diff mbox series

[2/2] PCI: pciehp: Fix wrong failure check on pcie_capability_read_*()

Message ID 20200619201219.32126-3-refactormyself@gmail.com
State New
Headers show
Series Fix wrong failure check on pcie_capability_read_*() | expand

Commit Message

Saheed Bolarinwa June 19, 2020, 8:12 p.m. UTC
From: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>

On failure, pcie_capabiility_read_*() will set the status value,
its last parameter to 0 and not ~0.
This bug fix checks for the proper value.

Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
---
 drivers/pci/hotplug/pciehp_hpc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Lukas Wunner June 20, 2020, 9:09 a.m. UTC | #1
On Fri, Jun 19, 2020 at 10:12:19PM +0200, refactormyself@gmail.com wrote:
> On failure, pcie_capabiility_read_*() will set the status value,
> its last parameter to 0 and not ~0.
> This bug fix checks for the proper value.

If a config space read times out, the PCIe controller fabricates
an "all ones" response.  The code is checking for such a timeout,
not for an error.  Hence the code is fine.

Thanks,

Lukas

> 
> Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 53433b37e181..c1a67054948a 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -89,7 +89,7 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout)
>  
>  	do {
>  		pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
> -		if (slot_status == (u16) ~0) {
> +		if (slot_status == (u16)0) {
>  			ctrl_info(ctrl, "%s: no response from device\n",
>  				  __func__);
>  			return 0;
> @@ -165,7 +165,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
>  	pcie_wait_cmd(ctrl);
>  
>  	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
> -	if (slot_ctrl == (u16) ~0) {
> +	if (slot_ctrl == (u16)0) {
>  		ctrl_info(ctrl, "%s: no response from device\n", __func__);
>  		goto out;
>  	}
> @@ -236,7 +236,7 @@ int pciehp_check_link_active(struct controller *ctrl)
>  	int ret;
>  
>  	ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> -	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)~0)
> +	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)0)
>  		return -ENODEV;
>  
>  	ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> @@ -440,7 +440,7 @@ int pciehp_card_present(struct controller *ctrl)
>  	int ret;
>  
>  	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
> -	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)~0)
> +	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)0)
>  		return -ENODEV;
>  
>  	return !!(slot_status & PCI_EXP_SLTSTA_PDS);
> @@ -592,7 +592,7 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
>  
>  read_status:
>  	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
> -	if (status == (u16) ~0) {
> +	if (status == (u16)0) {
>  		ctrl_info(ctrl, "%s: no response from device\n", __func__);
>  		if (parent)
>  			pm_runtime_put(parent);
> -- 
> 2.18.2
Bjorn Helgaas June 26, 2020, 7:14 p.m. UTC | #2
On Sat, Jun 20, 2020 at 11:09:36AM +0200, Lukas Wunner wrote:
> On Fri, Jun 19, 2020 at 10:12:19PM +0200, refactormyself@gmail.com wrote:
> > On failure, pcie_capabiility_read_*() will set the status value,
> > its last parameter to 0 and not ~0.
> > This bug fix checks for the proper value.
> 
> If a config space read times out, the PCIe controller fabricates
> an "all ones" response.  The code is checking for such a timeout,
> not for an error.  Hence the code is fine.

In the typical case, the pci_read_config_word() done by
pcie_capability_read_word() will not return an error, so if the read
times out, we should see slot_status == ~0.

But if it's possible to set dev->error_state ==
pci_channel_io_perm_failure, pci_read_config_word() will return an
error because pci_dev_is_disconnected(), so slot_status would be 0.

There are a dozen or so places that set dev->error_state.  It doesn't
look *likely* that any of them would cause this, but it doesn't
instill confidence.

It would be a lot nicer if we didn't have to worry about both the 0
and ~0 cases.  I keep coming back to the idea of removing the "*val
= 0" code from pcie_capability_read_word() so we wouldn't have that
special case.

In any case, this particular patch doesn't seem like quite the right
fix, so I'll drop it.

> > Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
> > ---
> >  drivers/pci/hotplug/pciehp_hpc.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> > index 53433b37e181..c1a67054948a 100644
> > --- a/drivers/pci/hotplug/pciehp_hpc.c
> > +++ b/drivers/pci/hotplug/pciehp_hpc.c
> > @@ -89,7 +89,7 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout)
> >  
> >  	do {
> >  		pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
> > -		if (slot_status == (u16) ~0) {
> > +		if (slot_status == (u16)0) {
> >  			ctrl_info(ctrl, "%s: no response from device\n",
> >  				  __func__);
> >  			return 0;
> > @@ -165,7 +165,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
> >  	pcie_wait_cmd(ctrl);
> >  
> >  	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
> > -	if (slot_ctrl == (u16) ~0) {
> > +	if (slot_ctrl == (u16)0) {
> >  		ctrl_info(ctrl, "%s: no response from device\n", __func__);
> >  		goto out;
> >  	}
> > @@ -236,7 +236,7 @@ int pciehp_check_link_active(struct controller *ctrl)
> >  	int ret;
> >  
> >  	ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> > -	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)~0)
> > +	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)0)
> >  		return -ENODEV;
> >  
> >  	ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> > @@ -440,7 +440,7 @@ int pciehp_card_present(struct controller *ctrl)
> >  	int ret;
> >  
> >  	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
> > -	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)~0)
> > +	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)0)
> >  		return -ENODEV;
> >  
> >  	return !!(slot_status & PCI_EXP_SLTSTA_PDS);
> > @@ -592,7 +592,7 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> >  
> >  read_status:
> >  	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
> > -	if (status == (u16) ~0) {
> > +	if (status == (u16)0) {
> >  		ctrl_info(ctrl, "%s: no response from device\n", __func__);
> >  		if (parent)
> >  			pm_runtime_put(parent);
> > -- 
> > 2.18.2
diff mbox series

Patch

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 53433b37e181..c1a67054948a 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -89,7 +89,7 @@  static int pcie_poll_cmd(struct controller *ctrl, int timeout)
 
 	do {
 		pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
-		if (slot_status == (u16) ~0) {
+		if (slot_status == (u16)0) {
 			ctrl_info(ctrl, "%s: no response from device\n",
 				  __func__);
 			return 0;
@@ -165,7 +165,7 @@  static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 	pcie_wait_cmd(ctrl);
 
 	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
-	if (slot_ctrl == (u16) ~0) {
+	if (slot_ctrl == (u16)0) {
 		ctrl_info(ctrl, "%s: no response from device\n", __func__);
 		goto out;
 	}
@@ -236,7 +236,7 @@  int pciehp_check_link_active(struct controller *ctrl)
 	int ret;
 
 	ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
-	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)~0)
+	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)0)
 		return -ENODEV;
 
 	ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
@@ -440,7 +440,7 @@  int pciehp_card_present(struct controller *ctrl)
 	int ret;
 
 	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
-	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)~0)
+	if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)0)
 		return -ENODEV;
 
 	return !!(slot_status & PCI_EXP_SLTSTA_PDS);
@@ -592,7 +592,7 @@  static irqreturn_t pciehp_isr(int irq, void *dev_id)
 
 read_status:
 	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
-	if (status == (u16) ~0) {
+	if (status == (u16)0) {
 		ctrl_info(ctrl, "%s: no response from device\n", __func__);
 		if (parent)
 			pm_runtime_put(parent);