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Date:   Mon, 15 Mar 2021 15:52:38 +0100
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     Amey Narkhede <ameynarkhede03@gmail.com>, bhelgaas@google.com,
        raphael.norwitz@nutanix.com, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org
Subject: Re: [PATCH 4/4] PCI/sysfs: Allow userspace to query and set device
 reset mechanism
Message-ID: <20210315145238.6sg5deblr2z2pupu@pali>
References: <20210312173452.3855-1-ameynarkhede03@gmail.com>
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 <20210314235545.girtrazsdxtrqo2q@pali>
 <20210315134323.llz2o7yhezwgealp@archlinux>
 <20210315135226.avwmnhkfsgof6ihw@pali>
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On Monday 15 March 2021 08:34:09 Alex Williamson wrote:
> On Mon, 15 Mar 2021 14:52:26 +0100
> Pali Rohár <pali@kernel.org> wrote:
> 
> > On Monday 15 March 2021 19:13:23 Amey Narkhede wrote:
> > > slot reset (pci_dev_reset_slot_function) and secondary bus
> > > reset(pci_parent_bus_reset) which I think are hot reset and
> > > warm reset respectively.  
> > 
> > No. PCI secondary bus reset = PCIe Hot Reset. Slot reset is just another
> > type of reset, which is currently implemented only for PCIe hot plug
> > bridges and for PowerPC PowerNV platform and it just call PCI secondary
> > bus reset with some other hook. PCIe Warm Reset does not have API in
> > kernel and therefore drivers do not export this type of reset via any
> > kernel function (yet).
> 
> Warm reset is beyond the scope of this series, but could be implemented
> in a compatible way to fit within the pci_reset_fn_methods[] array
> defined here.

Ok!

> Note that with this series the resets available through
> pci_reset_function() and the per device reset attribute is sysfs remain
> exactly the same as they are currently.  The bus and slot reset
> methods used here are limited to devices where only a single function is
> affected by the reset, therefore it is not like the patch you proposed
> which performed a reset irrespective of the downstream devices.  This
> series only enables selection of the existing methods.  Thanks,
> 
> Alex
> 

But with this patch series, there is still an issue with PCI secondary
bus reset mechanism as exported sysfs attribute does not do that
remove-reset-rescan procedure. As discussed in other thread, this reset
let device in unconfigured / broken state.