Julian Margetson [off-list ref] writes:

On 12/18/2015 10:34 PM, Andy Shevchenko wrote:

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On Sat, Dec 19, 2015 at 1:16 AM, Måns Rullgård [off-list ref] wrote:

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Julian Margetson [off-list ref] writes:

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On 12/18/2015 6:33 PM, Måns Rullgård wrote:

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Julian Margetson [off-list ref] writes:

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On 12/18/2015 1:18 PM, Måns Rullgård wrote:

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Julian Margetson [off-list ref] writes:

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On 12/18/2015 8:49 AM, Måns Rullgård wrote:

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Andy Shevchenko [off-list ref] writes:

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[    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@julian-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.

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[...]

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[   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.

OK, I've found something.  The dma setup errors are benign, caused by
the driver calling dmaengine_prep_slave_sg() even for non-dma
operations.  The real error is the lock recursion that's reported
later.  I wasn't seeing it since I was running a UP non-preempt kernel.
With lock debugging enabled, I get the same error.  This patch should
fix it.

---8<---
From 94c4769d2171ce66079fd486a45e09dd64db62c0 Mon Sep 17 00:00:00 2001
From: Mans Rullgard <redacted>
Date: Sat, 19 Dec 2015 15:26:23 +0000
Subject: [PATCH] ata: sata_dwc_460ex: remove incorrect locking

This lock is already taken in ata_scsi_queuecmd() a few levels up the
call stack so attempting to take it here is an error.  Moreover, it is
pointless in the first place since it only protects a single, atomic
assignment.

Signed-off-by: Mans Rullgard <redacted>
---
 drivers/ata/sata_dwc_460ex.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 799df86..5696f39 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c

@@ -1001,16 +1001,14 @@ static void sata_dwc_exec_command_by_tag(struct ata_port *ap,
 					 struct ata_taskfile *tf,
 					 u8 tag, u32 cmd_issued)
 {
-	unsigned long flags;
 	struct sata_dwc_device_port *hsdevp = HSDEVP_FROM_AP(ap);
 	struct sata_dwc_device *hsdev = HSDEV_FROM_AP(ap);
 
 	dev_dbg(ap->dev, "%s cmd(0x%02x): %s tag=%d\n", __func__, tf->command,
 		ata_get_cmd_descript(tf->command), tag);
 
-	spin_lock_irqsave(&ap->host->lock, flags);
 	hsdevp->cmd_issued[tag] = cmd_issued;
-	spin_unlock_irqrestore(&ap->host->lock, flags);
+
 	/*
 	 * Clear SError before executing a new command.
 	 * sata_dwc_scr_write and read can not be used here. Clearing the PM

-- 
2.6.3

-- 
Måns Rullgård