Re: [RESEND PATCH v3 5/8] mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel

[Jan Kiszka <jan.kiszka@xxxxxxxxxxx>]

On 24.08.20 19:20, Jan Kiszka wrote:
> On 24.08.20 14:49, Jan Kiszka wrote:
>> On 24.08.20 13:45, Vignesh Raghavendra wrote:
>>>
>>>
>>> On 8/22/20 11:35 PM, Jan Kiszka wrote:
>>>> On 01.06.20 09:04, Vignesh Raghavendra wrote:
>>>>> dma_request_chan_by_mask() can throw EPROBE_DEFER if DMA provider
>>>>> is not yet probed. Currently driver just falls back to using PIO mode
>>>>> (which is less efficient) in this case. Instead return probe deferral
>>>>> error as is so that driver will be re probed once DMA provider is
>>>>> available.
>>>>>
>>>>> Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
>>>>> Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
>>>>> ---
>>> [...]
>>>>>
>>>>>  static const struct spi_nor_controller_ops cqspi_controller_ops = {
>>>>> @@ -1269,8 +1274,11 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi, struct device_node *np)
>>>>>  			dev_dbg(nor->dev, "using direct mode for %s\n",
>>>>>  				mtd->name);
>>>>>
>>>>> -			if (!cqspi->rx_chan)
>>>>> -				cqspi_request_mmap_dma(cqspi);
>>>>> +			if (!cqspi->rx_chan) {
>>>>> +				ret = cqspi_request_mmap_dma(cqspi);
>>>>> +				if (ret == -EPROBE_DEFER)
>>>>> +					goto err;
>>>>> +			}
>>>>>  		}
>>>>>  	}
>>>>>
>>>>>
>>>>
>>>> This seem to break reading the SPI flash on our IOT2050 [1] (didn't test
>>>> the eval board yet).
>>>>
>>>> Without that commit, read happens via PIO, and that works. With the
>>>> commit, the pattern
>>>>
>>>> with open("out.bin", "wb") as out:
>>>>     pos = 0
>>>>     while pos < 2:
>>>>         with open("/dev/mtd0", "rb") as mtd:
>>>>            mtd.seek(pos * 0x10000)
>>>>            out.write(mtd.read(0x10000))
>>>>         pos += 1
>>>>
>>>> gives the wrong result for the second block while
>>>
>>> Interesting... Could you please explain wrong result? Is the data move
>>> around or completely garbage?
>>
>> It looks like some stripes contain data from other parts of the flash or
>> kernel RAM. It's not just garbage, there are readable strings included.
>>
>>>
>>> Does this fail even on AM654 EVM? Could you share full script for me to
>>> test locally?
>>
>> The scripts are complete (python). Just binary-diff the outputs.
>>
>> I'll try on the EVM later.
> 
> Done so now, could reproduce.

..."could *not* reproduce" there. Sorry if that caused confusion.

> 
> But the OSPIs are definitely different. EVM reports
> 
> spi-nor spi0.0: mt35xu512aba (65536 Kbytes)
> 
> with 4K erase size. Our our board, we have
> 
> spi-nor spi7.0: w25q128 (16384 Kbytes)
> 
> with 64K erase size.
> 
> Here is some extract of the hex-diffs between out.bin and out2.bin (the 
> latter being the good one):
> 
> --- /dev/fd/63  2020-08-24 17:16:58.776409282 +0000
> +++ /dev/fd/62  2020-08-24 17:16:58.776409282 +0000
> @@ -6,18 +6,18 @@
>  00000050  0f 30 0d 06 03 55 04 07  0c 06 44 61 6c 6c 61 73  |.0...U....Dallas|
>  00000060  31 27 30 25 06 03 55 04  0a 0c 1e 54 65 78 61 73  |1'0%..U....Texas|
>  00000070  20 49 6e 73 74 72 75 6d  65 6e 74 73 20 49 6e 63  | Instruments Inc|
> -00000080  84 8b 96 2c 0c 12 18 03  01 05 05 04 01 02 00 00  |...,............|
> -00000090  07 06 44 45 20 01 0d 14  2a 01 00 32 05 24 30 48  |..DE ...*..2.$0H|
> -000000a0  60 6c 30 14 01 00 00 0f  ac 04 01 00 00 0f ac 04  |`l0.............|
> -000000b0  01 00 00 0f ac 02 0c 00  2d 1a 6f 18 17 ff ff ff  |........-.o.....|
> +00000080  6f 72 70 6f 72 61 74 65  64 31 13 30 11 06 03 55  |orporated1.0...U|
> +00000090  04 0b 0c 0a 50 72 6f 63  65 73 73 6f 72 73 31 13  |....Processors1.|
> +000000a0  30 11 06 03 55 04 03 0c  0a 54 49 20 73 75 70 70  |0...U....TI supp|
> +000000b0  6f 72 74 31 1d 30 1b 06  09 2a 86 48 86 f7 0d 01  |ort1.0...*.H....|
>  000000c0  09 01 16 0e 73 75 70 70  6f 72 74 40 74 69 2e 63  |....support@ti.c|
>  000000d0  6f 6d 30 1e 17 0d 32 30  30 37 32 32 31 31 30 30  |om0...2007221100|
>  000000e0  30 30 5a 17 0d 32 30 30  38 32 31 31 31 30 30 30  |00Z..20082111000|
>  000000f0  30 5a 30 81 9d 31 0b 30  09 06 03 55 04 06 13 02  |0Z0..1.0...U....|
> -00000100  00 00 27 a4 00 00 42 43  5e 00 62 32 2f 00 b4 96  |..'...BC^.b2/...|
> -00000110  24 44 0c 00 c6 00 43 0a  00 00 0b f0 43 a5 2a 01  |$D....C.....C.*.|
> -00000120  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> -*
> +00000100  55 53 31 0b 30 09 06 03  55 04 08 0c 02 54 58 31  |US1.0...U....TX1|
> +00000110  0f 30 0d 06 03 55 04 07  0c 06 44 61 6c 6c 61 73  |.0...U....Dallas|
> +00000120  31 27 30 25 06 03 55 04  0a 0c 1e 54 65 78 61 73  |1'0%..U....Texas|
> +00000130  20 49 6e 73 74 72 75 6d  65 6e 74 73 20 49 6e 63  | Instruments Inc|
>  00000140  6f 72 70 6f 72 61 74 65  64 31 13 30 11 06 03 55  |orporated1.0...U|
>  00000150  04 0b 0c 0a 50 72 6f 63  65 73 73 6f 72 73 31 13  |....Processors1.|
>  00000160  30 11 06 03 55 04 03 0c  0a 54 49 20 73 75 70 70  |0...U....TI supp|
> 
> [...]
> 
>  000017a0  02 8a e5 06 c8 8c e2 14  c2 8a e5 7c 01 00 ea ed  |...........|....|
>  000017b0  1f 8f e2 66 02 00 ea 5b  45 72 72 6f 72 5d 20 52  |...f...[Error] R|
> -000017c0  69 64 20 55 54 43 20 49  44 21 21 21 0a 00 00 5b  |id UTC ID!!!...[|
> -000017d0  45 72 72 6f 72 5d 20 49  6e 76 61 6c 69 64 20 50  |Error] Invalid P|
> -000017e0  65 65 72 20 43 68 61 6e  6e 65 6c 20 4e 75 6d 62  |eer Channel Numb|
> -000017f0  65 72 21 21 21 0a 00 41  73 73 65 72 74 69 6f 6e  |er!!!..Assertion|
> +000017c0  4d 20 41 6c 6c 6f 63 20  54 58 20 43 68 20 66 61  |M Alloc TX Ch fa|
> +000017d0  69 6c 65 64 21 21 21 0a  00 00 00 73 72 63 2f 75  |iled!!!....src/u|
> +000017e0  64 6d 61 5f 63 68 2e 63  00 00 00 75 74 63 49 6e  |dma_ch.c...utcIn|
> +000017f0  66 6f 20 21 3d 20 4e 55  4c 4c 5f 50 54 52 00 75  |fo != NULL_PTR.u|
>  00001800  74 63 49 64 20 3c 3d 20  55 44 4d 41 5f 4e 55 4d  |tcId <= UDMA_NUM|
>  00001810  5f 55 54 43 5f 49 4e 53  54 41 4e 43 45 00 00 72  |_UTC_INSTANCE..r|
> 

I've done [1] for now in order to make the OSPI usable again here. It
looks like reading an mtd device in one chunk (single read syscall) is
fine, ie. "dd if=/dev/mtd3 of=content2 bs=<sizeof-mtd3>", while reading
it in multiple chunks is problematic, e.g. "dd if=/dev/mtd3 of=content2
bs=4096". Interestingly, the deviation is already on the first block,
which may speak against a setup issue for a second transfer.

The content I've seen in the corrupted output may come from other parts
of the memory. I've found my WIFI SSID there, which is definitely not
part of our OSPI image.

Jan

[1]
https://github.com/siemens/linux/commit/0abc3696f89f3a89214e483f7216b54e1b2196cd

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