Messages in this thread |  | | From | Saravana Kannan <> | Date | Wed, 14 Dec 2022 13:53:54 -0800 | Subject | Re: nvmem-cells regression after adding 'call of_platform_populate() for MTD partitions' |
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On Tue, Dec 13, 2022 at 8:54 AM Miquel Raynal <miquel.raynal@bootlin.com> wrote: > > Hi Maxim, > > bigunclemax@gmail.com wrote on Tue, 13 Dec 2022 14:02:34 +0300: > > > I looked closer at commit 658c4448bbbf and bcdf0315a61a, 5db1c2dbc04c16 commits. > > Looks like we have two different features binded to one property - "compatible". > > > > From one side it is the ability to forward the subnode of the mtd > > partition to the nvmem subsystem (658c4448bbbf and ac42c46f983e). > > And from another side is the ability to use custom initialization of > > the mtd partition (bcdf0315a61a and 5db1c2dbc04c16). > > > > What I mean: > > According to ac42c46f983e I can create DT like this: > > - | > > partitions { > > compatible = "fixed-partitions"; > > #address-cells = <1>; > > #size-cells = <1>; > > > > partition@0 { > > compatible = "nvmem-cells"; > > reg = <0x40000 0x10000>; > > #address-cells = <1>; > > #size-cells = <1>; > > macaddr_gmac1: macaddr_gmac1@0 { > > reg = <0x0 0x6>; > > }; > > }; > > }; > > > > > > And according to 5db1c2dbc04c16 I can create DT like this: > > - | > > partitions { > > compatible = "fixed-partitions"; > > #address-cells = <1>; > > #size-cells = <1>; > > > > partition@0 { > > compatible = "u-boot,env"; > > reg = <0x40000 0x10000>; > > }; > > }; > > > > But I can not use them both, because only one "compatible" property allowed. > > This will be incorrect: > > - | > > partitions { > > compatible = "fixed-partitions"; > > #address-cells = <1>; > > #size-cells = <1>; > > > > partition@0 { > > compatible = "u-boot,env"; # from ac42c46f983e > > compatible = "nvmem-cells"; # from 5db1c2dbc04c > > What about: > > compatible = "u-boot,env", "nvmem-cells"; > > instead? that should actually work. > > > reg = <0x40000 0x10000>; > > #address-cells = <1>; > > #size-cells = <1>; > > macaddr_gmac1: macaddr_gmac1@0 { > > reg = <0x0 0x6>; > > }; > > }; > > }; > > > > > compatible: Duplicate property name > > > > вт, 13 дек. 2022 г. в 12:46, Miquel Raynal <miquel.raynal@bootlin.com>: > > > > > > Hi Maxim, > > > > > > fido_max@inbox.ru wrote on Mon, 12 Dec 2022 20:57:49 +0300: > > > > > > > Hi, Miquel! > > > > > > > > On 12.12.2022 19:37, Miquel Raynal wrote: > > > > > > > > > Let me try to recap the situation for all the people I just involved: > > > > > > > > > > * An Ethernet driver gets its mac address from an nvmem cell. The > > > > > Ethernet controller DT node then has an "nvmem-cells" property > > > > > pointing towards an nvmem cell. > > > > > * The nvmem cell comes from an mtd partition. > > > > > * The mtd partition is flagged with a particular compatible > > > > > (which is also named "nvmem-cells") to tell the kernel that the node > > > > > produces nvmem cells. > > > > > * The mtd partition itself has no driver, but is the child node of a > > > > > "partitions" container which has one (in this case, > > > > > "fixed-partitions", see the snippet below). > > > > > > > > > > Because the "nvmem-cells" property of the Ethernet node points at the > > > > > nvmem-cell node, the core create a device link between the Ethernet > > > > > controller (consumer) and the mtd partition (producer). > > > > > > > > > > The device link in this case will never be satisfied because no driver > > > > > matches the "nvmem-cells" compatible of the partition node. > > > > > > > > > > Reverting commit bcdf0315a61a ("mtd: call of_platform_populate() for MTD > > > > > partitions") would IMHO not make much sense, the problem comes from the > > > > > device link side and even there, there is nothing really "wrong", > > > > > because I really expect the mtd device to be ready before the > > > > > Ethernet controller probe, the device link is legitimate. > > > > > > > > > > So I would like to explore other alternatives. Here are a bunch of > > > > > ideas, but I'm open: > > > > > > > > How about to create simple driver with compatible="nvmem-cell" and to move all the suff from main mtd driver which serves nvmem-cell to the probe function? > > > > > > This is probably worth the try but I doubt you can make it work without > > > regressions because IIRC the nvmem registration happens no matter the > > > compatible (not mentioning the user-otp and factory-otp cases). You can > > > definitely try this out if you think you can come up with something > > > though. > > > > > > But I would like to hear from the device-link gurus :) because even if > > > we fix mtd with a "trick" like above, I guess we'll very likely find > > > other corner cases like that and I am interested in understanding the > > > rationale of what could be a proper fix. > > >
Responding to the whole thread.
I'm going by Miquel's first email in which he cc'ed me and haven't actually looked at the mtd code. Couple of comments:
Independent of mtd/nvmem-cell, I generally frown on having a compatible string for a child node that you don't treat as a device. Even more so if you actually create a struct device for it and then don't do anything else with it. That's just a waste of memory. So, in general try to avoid that in the future if you can.
Also, there are flags the parent device's driver can set that'll tell fw_devlink not to treat a specific DT node as a real device. So, if we really need that I'll dig up and suggest a fix.
Lastly and more importantly, I've a series[1] that stops depending on the compatible property for fw_devlink to work. So it should be smarter than it is today. But that series has known bugs for which I gave test fixes in that thread. I plan to make a v2 of that series with that fix and I'm expecting it'll fix a bunch of fw_devlink issues.
Feel free to give v1 + squashing the fixes a shot if you are excited to try it. Otherwise, I'll try my best to get around to it this week (kinda swamped though + holidays coming up, so no promises).
[1] - https://lore.kernel.org/lkml/20220810060040.321697-1-saravanak@google.com/
Thanks, Saravana
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