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Date:	Sat, 19 Dec 2015 07:39:26 -0400
From:	Julian Margetson <runaway@...dw.ms>
To:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Måns Rullgård <mans@...sr.com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find
 dma channel

On 12/18/2015 10:34 PM, Andy Shevchenko wrote:
> On Sat, Dec 19, 2015 at 1:16 AM, Måns Rullgård <mans@...sr.com> wrote:
>> Julian Margetson <runaway@...dw.ms> writes:
>>
>>> On 12/18/2015 6:33 PM, Måns Rullgård wrote:
>>>> Julian Margetson <runaway@...dw.ms> writes:
>>>>
>>>>> On 12/18/2015 1:18 PM, Måns Rullgård wrote:
>>>>>> Julian Margetson <runaway@...dw.ms> writes:
>>>>>>
>>>>>>> On 12/18/2015 8:49 AM, Måns Rullgård wrote:
>>>>>>>> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> writes:
>>>>>>>>
>>>>>>>>>>> [    5.206125] Unable to handle kernel paging request for data at
>>>>>>>>>>> address 0x00000000
>>>>>>>>>>> [    5.228546] Faulting instruction address: 0xc043a2c8
>>>>>>>>>>> [    5.248577] Vector: 300 (Data Access) at [eddafae0]
>>>>>>>>>>> [    5.268658]     pc: c043a2c8: sata_dwc_qc_issue+0xb8/0x204
>>>>>>>>>> Well, that's not good.  Can you translate that address to a line of
>>>>>>>>>> code?
>>>>>>>>> Besides that, can you enable DYNAMIC_DEBUG in the config and append
>>>>>>>>> 'dw_dmac_core.dyndbg dw_dmac.dyndbg' to the kernel cmdline?
>>>>>>>> Enabling debug messages in the sata_dwc driver might also be informative.
>>>>>>>>
>>>>>>> Changed the sata-dwc to a module .
>>>>>>>
>>>>>>> [   18.475140] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>>>>>> [   18.535698] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>>>>> That's strange.  The only way that can happen is if
>>>>>> dmaengine_prep_slave_sg() return NULL, and that really shouldn't be
>>>>>> happening.  Did you turn on debug messages in dw_dma?  You can enable
>>>>>> some extra debug messages by adding "#define VERBOSE_DEBUG" at the top
>>>>>> of drivers/dma/dw/core.c
>>>>>>
>>>>> [   17.526173] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>>>> [   17.600124] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>>>> [   17.662978] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>>> Could you post the entire kernel log?  There might be important
>>>> information before the errors start.
>>>>
>>>
>>> =~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2015.12.18 15:01:48 =~=~=~=~=~=~=~=~=~=~=~=
>>> [    0.000000] Using Canyonlands machine description
>>> [    0.000000] Initializing cgroup subsys cpu
>>> [    0.000000] Linux version 4.4.0-rc5-Sam460ex (root@...ian-VirtualBox) (gcc version 4.8.2 (Ubuntu 4.8.2-16ubuntu3) ) #8 PREEMPT Fri Dec 18 13:36:34 AST 2015
>>> [    0.000000] Zone ranges:
>>> [    0.000000]   DMA      [mem 0x0000000000000000-0x000000002fffffff]
>>> [    0.000000]   Normal   empty
>>> [    0.000000]   HighMem  [mem 0x0000000030000000-0x000000007fffffff]
>>> [    0.000000] Movable zone start for each node
>>> [    0.000000] Early memory node ranges
>>> [    0.000000]   node   0: [mem 0x0000000000000000-0x000000007fffffff]
>>> [    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000007fffffff]
>>> [    0.000000] MMU: Allocated 1088 bytes of context maps for 255 contexts
>>> [    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 522752
>>> [    0.000000] Kernel command line: root=/dev/sda8 console=ttyS0,115200 console=tty0 dw_dmac_core.dyndbg dw_dmac.dyndbg
> I would suggest to use console=tty1 instead of console=tty0.
>
>> [...]
>>
>>> [   13.643415] systemd[1]: Mounted Configuration File System.
>>> [   17.526173] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>> [   17.600124] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>>> [   17.662978] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: dma_dwc_xfer_setup returns NULL
>> This log is weird.  The sata_dwc_probe() function prints several things
>> (one using dev_notice()), for instance this:
>>
>>          /* Read the ID and Version Registers */
>>          idr = in_le32(&hsdev->sata_dwc_regs->idr);
>>          versionr = in_le32(&hsdev->sata_dwc_regs->versionr);
>>          dev_notice(&ofdev->dev, "id %d, controller version %c.%c%c\n",
>>                     idr, ver[0], ver[1], ver[2]);
>>
>> The dw_dma_probe() function also prints a line:
>>
>>          dev_info(chip->dev, "DesignWare DMA Controller, %d channels\n",
>>                   pdata->nr_channels);
>>
>> These messages are nowhere to be seen in your log, nor are numerous
>> others that really must appear before before sata_dwc_qc_prep_by_tag()
>> can be called.
>>
> It would be better to add 'ignore_loglevel' to the cmdline as well.
>
>> I'd like to note that the driver works on my Sigma Designs based system
>> using a different DMA controller, so it's not completely broken.  The
>> DMA driver could still be faulty, but that still doesn't explain the
>> missing kernel messages.
>>
>> --
>> Måns Rullgård
>> --
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>
>


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