Re: [PATCH v7 3/5] Add debugfs based silicon debug support in DWC

[Krzysztof Wilczyński]

> > > > Even though debugfs_init() failure is not supposed to fail the probe(),
> > > > dwc_pcie_rasdes_debugfs_init() has a devm_kzalloc() and propagating that
> > > > failure would be canolically correct IMO.
> > > 
> > > I'm not sure about this.  What's the requirement to propagate
> > > devm_kzalloc() failures?  I think devres will free any allocs that
> > > were successful regardless.
> > > 
> > > IIUC, we resolved the Gray Hawk Single issue by changing
> > > dwc_pcie_rasdes_debugfs_init() to return success without doing
> > > anything when there's no RAS DES Capability.
> > > 
> > > But dwc_pcie_debugfs_init() can still return failure, and that still
> > > causes dw_pcie_ep_init_registers() to fail, which breaks the "don't
> > > propagate debugfs issues upstream" rule:
> > > 
> > >   int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> > >   {
> > >           ...
> > >           ret = dwc_pcie_debugfs_init(pci);
> > >           if (ret)
> > >                   goto err_remove_edma;
> > > 
> > >           return 0;
> > > 
> > >   err_remove_edma:
> > >           dw_pcie_edma_remove(pci);
> > > 
> > >           return ret;
> > >   }
> > > 
> > > We can say that kzalloc() failure should "never" happen, and therefore
> > > it's OK to fail the driver probe if it happens, but that doesn't seem
> > > like a strong argument for breaking the "don't propagate debugfs
> > > issues" rule.  And someday there may be other kinds of failures from
> > > dwc_pcie_debugfs_init().
> > > 
> > 
> > Fine with me. I was not too sure about propagating failure either.
> 
> What if we do this?
> 
> diff --git i/drivers/pci/controller/dwc/pcie-designware-debugfs.c w/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> index 586a9d107434..fddf71f014c4 100644
> --- i/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> +++ w/drivers/pci/controller/dwc/pcie-designware-debugfs.c
> @@ -162,7 +162,7 @@ void dwc_pcie_debugfs_deinit(struct dw_pcie *pci)
>  	debugfs_remove_recursive(pci->debugfs->debug_dir);
>  }
> 
> -int dwc_pcie_debugfs_init(struct dw_pcie *pci)
> +void dwc_pcie_debugfs_init(struct dw_pcie *pci)
>  {
>  	char dirname[DWC_DEBUGFS_BUF_MAX];
>  	struct device *dev = pci->dev;
> @@ -174,17 +174,15 @@ int dwc_pcie_debugfs_init(struct dw_pcie *pci)
>  	snprintf(dirname, DWC_DEBUGFS_BUF_MAX, "dwc_pcie_%s", dev_name(dev));
>  	dir = debugfs_create_dir(dirname, NULL);
>  	debugfs = devm_kzalloc(dev, sizeof(*debugfs), GFP_KERNEL);
> -	if (!debugfs)
> -		return -ENOMEM;
> +	if (!debugfs) {
> +		dev_err(dev, "failed to allocate memory for debugfs\n");
> +		return;
> +	}
> 
>  	debugfs->debug_dir = dir;
>  	pci->debugfs = debugfs;
>  	err = dwc_pcie_rasdes_debugfs_init(pci, dir);
> -	if (err) {
> -		dev_err(dev, "failed to initialize RAS DES debugfs, err=%d\n",
> -			err);
> -		return err;
> -	}
> -
> -	return 0;
> +	if (err)
> +		dev_warn(dev, "failed to initialize RAS DES debugfs, err=%d",
> +			 err);
>  }
> diff --git i/drivers/pci/controller/dwc/pcie-designware-ep.c w/drivers/pci/controller/dwc/pcie-designware-ep.c
> index c6e76a07c2c9..11ff292ca87d 100644
> --- i/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ w/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -838,9 +838,7 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
> 
>  	dw_pcie_ep_init_non_sticky_registers(pci);
> 
> -	ret = dwc_pcie_debugfs_init(pci);
> -	if (ret)
> -		goto err_remove_edma;
> +	dwc_pcie_debugfs_init(pci);
> 
>  	return 0;
> 
> diff --git i/drivers/pci/controller/dwc/pcie-designware-host.c w/drivers/pci/controller/dwc/pcie-designware-host.c
> index 2081e8c72d12..6501fb062c70 100644
> --- i/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ w/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -548,9 +548,7 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  	if (pp->ops->post_init)
>  		pp->ops->post_init(pp);
> 
> -	ret = dwc_pcie_debugfs_init(pci);
> -	if (ret)
> -		goto err_stop_link;
> +	dwc_pcie_debugfs_init(pci);
> 
>  	return 0;
> 
> diff --git i/drivers/pci/controller/dwc/pcie-designware.h w/drivers/pci/controller/dwc/pcie-designware.h
> index 7f9807d4e5de..dd129718fb41 100644
> --- i/drivers/pci/controller/dwc/pcie-designware.h
> +++ w/drivers/pci/controller/dwc/pcie-designware.h
> @@ -815,12 +815,11 @@ dw_pcie_ep_get_func_from_ep(struct dw_pcie_ep *ep, u8 func_no)
>  #endif
> 
>  #ifdef CONFIG_PCIE_DW_DEBUGFS
> -int dwc_pcie_debugfs_init(struct dw_pcie *pci);
> +void dwc_pcie_debugfs_init(struct dw_pcie *pci);
>  void dwc_pcie_debugfs_deinit(struct dw_pcie *pci);
>  #else
> -static inline int dwc_pcie_debugfs_init(struct dw_pcie *pci)
> +static inline void dwc_pcie_debugfs_init(struct dw_pcie *pci)
>  {
> -	return 0;
>  }
>  static inline void dwc_pcie_debugfs_deinit(struct dw_pcie *pci)
>  {
> 
> I think this would be fine, especially given the rules around debugfs and
> a quick look around Git history to see what the prefernce would be typically.

Changed dev_warn() to dev_err() per Bjorn's feedback off mailing list,
and squashed against the current code on the branch.

Thank you!

	Krzysztof