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From: Shanker R Donthineni <sdonthineni@nvidia.com>
To: Bjorn Helgaas <helgaas@kernel.org>,
	Amey Narkhede <ameynarkhede03@gmail.com>
Cc: <alex.williamson@redhat.com>,
	Raphael Norwitz <raphael.norwitz@nutanix.com>,
	<linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<kw@linux.com>, Sinan Kaya <okaya@kernel.org>,
	Len Brown <lenb@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v10 2/8] PCI: Add new array for keeping track of ordering of reset methods
Date: Wed, 28 Jul 2021 13:17:26 -0500	[thread overview]
Message-ID: <afaf66ea-2eee-cd16-ede8-095b8b6a6de6@nvidia.com> (raw)
In-Reply-To: <20210728175911.GA835695@bjorn-Precision-5520>

Hi Bjorn,

On 7/28/21 12:59 PM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
>
>
> On Wed, Jul 28, 2021 at 11:15:19PM +0530, Amey Narkhede wrote:
>> On 21/07/27 05:59PM, Bjorn Helgaas wrote:
>>> On Fri, Jul 09, 2021 at 06:08:07PM +0530, Amey Narkhede wrote:
>>>> Introduce a new array reset_methods in struct pci_dev to keep track of
>>>> reset mechanisms supported by the device and their ordering.
>>>>
>>>> Also refactor probing and reset functions to take advantage of calling
>>>> convention of reset functions.
>>>>
>>>> Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
>>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>>>> Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
>>>> ---
>>>>  drivers/pci/pci.c   | 92 ++++++++++++++++++++++++++-------------------
>>>>  drivers/pci/pci.h   |  9 ++++-
>>>>  drivers/pci/probe.c |  5 +--
>>>>  include/linux/pci.h |  7 ++++
>>>>  4 files changed, 70 insertions(+), 43 deletions(-)
>>>>
>> [...]
>>>> + BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);
>>>>
>>>>   might_sleep();
>>>>
>>>> - rc = pci_dev_specific_reset(dev, 1);
>>>> - if (rc != -ENOTTY)
>>>> -         return rc;
>>>> - rc = pcie_reset_flr(dev, 1);
>>>> - if (rc != -ENOTTY)
>>>> -         return rc;
>>>> - rc = pci_af_flr(dev, 1);
>>>> - if (rc != -ENOTTY)
>>>> -         return rc;
>>>> - rc = pci_pm_reset(dev, 1);
>>>> - if (rc != -ENOTTY)
>>>> -         return rc;
>>>> + for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
>>>> +         rc = pci_reset_fn_methods[i].reset_fn(dev, 1);
>>>> +         if (!rc)
>>>> +                 reset_methods[n++] = i;
>>> Why do we need this local reset_methods[] array?  Can we just fill
>>> in dev->reset_methods[] directly and skip the memcpy() below?
>>>
>> This is for avoiding caching of previously supported reset methods.
>> Is it okay if I use memset(dev->reset_methods, 0,
>> sizeof(dev->reset_methods)) instead to clear the values in
>> dev->reset_methods?
> I don't think there's ever a case where you look at a
> dev->reset_methods[] element past a zero value, so we shouldn't care
> about any previously-supported methods left in the array.
>
> If we *do* look at something past a zero value, why do we do that?  It
> sounds like it would be a bug.
>

I think either we need memset or clear 0th/last element. Can we set the last
index explicitly to zero?

void pci_init_reset_methods(struct pci_dev *dev)
{
        int i, n, rc;

        BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);

        might_sleep();

        n = 0;
        for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
                rc = pci_reset_fn_methods[i].reset_fn(dev, 1);
                if (!rc)
                        dev->reset_methods[n++] = i;
                else if (rc != -ENOTTY)
                        break;
        }
        dev->reset_methods[n] = 0;
}






  reply	other threads:[~2021-07-28 18:17 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09 12:38 [PATCH v10 0/8] Expose and manage PCI device reset Amey Narkhede
2021-07-09 12:38 ` [PATCH v10 1/8] PCI: Add pcie_reset_flr to follow calling convention of other reset methods Amey Narkhede
2021-07-12 22:07   ` Alex Williamson
2021-07-27 22:12   ` Bjorn Helgaas
2021-07-28 18:54     ` Shanker R Donthineni
2021-07-28 20:23       ` Bjorn Helgaas
2021-07-28 21:58         ` Shanker R Donthineni
2021-07-28 22:04           ` Shanker R Donthineni
2021-07-28 22:16           ` Bjorn Helgaas
2021-07-09 12:38 ` [PATCH v10 2/8] PCI: Add new array for keeping track of ordering of " Amey Narkhede
2021-07-27 22:59   ` Bjorn Helgaas
2021-07-28 17:45     ` Amey Narkhede
2021-07-28 17:59       ` Bjorn Helgaas
2021-07-28 18:17         ` Shanker R Donthineni [this message]
2021-07-28 18:08       ` Shanker R Donthineni
2021-07-28 18:31     ` Shanker R Donthineni
2021-07-28 20:25       ` Bjorn Helgaas
2021-07-28 22:01         ` Shanker R Donthineni
2021-07-09 12:38 ` [PATCH v10 3/8] PCI: Remove reset_fn field from pci_dev Amey Narkhede
2021-07-09 12:38 ` [PATCH v10 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism Amey Narkhede
2021-07-27 23:28   ` Bjorn Helgaas
2021-07-28  1:27     ` Krzysztof Wilczyński
2021-07-28 15:36       ` Bjorn Helgaas
2021-07-28 17:59     ` Amey Narkhede
2021-07-28 18:13       ` Bjorn Helgaas
2021-07-28 18:58         ` Amey Narkhede
2021-07-28 20:18           ` Bjorn Helgaas
2021-07-31 19:15     ` Amey Narkhede
2021-07-28 17:09   ` Bjorn Helgaas
2021-07-09 12:38 ` [PATCH v10 5/8] PCI: Define a function to set ACPI_COMPANION in pci_dev Amey Narkhede
2021-07-12 22:29   ` Alex Williamson
2021-07-09 12:38 ` [PATCH v10 6/8] PCI: Setup ACPI fwnode early and at the same time with OF Amey Narkhede
2021-07-12 23:09   ` Alex Williamson
2021-07-27 23:30   ` Bjorn Helgaas
2021-07-27 23:50     ` Shanker R Donthineni
2021-07-09 12:38 ` [PATCH v10 7/8] PCI: Add support for ACPI _RST reset method Amey Narkhede
2021-07-12 23:09   ` Alex Williamson
2021-07-13  0:51     ` Shanker R Donthineni
2021-07-14 22:56       ` Alex Williamson
2021-07-09 12:38 ` [PATCH v10 8/8] PCI: Change the type of probe argument in reset functions Amey Narkhede
2021-07-12 22:24   ` Alex Williamson
2021-07-27 22:22   ` Bjorn Helgaas
2021-07-28 17:35     ` Amey Narkhede
2021-07-28 17:55       ` Bjorn Helgaas
2021-07-09 12:46 ` [PATCH v10 0/8] Expose and manage PCI device reset Amey Narkhede

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