Re: [PATCH] mtd: nand: raw: qcom_nandc: Don't clear_bam_transaction on READID

Sricharan Ramabadhran
2022-02-24T07:33:43Z

Hi Konrad,

On 2/8/2022 10:15 PM, Konrad Dybcio wrote:
>
> On 4.02.2022 18:17, Sricharan Ramabadhran wrote:
>> On 2/2/2022 12:54 PM, Sricharan Ramabadhran wrote:
>>> Hi Konrad/Miquel,
>>>
>>> On 2/1/2022 9:21 PM, Konrad Dybcio wrote:
>>>> On 01/02/2022 14:52, Miquel Raynal wrote:
>>>>> Hi Konrad,
>>>>>
>>>>> konrad.dybcio@somainline.org wrote on Mon, 31 Jan 2022 20:54:12 +0100:
>>>>>
>>>>>> On 31/01/2022 15:13, Sricharan Ramabadhran wrote:
>>>>>>> Hi Konrad,
>>>>>>>
>>>>>>> On 1/31/2022 3:39 PM, Konrad Dybcio wrote:
>>>>>>>> On 28/01/2022 18:50, Sricharan Ramabadhran wrote:
>>>>>>>>> Hi Konrad,
>>>>>>>>>
>>>>>>>>> On 1/28/2022 9:55 AM, Sricharan Ramabadhran wrote:
>>>>>>>>>> Hi Miquel,
>>>>>>>>>>
>>>>>>>>>> On 1/26/2022 4:12 PM, Miquel Raynal wrote:
>>>>>>>>>>> Hi Mani,
>>>>>>>>>>>
>>>>>>>>>>> mani@kernel.org wrote on Wed, 26 Jan 2022 16:03:16 +0530:
>>>>>>>>>>>> On Wed, Jan 26, 2022 at 11:16:13AM +0100, Miquel Raynal wrote:
>>>>>>>>>>>>> Hello,
>>>>>>>>>>>>>
>>>>>>>>>>>>> miquel.raynal@bootlin.com wrote on Fri, 14 Jan 2022 08:27:18 +0100:
>>>>>>>>>>>>>> Hi Konrad,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> konrad.dybcio@somainline.org wrote on Thu, 13 Jan 2022 19:44:26 >>>>>>>> +0100:
>>>>>>>>>>>>>>> While I have absolutely 0 idea why and how, running >>>>>>>>> clear_bam_transaction
>>>>>>>>>>>>>>> when READID is issued makes the DMA totally clog up and refuse >>>>>>>>> to function
>>>>>>>>>>>>>>> at all on mdm9607. In fact, it is so bad that all the data >>>>>>>>> gets garbled
>>>>>>>>>>>>>>> and after a short while in the nand probe flow, the CPU >>>>>>>>> decides that
>>>>>>>>>>>>>>> sepuku is the only option.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Removing _READID from the if condition makes it work like a >>>>>>>>> charm, I can
>>>>>>>>>>>>>>> read data and mount partitions without a problem.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>> This is totally just an observation which took me an inhumane >>>>>>>>> amount of
>>>>>>>>>>>>>>> debug prints to find.. perhaps there's a better reason behind >>>>>>>>> this, but
>>>>>>>>>>>>>>> I can't seem to find any answers.. Therefore, this is a BIG RFC!
>>>>>>>>>>>>>> I'm adding two people from codeaurora who worked a lot on this >>>>>>>> driver.
>>>>>>>>>>>>>> Hopefully they will have an idea :)
>>>>>>>>>>>>> Sadre, I've spent a significant amount of time reviewing your >>>>>>> patches,
>>>>>>>>>>>>> now it's your turn to not take a month to answer to your peers
>>>>>>>>>>>>> proposals.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Please help reviewing this patch.
>>>>>>>>>>>> Sorry. I was hoping that Qcom folks would chime in as I don't >>>>>> have any idea
>>>>>>>>>>>> about the mdm9607 platform. It could be that the mail server >>>>>> migration from
>>>>>>>>>>>> codeaurora to quicinc put a barrier here.
>>>>>>>>>>>>
>>>>>>>>>>>> Let me ping them internally.
>>>>>>>>>>> Oh, ok, I didn't know. Thanks!
>>>>>>>>>>     Sorry Miquel, somehow we did not get this email in our inbox.
>>>>>>>>>>     Thanks to Mani for pinging us, we will test this up today and >>>> get back.
>>>>>>>>>        While we could not reproduce this issue on our ipq boards (do >>> not have a mdm9607 right now) and
>>>>>>>>>         issue does not look any obvious.
>>>>>>>>>        can you please give the debug logs that you did for the above >>> stage by stage ?
>>>>>>>> I won't have access to the board for about two weeks, sorry.
>>>>>>>>
>>>>>>>> When I get to it, I'll surely try to send you the logs, though there
>>>>>>>>
>>>>>>>> wasn't much more than just something jumping to who-knows-where
>>>>>>>>
>>>>>>>> after clear_bam_transaction was called, resulting in values >> associated with
>>>>>>>>
>>>>>>>> the NAND being all zeroed out in pr_err/_debug/etc.
>>>>>>>>
>>>>>>>      Ok sure. So was the READID command itself failing (or) the > subsequent one ?
>>>>>>>     We can check which parameter reset by the clear_bam_transaction is > causing the
>>>>>>>     failure.  Meanwhile, looping in Pradeep who has access to the > board, so in a better
>>>>>>>     position to debug.
>>>>>> I'm sorry I have so few details on hand, and no kernel tree (no access to that machine either, for now).
>>>>>>
>>>>>>
>>>>>> I will try to describe to the best of my abilities what I recall.
>>>>>>
>>>>>>
>>>>>> My methodology of making sure things don't go haywire was to print the oob size
>>>>>>
>>>>>> of our NAND basically every two lines of code (yes, i was very desperate at one point),
>>>>>>
>>>>>> as that was zeroed out when *the bug* happened,
>>>>> This does look like a pointer error at some point and some kernel data
>>>>> has been corrupted very badly by the driver.
>>>>>
>>>>>> leading to a kernel bug/panic/stall
>>>>>>
>>>>>> (can't recall what exactly it was, but it said something along the lines of "no support for
>>>>>>
>>>>>> oob size 0" and then it didn't fail graceully, leading to some bad jumps and ultimately
>>>>>>
>>>>>> a dead platform..)
>>>>>>
>>>>>>
>>>>>> after hours of digging, I found out that everything goes fine until clear_bam_transaction is called,
>>>>> Do you remember if this function was called for the first time when
>>>>> this happened?
>>>> I think so, if I recall correctly there are no more callers in this path, as readid is the first nand command executed in flash probe flow.
>>>>
>>>>
>>>>
>>>>>> after that gets executed every nand op starts reading all zeroes (for example in JEDEC ID check)
>>>>>>
>>>>>> so I added the changes from this patch, and things magically started working... My suspicion is
>>>>>>
>>>>>> that the underlying FIFO isn't fully drained (is it a FIFO on 9607? bah, i work on too many socs at once)
>>>>> I don't see it in the list of supported devices, what's the exact
>>>>> compatible used?
>>>> qcom,ipq4019-nand
>>>>
>>>>
>>>>
>>>>>> and this function only makes Linux think it is, without actually draining it, and the leftover
>>>>>>
>>>>>> commands get executed with some parts of them getting overwritten, resulting in the
>>>>>>
>>>>>> famous garbage in - garbage out situation, but that's only a guesstimate..
>>>>> I would bet for a non allocated bam-ish pointer that is reset to zero
>>>>> in the clear_bam_transaction() helper.
>>>>>
>>>>> Can you get your hands on the board again?
>>>> Sure, but as I mentioned previously, only in about 2 weeks, I can't really do any dev before then.. :(
>>>>
>>>>
>>>>
>>>>> It would be nice to check if the allocation always occurs before use,
>>>>> and if yes on how much bytes.
>>>>>
>>>>> If the pointer is not dangling, then perhaps something else smashes
>>>>> that pointer.
>>>>
>>>> Konrad
>>>>
>>>>>> Do note this somehow worked fine on 5.11 and then broke on 5.12/13. I went as far as replacing most
>>>>>>
>>>>>> of the kernel with the updated/downgraded parts via git checkout (i tried many combinations),
>>>>>>
>>>>>> to no avail.. I even tried different compilers and optimization levels, thinking it could have been
>>>>>>
>>>>>> a codegen issue, but no luck either.
>>>>>>
>>>>>>
>>>>>> I.. do understand this email is a total mess to read, as much as it was to write, but
>>>>>>
>>>>>> without access to my code and the machine itself I can't give you solid details, and
>>>>>>
>>>>>> the fact this situation is far from ordinary doesn't help either..
>>>>>>
>>>>>>
>>>>>> The latest (ancient, not quite pretty, but probably working if my memory is correct) version of my patches
>>>>>>
>>>>>> for the mdm9607 is available at [1], I will push the new revision after I get access to the workstation.
>>>>>>
>>>   + few more who have access to the board.
>>>
>>>    Going by the description, for kernel corruption, we can try out a KASAN build.
>>>    Since you have mentioned it worked till 5.11, you bisected the driver till 5.11 head and it worked ?
>>>
>>    Tried running a KASAN enabled image on IPQ board, but no luck. Nothing came out.
>>    Only if someone with the board can help here, we can proceed
>>
>>
>> Regards,
>>   Sricharan
>>
> I have the board with me again. Please tell me where do we start :)

Sorry for the delayed response.

As a first step, Can you enable KASAN and check if you get any
warnings ?

Then, can you check inside clear_bam_transaction, which parameter
resetting specifically is causing the issue ?

Regards,
Sricharan