multiple cards, so how does this matching would work? IOW, what problem would it solve comparing to existing solution (alias to ethernet device with mac-address field)? Best regards, Krzysztof