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Date: Sat, 19 Dec 2015 15:40:30 +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 12/18/2015 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.
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 <mans@...sr.com>
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 <mans@...sr.com>
---
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
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