Re: [PATCH 2/2] PCI/DPC: Use defines with register fields

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Oct 13, 2023 at 02:20:04PM +0300, Ilpo Järvinen wrote:
> Use defines instead of literals and replace custom masking and shifts
> with FIELD_GET() where it makes sense.
> ...

>  	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CAP, &cap);
> -	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl);
>  
> -	ctl = (ctl & 0xfff4) | PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN;
> +	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl);
> +	ctl |= PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN;
> +	ctl &= ~PCI_EXP_DPC_CTL_EN_NONFATAL;

This has been a little obtuse from the beginning.

The original clears bits 0, 1, 3, then sets bits 0 and 3.
The new code sets bits 0, 3, then clears bit 1.

These are equivalent, but it's definitely some work to verify it.

I think the point is to enable DPC on ERR_FATAL (but not ERR_NONFATAL)
and to enable DPC interrupts.  What about something like this?

  #define PCI_EXP_DPC_CTL_EN_MASK  0x0003

  ctl &= ~PCI_EXP_DPC_CTL_EN_MASK;
  ctl |= PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN;

>  	pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl);
> -	pci_info(pdev, "enabled with IRQ %d\n", dev->irq);
>  
> +	pci_info(pdev, "enabled with IRQ %d\n", dev->irq);
>  	pci_info(pdev, "error containment capabilities: Int Msg #%d, RPExt%c PoisonedTLP%c SwTrigger%c RP PIO Log %d, DL_ActiveErr%c\n",
>  		 cap & PCI_EXP_DPC_IRQ, FLAG(cap, PCI_EXP_DPC_CAP_RP_EXT),
>  		 FLAG(cap, PCI_EXP_DPC_CAP_POISONED_TLP),
> -- 
> 2.30.2
>