linux-kernel - Re: [PATCH v2 1/2] platform/x86: amd-pmc: Store the pci_dev instance inside struct amd_pmc

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Date:   Fri, 22 Oct 2021 10:51:01 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Goswami, Sanket" <Sanket.Goswami@....com>,
        Shyam-sundar.S-k@....com, mgross@...ux.intel.com
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] platform/x86: amd-pmc: Store the pci_dev instance
 inside struct amd_pmc_dev

Hi Sanket,

On 10/22/21 08:55, Goswami, Sanket wrote:
> Hi Hans,
> 
> On 21-Oct-21 23:48, Hans de Goede wrote:
>> [CAUTION: External Email]
>>
>> Hi,
>>
>> On 10/21/21 11:29, Sanket Goswami wrote:
>>> Store the root port information in amd_pmc_probe() so that the
>>> information can be used across multiple routines.
>>>
>>> Signed-off-by: Sanket Goswami <Sanket.Goswami@....com>
>>> ---
>>> Changes in v2:
>>> - Store the rdev info in amd_pmc_probe() as suggested by Hans.
>>
>> Thank you, but there are still some issues, see below.
>>
>>
>>>  drivers/platform/x86/amd-pmc.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/platform/x86/amd-pmc.c b/drivers/platform/x86/amd-pmc.c
>>> index 55f14bdfdbfd..502f37eaba1f 100644
>>> --- a/drivers/platform/x86/amd-pmc.c
>>> +++ b/drivers/platform/x86/amd-pmc.c
>>> @@ -119,6 +119,7 @@ struct amd_pmc_dev {
>>>       u16 minor;
>>>       u16 rev;
>>>       struct device *dev;
>>> +     struct pci_dev *rdev;
>>>       struct mutex lock; /* generic mutex lock */
>>>  #if IS_ENABLED(CONFIG_DEBUG_FS)
>>>       struct dentry *dbgfs_dir;
>>> @@ -482,6 +483,7 @@ static int amd_pmc_probe(struct platform_device *pdev)
>>>               return -ENODEV;
>>>       }
>>>
>>> +     dev->rdev = rdev;
>>>       dev->cpu_id = rdev->device;
>>>       err = pci_write_config_dword(rdev, AMD_PMC_SMU_INDEX_ADDRESS, AMD_PMC_BASE_ADDR_LO);
>>>       if (err) {
>>> @@ -512,7 +514,6 @@ static int amd_pmc_probe(struct platform_device *pdev)
>>>       }
>>>
>>>       base_addr_hi = val & AMD_PMC_BASE_ADDR_LO_MASK;
>>> -     pci_dev_put(dev->rdev);
>>
>> The current code here actually reads:
>>
>>         pci_dev_put(rdev);
>>
>> Note (rdev) not (dev->rdev). I don't know what you based this on, this is weird.
> 
> rdev is already retrieved before doing this:
> 	     pci_dev_put(dev->rdev);
> 
> i.e.
> in amd_pmc_probe()
> 
> rdev = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0, 0));
> 	if (!rdev || !pci_match_id(pmc_pci_ids, rdev)) {
> 		pci_dev_put(rdev);
> 		return -ENODEV;
> 	}
> 
> after this I am storing rdev in "dev->rdev"
> i.e.
> dev->rdev = rdev;
> 
> after this I am using "dev->rdev" at places where "rdev" was getting used earlier.
> Do you see any problem?

What I was trying to say is that the patch does not apply, because it is
trying to remove the pci_put_dev() line from a block of code like this:

	base_addr_hi = val & AMD_PMC_BASE_ADDR_LO_MASK;
	pci_dev_put(dev->rdev);
	base_addr = ((u64)base_addr_hi << 32 | base_addr_lo);

But the actual code in platform-drivers-x86/review-hans (and for-next too) has:

	base_addr_hi = val & AMD_PMC_BASE_ADDR_LO_MASK;
	pci_dev_put(rdev);
	base_addr = ((u64)base_addr_hi << 32 | base_addr_lo);



After your patch using dev->rdev instead of just rdev is fine
(but please be consistent, which would mean use just rdev everywhere).

But your patch is removing a line which does not exist in that form,
IOW it is based on some intermediate version of amd-pmc.c and not
on the HEAD of platform-drivers-x86/review-hans.

Regards,

Hans






> 
>>
>> Also there are a bunch of error-exits from amd_pmc_probe() which not all
>> need a "pci_dev_put(rdev)" added to them before there "return ERROR;"
>> statement.
>>
>> It would be best to add:
>>
>> err_pci_dev_put:
>>         pci_dev_put(rdev);
>>         return err;
>>
>> Add the end off the function (after the return 0;) and replace all
>> "return FOO" error-exits with:
>>
>>                 err = <FOO>;
>>                 goto err_pci_dev_put;
>>         }
>>
> Thank you, will take it as a separate patch in v3.
> 
> 
> Thanks,
> Sanket
>