linux-kernel - Re: [PATCH v2 2/2] PCI: Reduce warnings on possible RW1C corruption

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Date:   Mon, 3 Aug 2020 03:42:44 +0000
From:   Mark Tomlinson <Mark.Tomlinson@...iedtelesis.co.nz>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "ray.jui@...adcom.com" <ray.jui@...adcom.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "sbranden@...adcom.com" <sbranden@...adcom.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>
Subject: Re: [PATCH v2 2/2] PCI: Reduce warnings on possible RW1C corruption

On Fri, 2020-07-31 at 09:32 -0600, Rob Herring wrote:
> 
> If we don't want to just warn when a 8 or 16 bit access occurs (I'm
> not sure if 32-bit only accesses is possible or common. Seems like
> PCI_COMMAND would always get written?), then a simple way to do this
> is just move this out of line and do something like this where the bus
> or device is created/registered:
> 
> if (bus->ops->write == pci_generic_config_write32)
>     warn()
> 
This doesn't work for many of the PCI drivers, since they wrap the call
to pci_generic_config_write32() in their own function.

> > 
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 34c1c4f45288..5b6ab593ae09 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -613,6 +613,7 @@ struct pci_bus {
> >         unsigned char   primary;        /* Number of primary bridge */
> >         unsigned char   max_bus_speed;  /* enum pci_bus_speed */
> >         unsigned char   cur_bus_speed;  /* enum pci_bus_speed */
> > +       bool            unsafe_warn;    /* warned about RW1C config write */
> 
> Make this a bitfield next to 'is_added'.

Will do, thanks.