Re: [PATCH v2] idpf: disable PCIe PTM on probe failure and removal

[Tony Nguyen]

On 7/15/2026 12:43 AM, Myeonghun Pak wrote:
> idpf_probe() enables PCIe Precision Time Measurement with
> pci_enable_ptm(pdev, NULL), which programs the PTM control bits and sets
> pdev->ptm_enabled when the bus/controller supports it.
>
> If a later probe step fails, the error path releases the allocated
> workqueues and adapter memory without disabling PTM.  The remove path has
> the same imbalance when a successfully probed device is detached.  In
> both cases, the PCI core's software PTM state and the device's PTM control
> bits remain set with no bound driver.
>
> Add pci_disable_ptm() to the common probe unwind after the PTM enable and
> to idpf_remove().  pci_disable_ptm() is a no-op when PTM was not enabled,
> so the non-fatal pci_enable_ptm() failure remains safe.
> pcim_enable_device() only arranges for pci_disable_device() and does not
> undo the PTM enable.
>
> Fixes: 8d5e12c5921c ("idpf: add initial PTP support")
> Co-developed-by: Ijae Kim <ae878000@xxxxxxxxx>
> Signed-off-by: Ijae Kim <ae878000@xxxxxxxxx>
> Signed-off-by: Myeonghun Pak <mhun512@xxxxxxxxx>
> ---
> Changes in v2:
> - Disable PTM in the probe error path, as requested by Emil Tantilov.
>
>   drivers/net/ethernet/intel/idpf/idpf_main.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_main.c b/drivers/net/ethernet/intel/idpf/idpf_main.c
> index 0dd741dcfc..f08ce13c20 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_main.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_main.c
> @@ -159,6 +159,7 @@ static void idpf_remove(struct pci_dev *pdev)
>   	mutex_destroy(&adapter->queue_lock);
>   	mutex_destroy(&adapter->vc_buf_lock);
>   
> +	pci_disable_ptm(pdev);

Sashiko says:

If pci_enable_ptm() failed earlier during idpf_probe() because it was
unsupported by the bus or controller, does this unconditional call to
pci_disable_ptm() corrupt the upstream PTM enable counts?
Looking at pci_disable_ptm(), it does not check if the local device was
successfully enabled. It climbs the PCIe tree and erroneously decrements
atomic counters like ptm_enable_cnt on parent switches.
Could this eventually break PTM for other downstream devices sharing the 
same
switch if a parent's count is incorrectly decremented to -1?

>   	pci_set_drvdata(pdev, NULL);
>   	kfree(adapter);
>   }
> @@ -266,7 +267,7 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	if (err) {
>   		pci_err(pdev, "DMA configuration failed: %pe\n", ERR_PTR(err));
>   
> -		goto err_free;
> +		goto err_disable_ptm;
>   	}
>   
>   	pci_set_master(pdev);
> @@ -279,7 +280,7 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	if (!adapter->init_wq) {
>   		dev_err(dev, "Failed to allocate init workqueue\n");
>   		err = -ENOMEM;
> -		goto err_free;
> +		goto err_disable_ptm;
>   	}
>   
>   	adapter->serv_wq = alloc_workqueue("%s-%s-service",
> @@ -366,6 +367,8 @@ err_mbx_wq_alloc:
>   	destroy_workqueue(adapter->serv_wq);
>   err_serv_wq_alloc:
>   	destroy_workqueue(adapter->init_wq);
> +err_disable_ptm:
> +	pci_disable_ptm(pdev);

Like the issue in idpf_remove(), does this error path unconditionally 
disable
PTM even if the earlier enable attempt failed?
If a subsequent probe step fails (such as dma_set_mask_and_coherent or
workqueue allocation), this path is taken regardless of whether
pci_enable_ptm() succeeded.
Would it make sense to track the PTM state in the adapter struct, and only
call pci_disable_ptm() when it was successfully enabled?

>   err_free:
>   	kfree(adapter);
>   	return err;