From: Bjorn Helgaas <helgaas@kernel.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Heiner Kallweit <hkallweit1@gmail.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Jonathan Corbet <corbet@lwn.net>, Jens Axboe <axboe@kernel.dk>,
Viresh Kumar <vireshk@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Vinod Koul <vkoul@kernel.org>, David Miller <davem@davemloft.net>,
Lee Jones <lee.jones@linaro.org>,
Ion Badulescu <ionut@badula.org>,
Jakub Kicinski <kuba@kernel.org>,
Lino Sanfilippo <LinoSanfilippo@gmx.de>,
Christian Lamparter <chunkeey@googlemail.com>,
Kalle Valo <kvalo@codeaurora.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Adam Radford <aradford@gmail.com>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Smart <james.smart@broadcom.com>,
Dick Kennedy <dick.kennedy@broadcom.com>,
Nilesh Javali <njavali@marvell.com>,
GR-QLogic-Storage-Upstream@marvell.com,
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"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
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Subject: Re: [PATCH] PCI: Remove pci_try_set_mwi
Date: Fri, 26 Mar 2021 16:55:16 -0500 [thread overview]
Message-ID: <20210326215516.GA916324@bjorn-Precision-5520> (raw)
In-Reply-To: <YF5VVjQ7q/JBSR1Z@smile.fi.intel.com>
On Fri, Mar 26, 2021 at 11:42:46PM +0200, Andy Shevchenko wrote:
> On Fri, Mar 26, 2021 at 04:26:55PM -0500, Bjorn Helgaas wrote:
> > [+cc Randy, Andrew (though I'm sure you have zero interest in this
> > ancient question :))]
> >
> > On Wed, Dec 09, 2020 at 09:31:21AM +0100, Heiner Kallweit wrote:
> > > pci_set_mwi() and pci_try_set_mwi() do exactly the same, just that the
> > > former one is declared as __must_check. However also some callers of
> > > pci_set_mwi() have a comment that it's an optional feature. I don't
> > > think there's much sense in this separation and the use of
> > > __must_check. Therefore remove pci_try_set_mwi() and remove the
> > > __must_check attribute from pci_set_mwi().
> > > I don't expect either function to be used in new code anyway.
> >
> > There's not much I like better than removing things. But some
> > significant thought went into adding pci_try_set_mwi() in the first
> > place, so I need a little more convincing about why it's safe to
> > remove it.
> >
> > The argument should cite the discussion about adding it. I think one
> > of the earliest conversations is here:
> > https://lore.kernel.org/linux-ide/20070404213704.224128ec.randy.dunlap@oracle.com/
>
> It's solely PCI feature which is absent on PCIe.
>
> So, if there is a guarantee that the driver never services a device connected
> to old PCI bus, it's okay to remove the call (it's no-op on PCIe anyway).
Yes, I'm aware that MWI is a no-op on PCIe. If we want to argue that
we don't need to support Conventional PCI devices, that should be
explicit, and we could remove pci_set_mwi() completely. But I don't
think we're ready to drop Conventional PCI support.
> OTOH, PCI core may try MWI itself for every device (but this is an opposite,
> what should we do on broken devices that do change their state based on that
> bit while violating specification).
>
> In any case
>
> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Thanks!
Bjorn
next prev parent reply other threads:[~2021-03-26 21:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 8:31 [PATCH] PCI: Remove pci_try_set_mwi Heiner Kallweit
2020-12-09 8:40 ` Kalle Valo
2020-12-09 9:03 ` Vinod Koul
2020-12-09 9:20 ` Peter Chen
2020-12-09 9:22 ` Lee Jones
2020-12-09 10:59 ` Andy Shevchenko
2020-12-09 11:02 ` Andy Shevchenko
2021-03-26 21:26 ` Bjorn Helgaas
2021-03-26 21:42 ` Andy Shevchenko
2021-03-26 21:55 ` Bjorn Helgaas [this message]
2021-03-27 23:04 ` Heiner Kallweit
2021-03-28 19:58 ` Bjorn Helgaas
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