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

[Krzysztof Wilczyński]

Hello,

[...]
> > > 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.

Thank you!

	Krzysztof