[PATCH] PCI: designware-ep: use ffz() instead of find_first_zero_bit()

[PATCH] PCI: designware-ep: use ffz() instead of find_first_zero_bit()

[Niklas Cassel]

find_first_zero_bit()'s parameter 'size' is defined in bits,
not in bytes.

find_first_zero_bit() was called with bytes rather than bits,
which thus defined a too low upper limit, causing
dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4
and bar 5, which made bar 5 overwrite the settings set by bar 4.

./pcitest.sh
BAR tests
BAR0:		OKAY
BAR1:		OKAY
BAR2:		OKAY
BAR3:		OKAY
BAR4:		NOT OKAY
BAR5:		OKAY

Fix this by using replacing find_first_zero_bit() with ffz(),
since ffz() only works on a single 'unsigned long' and therefore
does not need a size argument.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
---
 drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
index d53d5f168363..ab9a9e160daf 100644
--- a/drivers/pci/dwc/pcie-designware-ep.c
+++ b/drivers/pci/dwc/pcie-designware-ep.c
@@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
 	u32 free_win;
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	free_win = find_first_zero_bit(&ep->ib_window_map,
-				       sizeof(ep->ib_window_map));
+	free_win = ffz(ep->ib_window_map);
 	if (free_win >= ep->num_ib_windows) {
 		dev_err(pci->dev, "no free inbound window\n");
 		return -EINVAL;
@@ -96,8 +95,7 @@ static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep, phys_addr_t phys_addr,
 	u32 free_win;
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	free_win = find_first_zero_bit(&ep->ob_window_map,
-				       sizeof(ep->ob_window_map));
+	free_win = ffz(ep->ob_window_map);
 	if (free_win >= ep->num_ob_windows) {
 		dev_err(pci->dev, "no free outbound window\n");
 		return -EINVAL;
-- 
2.14.2

Re: [PATCH] PCI: designware-ep: use ffz() instead of find_first_zero_bit()

[Lorenzo Pieralisi]

Please follow Bjorn's request for patch formatting:

https://marc.info/?l=linux-pci&m=150905742808166&w=2

I would mention in the commit title that this is a fix.

eg "PCI: designware-ep: Fix find_first_zero_bit() usage"

On Thu, Nov 16, 2017 at 07:34:38PM +0100, Niklas Cassel wrote:
> find_first_zero_bit()'s parameter 'size' is defined in bits,
> not in bytes.
> 
> find_first_zero_bit() was called with bytes rather than bits,

"was called with size in bytes"...

> which thus defined a too low upper limit, causing
> dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4
> and bar 5, which made bar 5 overwrite the settings set by bar 4.
> 
> ./pcitest.sh
> BAR tests
> BAR0:		OKAY
> BAR1:		OKAY
> BAR2:		OKAY
> BAR3:		OKAY
> BAR4:		NOT OKAY
> BAR5:		OKAY

Sorry but this example is pretty much useless - either you add
a self-explanatory kernel log or you just remove it.

> Fix this by using replacing find_first_zero_bit() with ffz(),
> since ffz() only works on a single 'unsigned long' and therefore
> does not need a size argument.
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>

We need a Fixes: tag at least, see Bjorn's post above.

Thanks,
Lorenzo

> ---
>  drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
> index d53d5f168363..ab9a9e160daf 100644
> --- a/drivers/pci/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/dwc/pcie-designware-ep.c
> @@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
>  	u32 free_win;
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  
> -	free_win = find_first_zero_bit(&ep->ib_window_map,
> -				       sizeof(ep->ib_window_map));
> +	free_win = ffz(ep->ib_window_map);
>  	if (free_win >= ep->num_ib_windows) {
>  		dev_err(pci->dev, "no free inbound window\n");
>  		return -EINVAL;
> @@ -96,8 +95,7 @@ static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep, phys_addr_t phys_addr,
>  	u32 free_win;
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  
> -	free_win = find_first_zero_bit(&ep->ob_window_map,
> -				       sizeof(ep->ob_window_map));
> +	free_win = ffz(ep->ob_window_map);
>  	if (free_win >= ep->num_ob_windows) {
>  		dev_err(pci->dev, "no free outbound window\n");
>  		return -EINVAL;
> -- 
> 2.14.2
> 

Re: [PATCH] PCI: designware-ep: use ffz() instead of find_first_zero_bit()

[Joe Perches]

On Fri, 2017-11-17 at 11:38 +0000, Lorenzo Pieralisi wrote:
> Please follow Bjorn's request for patch formatting:
> 
> https://marc.info/?l=linux-pci&m=150905742808166&w=2
> 
> I would mention in the commit title that this is a fix.
> 
> eg "PCI: designware-ep: Fix find_first_zero_bit() usage"
> 
> On Thu, Nov 16, 2017 at 07:34:38PM +0100, Niklas Cassel wrote:
> > find_first_zero_bit()'s parameter 'size' is defined in bits,
> > not in bytes.
> > 
> > find_first_zero_bit() was called with bytes rather than bits,
> 
> "was called with size in bytes"...

This code also uses set_bit/clear_bit.

I suggest not intermixing set_bit/clear_bit calls and ffz
on the same object.

Use either (&/~/ffz) or (set_bit/clear_bit/find_first_zero_bit)

BITS_PER_LONG would work fine for find_first_zero_bit

> > which thus defined a too low upper limit, causing
> > dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4
> > and bar 5, which made bar 5 overwrite the settings set by bar 4.
> > 
> > ./pcitest.sh
> > BAR tests
> > BAR0:		OKAY
> > BAR1:		OKAY
> > BAR2:		OKAY
> > BAR3:		OKAY
> > BAR4:		NOT OKAY
> > BAR5:		OKAY
> 
> Sorry but this example is pretty much useless - either you add
> a self-explanatory kernel log or you just remove it.
> 
> > Fix this by using replacing find_first_zero_bit() with ffz(),
> > since ffz() only works on a single 'unsigned long' and therefore
> > does not need a size argument.
> > 
> > Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> 
> We need a Fixes: tag at least, see Bjorn's post above.
> 
> Thanks,
> Lorenzo
> 
> > ---
> >  drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
> > index d53d5f168363..ab9a9e160daf 100644
> > --- a/drivers/pci/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/dwc/pcie-designware-ep.c
> > @@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
> >  	u32 free_win;
> >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> >  
> > -	free_win = find_first_zero_bit(&ep->ib_window_map,
> > -				       sizeof(ep->ib_window_map));
> > +	free_win = ffz(ep->ib_window_map);
> >  	if (free_win >= ep->num_ib_windows) {
> >  		dev_err(pci->dev, "no free inbound window\n");
> >  		return -EINVAL;
> > @@ -96,8 +95,7 @@ static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep, phys_addr_t phys_addr,
> >  	u32 free_win;
> >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> >  
> > -	free_win = find_first_zero_bit(&ep->ob_window_map,
> > -				       sizeof(ep->ob_window_map));
> > +	free_win = ffz(ep->ob_window_map);
> >  	if (free_win >= ep->num_ob_windows) {
> >  		dev_err(pci->dev, "no free outbound window\n");
> >  		return -EINVAL;
> > -- 
> > 2.14.2
> > 

Re: [PATCH] PCI: designware-ep: use ffz() instead of find_first_zero_bit()

[Lorenzo Pieralisi]

On Tue, Nov 21, 2017 at 08:12:10AM -0800, Joe Perches wrote:
> On Fri, 2017-11-17 at 11:38 +0000, Lorenzo Pieralisi wrote:
> > Please follow Bjorn's request for patch formatting:
> > 
> > https://marc.info/?l=linux-pci&m=150905742808166&w=2
> > 
> > I would mention in the commit title that this is a fix.
> > 
> > eg "PCI: designware-ep: Fix find_first_zero_bit() usage"
> > 
> > On Thu, Nov 16, 2017 at 07:34:38PM +0100, Niklas Cassel wrote:
> > > find_first_zero_bit()'s parameter 'size' is defined in bits,
> > > not in bytes.
> > > 
> > > find_first_zero_bit() was called with bytes rather than bits,
> > 
> > "was called with size in bytes"...
> 
> This code also uses set_bit/clear_bit.
> 
> I suggest not intermixing set_bit/clear_bit calls and ffz
> on the same object.
> 
> Use either (&/~/ffz) or (set_bit/clear_bit/find_first_zero_bit)
> 
> BITS_PER_LONG would work fine for find_first_zero_bit

That would do as a fix and I agree with you that we should not mix the
APIs usage (a check for return value < BITS_PER_LONG should be added too
though).

Actually we can just allocate a bitmap given that we know the bitmap
required size (num_{ib/ob}_windows) and update the find_first_zero_bit()
call with the appropriate size in bits parameter but that can be
a subsequent refactoring patch.

Thanks,
Lorenzo

> > > which thus defined a too low upper limit, causing
> > > dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4
> > > and bar 5, which made bar 5 overwrite the settings set by bar 4.
> > > 
> > > ./pcitest.sh
> > > BAR tests
> > > BAR0:		OKAY
> > > BAR1:		OKAY
> > > BAR2:		OKAY
> > > BAR3:		OKAY
> > > BAR4:		NOT OKAY
> > > BAR5:		OKAY
> > 
> > Sorry but this example is pretty much useless - either you add
> > a self-explanatory kernel log or you just remove it.
> > 
> > > Fix this by using replacing find_first_zero_bit() with ffz(),
> > > since ffz() only works on a single 'unsigned long' and therefore
> > > does not need a size argument.
> > > 
> > > Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> > 
> > We need a Fixes: tag at least, see Bjorn's post above.
> > 
> > Thanks,
> > Lorenzo
> > 
> > > ---
> > >  drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
> > >  1 file changed, 2 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
> > > index d53d5f168363..ab9a9e160daf 100644
> > > --- a/drivers/pci/dwc/pcie-designware-ep.c
> > > +++ b/drivers/pci/dwc/pcie-designware-ep.c
> > > @@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
> > >  	u32 free_win;
> > >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> > >  
> > > -	free_win = find_first_zero_bit(&ep->ib_window_map,
> > > -				       sizeof(ep->ib_window_map));
> > > +	free_win = ffz(ep->ib_window_map);
> > >  	if (free_win >= ep->num_ib_windows) {
> > >  		dev_err(pci->dev, "no free inbound window\n");
> > >  		return -EINVAL;
> > > @@ -96,8 +95,7 @@ static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep, phys_addr_t phys_addr,
> > >  	u32 free_win;
> > >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> > >  
> > > -	free_win = find_first_zero_bit(&ep->ob_window_map,
> > > -				       sizeof(ep->ob_window_map));
> > > +	free_win = ffz(ep->ob_window_map);
> > >  	if (free_win >= ep->num_ob_windows) {
> > >  		dev_err(pci->dev, "no free outbound window\n");
> > >  		return -EINVAL;
> > > -- 
> > > 2.14.2
> > >