Re: [PATCH v1 1/1] spi: Remove unneded check for orig_nents

[Neil Armstrong <neil.armstrong@linaro.org>]

On 22/05/2024 13:33, Andy Shevchenko wrote:
> On Wed, May 22, 2024 at 12:03:33PM +0200, Neil Armstrong wrote:
>> On 15/05/2024 23:09, Nícolas F. R. A. Prado wrote:
>>> On Tue, May 07, 2024 at 11:10:27PM +0300, Andy Shevchenko wrote:
>>>> Both dma_unmap_sgtable() and sg_free_table() in spi_unmap_buf_attrs()
>>>> have checks for orig_nents against 0. No need to duplicate this.
>>>> All the same applies to other DMA mapping API calls.
>>>>
>>>> Also note, there is no other user in the kernel that does this kind of
>>>> checks.
>>>>
>>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>>
>>> Hi,
>>>
>>> this commit caused a regression which I reported here:
>>>
>>> https://lore.kernel.org/all/d3679496-2e4e-4a7c-97ed-f193bd53af1d@notapiano
>>>
>>> along with some thoughts on the cause and a possible solution, though I'm not
>>> familiar with this code base at all and would really appreciate any feedback you
>>> may have.
>>
>> I also see the same regression on the SM8550 and SM8650 platforms,
>> please CC linux-arm-msm@vger.kernel.org and me for a potential fix to test on those platforms.
> 
> There is still no answer from IOMMU patch author. Do you have the same trace
> due to IOMMU calls? Anyway, I guess it would be nice to see it.

Yes :
[    6.404623] Unable to handle kernel NULL pointer dereference at virtual address 000000000000001c
<snip>
[    6.641597] lr : __dma_sync_sg_for_device+0x3c/0x40
<snip>
[    6.688286] Call trace:
[    6.688287]  iommu_dma_sync_sg_for_device+0x28/0x100
[    6.717582]  __dma_sync_sg_for_device+0x3c/0x40
[    6.717585]  spi_transfer_one_message+0x358/0x680
[    6.732229]  __spi_pump_transfer_message+0x188/0x494
[    6.732232]  __spi_sync+0x2a8/0x3c4
[    6.732234]  spi_sync+0x30/0x54
[    6.732236]  goodix_berlin_spi_write+0xf8/0x164 [goodix_berlin_spi]
[    6.739854]  _regmap_raw_write_impl+0x538/0x674
[    6.750053]  _regmap_raw_write+0xb4/0x144
[    6.750056]  regmap_raw_write+0x7c/0xc0
[    6.750058]  goodix_berlin_power_on+0xb0/0x1b0 [goodix_berlin_core]
[    6.765520]  goodix_berlin_probe+0xc0/0x660 [goodix_berlin_core]
[    6.765522]  goodix_berlin_spi_probe+0x12c/0x14c [goodix_berlin_spi]
[    6.772339]  spi_probe+0x84/0xe4
[    6.772342]  really_probe+0xbc/0x29c
[    6.784313]  __driver_probe_device+0x78/0x12c
[    6.784316]  driver_probe_device+0x3c/0x15c
[    6.784319]  __driver_attach+0x90/0x19c
[    6.784322]  bus_for_each_dev+0x7c/0xdc
[    6.794520]  driver_attach+0x24/0x30
[    6.794523]  bus_add_driver+0xe4/0x208
[    6.794526]  driver_register+0x5c/0x124
[    6.802586]  __spi_register_driver+0xa4/0xe4
[    6.802589]  goodix_berlin_spi_driver_init+0x20/0x1000 [goodix_berlin_spi]
[    6.802591]  do_one_initcall+0x80/0x1c8
[    6.902310]  do_init_module+0x60/0x218
[    6.921988]  load_module+0x1bcc/0x1d8c
[    6.925847]  init_module_from_file+0x88/0xcc
[    6.930238]  __arm64_sys_finit_module+0x1dc/0x2e4
[    6.935074]  invoke_syscall+0x48/0x114
[    6.938944]  el0_svc_common.constprop.0+0xc0/0xe0
[    6.943781]  do_el0_svc+0x1c/0x28
[    6.947195]  el0_svc+0x34/0xd8
[    6.950348]  el0t_64_sync_handler+0x120/0x12c
[    6.954833]  el0t_64_sync+0x190/0x194
[    6.958600] Code: 2a0203f5 2a0303f6 a90363f7 aa0003f7 (b9401c2

Reverting  8cc3bad9d9d6 ("spi: Remove unneded check for orig_nents") removes the crash.

> 
> Meanwhile, I have three changes I posted in the replies to the initial report,
> can you combine them all and test? This will be a plan B (? or A, depending on
> the culprit).
> 

I'll try to apply them and test.

Neil