lkml.org 
[lkml]   [2022]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] PCI: tegra: Use PCI_CONF1_EXT_ADDRESS() macro
From

On 11/10/2022 17:16, Pali Rohár wrote:

...

> I see, this is stupid mistake. PCIe config read and write operations
> needs to be 4-byte aligned, so normally it is done by calculating 4-byte
> aligned base address and then using appropriate cpu load/store
> instruction to access just defined size/offset of 4-byte config space
> register.
>
> pci-tegra.c is using common helper functions pci_generic_config_read()
> and pci_generic_config_write(), which expects final address with offset,
> and not 4-byte aligned address.
>
> I'm not sure what should be the proper fix, but for me it looks like
> that pci_generic_config_read() and pci_generic_config_write() could be
> adjusted to handle it.
>
> In any case, above patch is a regressions and I see there two options
> for now:
>
> 1) Reverting that patch
>
> 2) Adding "offset |= where & 0x3;" after the PCI_CONF1_EXT_ADDRESS()
> macro to set also lower 2 bits of accessed register.
>
> Jon, Lorenzo, what do you think? Could you test if 2) is working fine?


I tested 'offset |= where & 0xff' which is essentially the same as the
above and that is working and so I am sure that the above works too.
However, I do wonder if reverting is simpler because we already have a
'& ~PCI_CONF1_ENABLE' and now adding '| where & 0x3' seems to diminish
the value of this change.

Cheers
Jon

--
nvpublic

\
 
 \ /
  Last update: 2022-10-11 18:48    [W:0.061 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site