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From: Marek Vasut <marex@denx.de>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Francesco Dolcini <francesco@dolcini.it>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org,
	Francesco Dolcini <francesco.dolcini@toradex.com>,
	Shawn Guo <shawnguo@kernel.org>,
	linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org,
	u-boot@lists.denx.de
Subject: Re: [PATCH v1] mtd: parsers: ofpart: Fix parsing when size-cells is 0
Date: Fri, 2 Dec 2022 16:23:29 +0100	[thread overview]
Message-ID: <223b7a4e-3aff-8070-7387-c77d2ded1dd6@denx.de> (raw)
In-Reply-To: <20221202160030.1b8d0b8a@xps-13>

On 12/2/22 16:00, Miquel Raynal wrote:
> Hi Marek,

Hi,

> marex@denx.de wrote on Fri, 2 Dec 2022 15:31:40 +0100:
> 
>> On 12/2/22 15:05, Miquel Raynal wrote:
>>> Hi Francesco,
>>
>> Hi,
>>
>> [...]
>>
>>> I still strongly disagree with the initial proposal but what I think we
>>> can do is:
>>>
>>> 1. To prevent future breakages:
>>>     Fix fdt_fixup_mtdparts() in u-boot. This way newer U-Boot + any
>>>     kernel should work.
>>>
>>> 2. To help tracking down situations like that:
>>>     Keep the warning in ofpart.c but continue to fail.
>>>
>>> 3. To fix the current situation:
>>>      Immediately revert commit (and prevent it from being backported):
>>>      753395ea1e45 ("ARM: dts: imx7: Fix NAND controller size-cells")
>>>      This way your own boot flow is fixed in the short term.
>>
>> Here I disagree, the fix is correct and I think we shouldn't
>> proliferate incorrect DTs which don't match the binding document.
> 
> I agree we should not proliferate incorrect DTs, so let's use a modern
> description then

Yes please !

> , with a controller and a child node which defines the
> chip.

But what if there is no chip connected to the controller node ?

If I understand the proposal here right (please correct me if I'm 
wrong), then:

1) This is the original, old, wrong binding:
&gpmi {
   #size-cells = <1>;
   ...
   partition@N { ... };
};


2) This is the newer, but still wrong binding:
&gpmi {
   #size-cells = <0>;
   ...
   partitions {
     partition@N { ... };
   };
};

3) This is the newest binding, what we want:
&gpmi {
   #size-cells = <0>;
   ...
   nand-chip {
     partitions {
       partition@N { ... };
     };
   };
};

But if there is no physical nand chip connected to the controller, would 
we end up with empty nand-chip node in DT, like this?
&gpmi {
   #size-cells = <X>;
   ...
   nand-chip { /* empty */ };
};
What would be the gpmi controller size cells (X) in that case, still 0, 
right ? So how does that help solve this problem, wouldn't U-Boot still 
populate the partitions directly under the gpmi node or into partitions 
sub-node ?

>> Rather, if a bootloader generates incorrect (new) DT entries, I
>> believe the driver should implement a fixup and warn user about this.
>> PC does that as well with broken ACPI tables as far as I can tell.
>>
>> I'm not convinced making a DT non-compliant with bindings again,
> 
> I am sorry to say so, but while warnings reported by the tools
> should be fixed, it's not because the tool does not scream at you that
> the description is valid. We are actively working on enhancing the
> schema so that "all" improper descriptions get warnings (see the series
> pointed earlier), but in no way this change makes the node compliant
> with modern bindings.
> 
> I'm not saying the fix is wrong, but let's be pragmatic, it currently
> leads to boot failures.

I fully agree that we do have a problem, and that it trickled into 
stable makes it even worse. Maybe I don't fully understand the thing 
with nand-chip proposal, see my question above, esp. the last part.

>> only to work around a problem induced by bootloader, is the right approach
>> here.
> 
> When a patch breaks a board and there is no straight fix, you revert
> it, then you think harder. That's what I am saying. This is a temporary
> solution.

Isn't this patch the straight fix, at least until the bootloader can be 
updated to generate the nand-chip node correctly ?

>> This would be setting a dangerous example, where anyone could request a DT fix to be reverted because their random bootloader does the wrong thing and with valid DT clean up, something broke.
> 
> Please, you know this is not valid DT clean up. We've been decoupling
> controller and chip description since 2016. What I am proposing is a
> valid DT cleanup, not to the latest standard, but way closer than the
> current solution.

I think I really need one more explanation of the nand-chip part above.

[...]

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  reply	other threads:[~2022-12-02 15:24 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-02  7:19 [PATCH v1] mtd: parsers: ofpart: Fix parsing when size-cells is 0 Francesco Dolcini
2022-12-02  9:14 ` Miquel Raynal
2022-12-02 10:12   ` Francesco Dolcini
2022-12-02 10:24     ` Francesco Dolcini
2022-12-02 10:53       ` Miquel Raynal
2022-12-02 11:23         ` Francesco Dolcini
2022-12-02 14:05           ` Miquel Raynal
2022-12-02 14:31             ` Marek Vasut
2022-12-02 15:00               ` Miquel Raynal
2022-12-02 15:23                 ` Marek Vasut [this message]
2022-12-02 15:49                   ` Miquel Raynal
2022-12-02 16:01                     ` Miquel Raynal
2022-12-02 16:17                     ` Marek Vasut
2022-12-02 16:42                       ` Miquel Raynal
2022-12-02 16:52                         ` Marek Vasut
2022-12-02 16:57                           ` Miquel Raynal
2022-12-02 17:08                             ` Marek Vasut
2022-12-05 11:26                               ` Francesco Dolcini
2022-12-05 13:49                                 ` Miquel Raynal
2022-12-05 16:25                                   ` Marek Vasut
2022-12-15  7:16                                     ` Miquel Raynal
2022-12-15  7:45                                       ` Marek Vasut
2022-12-15  8:04                                         ` Miquel Raynal
2022-12-16  0:36                                           ` Marek Vasut
2022-12-16  7:52                                             ` Francesco Dolcini
2022-12-16  7:45                                       ` Francesco Dolcini
2022-12-16 10:46                                         ` Marek Vasut
2022-12-16 11:01                                           ` Miquel Raynal
2022-12-16 12:37                                             ` Francesco Dolcini
2022-12-16 13:37                                               ` Miquel Raynal
2022-12-16 14:32                                                 ` Marek Vasut
2022-12-16 15:35                                                   ` Miquel Raynal
2022-12-16 16:30                                                     ` Francesco Dolcini
2023-01-02  9:40                                                       ` Miquel Raynal
2023-01-05 11:33                                                         ` Miquel Raynal
2023-01-05 12:47                                                           ` Francesco Dolcini
2023-01-05 14:51                                                             ` Marek Vasut
2023-01-05 15:03                                                               ` Miquel Raynal
2022-12-02 17:20                         ` Francesco Dolcini
2022-12-05 11:30                           ` Francesco Dolcini
2022-12-05 15:28                             ` Miquel Raynal
2022-12-02 16:45                       ` Francesco Dolcini
2022-12-02 17:05                         ` Miquel Raynal
2022-12-02 15:56               ` Thorsten Leemhuis
2022-12-04 12:50                 ` Marek Vasut
2022-12-04 12:59                   ` Thorsten Leemhuis
2022-12-04 15:50                     ` Marek Vasut
2022-12-02 12:43 ` Greg KH

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