linux-kernel - Re: [PATCH 2/6] device/pci: add cmdmem cap to pci

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Message-ID: <2fb7ca3e-504a-19d7-2e7b-b34ecc481ffc@intel.com>
Date:   Tue, 31 Mar 2020 10:38:31 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     vkoul@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, bhelgaas@...gle.com, arnd@...db.de,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        dmaengine@...r.kernel.org, dan.j.williams@...el.com,
        ashok.raj@...el.com, fenghua.yu@...el.com,
        linux-pci@...r.kernel.org, tony.luck@...el.com, jing.lin@...el.com,
        sanjay.k.kumar@...el.com
Subject: Re: [PATCH 2/6] device/pci: add cmdmem cap to pci_dev


On 3/31/2020 10:24 AM, Greg KH wrote:
> On Tue, Mar 31, 2020 at 10:07:07AM -0700, Dave Jiang wrote:
>> On 3/31/2020 3:04 AM, Greg KH wrote:
>>> On Mon, Mar 30, 2020 at 02:27:00PM -0700, Dave Jiang wrote:
>>>> Since the current accelerator devices do not have standard PCIe capability
>>>> enumeration for accepting ENQCMDS yet, for now an attribute of pdev->cmdmem has
>>>> been added to struct pci_dev.  Currently a PCI quirk must be used for the
>>>> devices that have such cap until the PCI cap is standardized. Add a helper
>>>> function to provide the check if a device supports the cmdmem capability.
>>>>
>>>> Such capability is expected to be added to PCIe device cap enumeration in
>>>> the future.
>>>>
>>>> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
>>>> ---
>>>>    drivers/base/core.c    |   13 +++++++++++++
>>>>    include/linux/device.h |    2 ++
>>>>    include/linux/pci.h    |    1 +
>>>>    3 files changed, 16 insertions(+)
>>>>
>>>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>>>> index dbb0f9130f42..cd9f5b040ed4 100644
>>>> --- a/drivers/base/core.c
>>>> +++ b/drivers/base/core.c
>>>> @@ -27,6 +27,7 @@
>>>>    #include <linux/netdevice.h>
>>>>    #include <linux/sched/signal.h>
>>>>    #include <linux/sysfs.h>
>>>> +#include <linux/pci.h>
>>>>    #include "base.h"
>>>>    #include "power/power.h"
>>>> @@ -3790,3 +3791,15 @@ int device_match_any(struct device *dev, const void *unused)
>>>>    	return 1;
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(device_match_any);
>>>> +
>>>> +bool device_supports_cmdmem(struct device *dev)
>>>> +{
>>>> +	struct pci_dev *pdev;
>>>> +
>>>> +	if (!dev_is_pci(dev))
>>>> +		return false;
>>>> +
>>>> +	pdev = to_pci_dev(dev);
>>>> +	return pdev->cmdmem;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(device_supports_cmdmem);
>>> Why would a pci-specific function like this be ok to have in the driver
>>> core?  Please keep it in the pci core code instead.
>> The original thought was to introduce a new arch level memory mapping
>> semantic.
> Please do not.  Also, that's not what you are doing here from what I can
> tell.
>
>> If you feel this should be PCI exclusive, should we make the ioremap
>> routines for this memory type pci specific as well?
> Why wouldn't it be?  Is this needed anywhere else?

Ok I'll make this pci specific.


>
> thanks,
>
> greg k-h