Date:	Sun, 20 Dec 2015 18:49:34 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Julian Margetson <runaway@...dw.ms>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

Julian Margetson <runaway@...dw.ms> writes:

> On 12/20/2015 1:11 PM, Måns Rullgård wrote:
>> Julian Margetson <runaway@...dw.ms> writes:
>>
>>> On 12/19/2015 4:41 PM, Måns Rullgård wrote:
>>>> Andy Shevchenko <andy.shevchenko@...il.com> writes:
>>>>
>>>>> On Sat, Dec 19, 2015 at 10:16 PM, Julian Margetson <runaway@...dw.ms> wrote:
>>>>>> On 12/19/2015 3:07 PM, Måns Rullgård wrote:
>>>>>>> Julian Margetson <runaway@...dw.ms> writes:
>>>>>>>> Total pages: 522752
>>>>>>>> [    0.000000] Kernel command line: root=/dev/sda8 console=ttyS0,115200
>>>>>>>> console=tty1 dw_dmac_core.dyndbg dw_dmac.dyndbg
>>>>>>> Please add ignore_log_level.
>>>>>>>
>>>>>> Had to truncate the kernel command line to add it.
>>>>> I guess Måns meant 'ignore_loglevel'
>>>> Obviously.  I can never remember where the underscores go.
>>> [   18.362244] sd 3:0:0:0: [sdc] 976773168 512-byte logical blocks: (500 GB/465 GiB)
>>> [   18.372454] sd 3:0:0:0: Attached scsi generic sg3 type 0
>>> [   18.405433] sd 3:0:0:0: [sdc] Write Protect is off
>>> [   18.420654] sd 3:0:0:0: [sdc] Mode Sense: 00 3a 00 00
>>> [   18.461731] sd 3:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
>>> [   18.502918] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: port=0 dma dir=from device n_elem=1
>>> [   18.511807] dma dma0chan0: dwc_prep_slave_sg
>>> [   18.516083] dma dma0chan0: scanned 1 descriptors on freelist
>>> [   18.521753] sata-dwc 4bffd1000.sata: dma_dwc_xfer_setup sg: 0xedeaa800, count: 1 addr: 0xfffffffff6a14400
>>> [   18.531327] sata-dwc 4bffd1000.sata: sata_dwc_qc_issue: tag=0 ap->link.sactive = 0x00000001 sactive=0x00000001
>>> [   18.541359] sata-dwc 4bffd1000.sata: sata_dwc_exec_command_by_tag cmd(0x60): READ FPDMA QUEUED tag=0
>>> [   18.553703] sata-dwc 4bffd1000.sata: sata_dwc_isr intpr=0x00000082 active_tag=-84148995
>>> [   18.561717] sata-dwc 4bffd1000.sata: sata_dwc_isr: NEWFP tag=0
>>> [   18.567561] sata-dwc 4bffd1000.sata: sata_dwc_bmdma_start_by_tag qc=ed2340b8 tag: 0 cmd: 0x60 dma_dir: from device start_dma? 1
>>> [   18.579043] sata-dwc 4bffd1000.sata: taskfile cmd: 0x60 protocol: ATA NCQ flags: 0x17 device: 40
>>> [   18.587836] sata-dwc 4bffd1000.sata: feature: 0x08 nsect: 0x0 lbal: 0x0 lbam: 0x0 lbah: 0x0
>>> [   18.596196] sata-dwc 4bffd1000.sata: hob_feature: 0x00 hob_nsect: 0x0 hob_lbal: 0x0 hob_lbam: 0x0 hob_lbah: 0x0
>>> [   18.606292] dma dma0chan0: dwc_tx_submit: queued 2
>>> [   18.611091] dma dma0chan0: dwc_dostart_first_queued: started 2
>>> [   48.748614] ata3: lost interrupt (Status 0x40)
>> Now we're getting somewhere.  The dma transfer is set up and initiated,
>> but then nothing happens.  Comparing the old sata_dwc driver, from
>> before the switch to dmaengine, with the dw_dma driver, I noticed an
>> obvious problem: the descriptors are filled in using the wrong byte
>> order.  This patch might fix that.
>
> [   18.534844] ata3.00: configured for UDMA/133
> [   18.538182] scsi 3:0:0:0: Direct-Access     ATA      WDC WD5000AAKS-0 3B01 PQ: 0 ANSI: 5
> [   18.539025] sd 3:0:0:0: [sdc] 976773168 512-byte logical blocks: (500 GB/465 GiB)
> [   18.539236] sd 3:0:0:0: [sdc] Write Protect is off
> [   18.539245] sd 3:0:0:0: [sdc] Mode Sense: 00 3a 00 00
> [   18.539338] sd 3:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
> [   18.540049] sd 3:0:0:0: Attached scsi generic sg3 type 0
> [   18.540362] sata-dwc 4bffd1000.sata: sata_dwc_qc_prep_by_tag: port=0 dma dir=from device n_elem=1
> [   18.540370] dma dma0chan0: dwc_prep_slave_sg
> [   18.540378] dma dma0chan0: scanned 1 descriptors on freelist
> [   18.540387] sata-dwc 4bffd1000.sata: dma_dwc_xfer_setup sg: 0xed37f200, count: 1 addr: 0xfffffffff6a18400
> [   18.540395] sata-dwc 4bffd1000.sata: sata_dwc_qc_issue: tag=0 ap->link.sactive = 0x00000001 sactive=0x00000001
> [   18.540426] sata-dwc 4bffd1000.sata: sata_dwc_exec_command_by_tag cmd(0x60): READ FPDMA QUEUED tag=0
> [   18.556592] sata-dwc 4bffd1000.sata: sata_dwc_isr intpr=0x00000082 active_tag=-84148995
> [   18.556599] sata-dwc 4bffd1000.sata: sata_dwc_isr: NEWFP tag=0
> [   18.556609] sata-dwc 4bffd1000.sata: sata_dwc_bmdma_start_by_tag qc=ed2180b8 tag: 0 cmd: 0x60 dma_dir: from device start_dma? 1
> [   18.556616] sata-dwc 4bffd1000.sata: taskfile cmd: 0x60 protocol: ATA NCQ flags: 0x17 device: 40
> [   18.556623] sata-dwc 4bffd1000.sata: feature: 0x08 nsect: 0x0 lbal: 0x0 lbam: 0x0 lbah: 0x0
> [   18.556631] sata-dwc 4bffd1000.sata: hob_feature: 0x00 hob_nsect: 0x0 hob_lbal: 0x0 hob_lbam: 0x0 hob_lbah: 0x0
> [   18.556639] dma dma0chan0: dwc_tx_submit: queued 2
> [   18.556646] dma dma0chan0: dwc_dostart_first_queued: started 2
> [   48.748634] ata3: lost interrupt (Status 0x40)
> [   48.753465] sata-dwc 4bffd1000.sata: sata_dwc_scr_read: id=3 reg=1 val=val=0x00000000
> [   48.761369] ata3.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x6 frozen
> [   48.769671] ata3.00: failed command: READ FPDMA QUEUED

Well, that didn't help.  I still think it's part of the problem, but
something else must be wrong as well.  The various Master Select fields
look like a good place to start.  Also, the manual says the LLP_SRC_EN
and LLP_DST_EN flags should be cleared on the last in a chain of blocks.
The old sata_dwc driver does this whereas dw_dma does not.

It might be worthwhile to try reverting drivers/ata/sata_dwc_460ex.c to
v4.0 (leaving the rest at 4.4-rc5) just to make sure that's a good
reference.  I've verified that this builds.

-- 
Måns Rullgård
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