[PATCH v5 10/29] pci: Adjust dm_pci_read_bar32() to return errors correctly
At present if reading a BAR returns 0x (e.g. the device is not present) then the value is masked and a different value is returned. This makes it harder to detect the problem when debugging. Update the function to avoid masking in this case. Signed-off-by: Simon Glass Reviewed-by: Bin Meng Reviewed-by: Wolfgang Wallner --- Changes in v5: None Changes in v4: None Changes in v3: None Changes in v2: None drivers/pci/pci-uclass.c | 9 - 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci-uclass.c b/drivers/pci/pci-uclass.c index 213381da6bd..7f46e901fb2 100644 --- a/drivers/pci/pci-uclass.c +++ b/drivers/pci/pci-uclass.c @@ -1213,7 +1213,14 @@ u32 dm_pci_read_bar32(const struct udevice *dev, int barnum) bar = PCI_BASE_ADDRESS_0 + barnum * 4; dm_pci_read_config32(dev, bar, &addr); - if (addr & PCI_BASE_ADDRESS_SPACE_IO) + + /* +* If we get an invalid address, return this so that comparisons with +* FDT_ADDR_T_NONE work correctly +*/ + if (addr == 0x) + return addr; + else if (addr & PCI_BASE_ADDRESS_SPACE_IO) return addr & PCI_BASE_ADDRESS_IO_MASK; else return addr & PCI_BASE_ADDRESS_MEM_MASK; -- 2.26.0.292.g33ef6b2f38-goog
Re: [PATCH v5 10/29] pci: Adjust dm_pci_read_bar32() to return errors correctly
On Thu, Apr 9, 2020 at 2:00 AM Simon Glass wrote: > > At present if reading a BAR returns 0x (e.g. the device is not > present) then the value is masked and a different value is returned. > This makes it harder to detect the problem when debugging. If you insisting on the code, you may need to reword the commit message, at least by removing ambiguous "device not present", because this is not how PCI spec defines situations when device is not present. -- With Best Regards, Andy Shevchenko
Re: [PATCH v5 10/29] pci: Adjust dm_pci_read_bar32() to return errors correctly
> From: Andy Shevchenko > Date: Thu, 9 Apr 2020 12:06:11 +0300 > > On Thu, Apr 9, 2020 at 2:00 AM Simon Glass wrote: > > > > At present if reading a BAR returns 0x (e.g. the device is not > > present) then the value is masked and a different value is returned. > > This makes it harder to detect the problem when debugging. > > If you insisting on the code, you may need to reword the commit > message, at least by removing ambiguous "device not present", because > this is not how PCI spec defines situations when device is not > present. In addition to that: The 0x value is an artifact of how x86 systems handle aborted PCI transactions. Other architectures will probably generate a fault of some sorts. It looks like at least some of the pci drivers in u-boot emulate the x86 behaviour but I'm not sure all of them do.
Re: [PATCH v5 10/29] pci: Adjust dm_pci_read_bar32() to return errors correctly
Hi, On Thu, 9 Apr 2020 at 03:39, Mark Kettenis wrote: > > > From: Andy Shevchenko > > Date: Thu, 9 Apr 2020 12:06:11 +0300 > > > > On Thu, Apr 9, 2020 at 2:00 AM Simon Glass wrote: > > > > > > At present if reading a BAR returns 0x (e.g. the device is not > > > present) then the value is masked and a different value is returned. > > > This makes it harder to detect the problem when debugging. > > > > If you insisting on the code, you may need to reword the commit > > message, at least by removing ambiguous "device not present", because > > this is not how PCI spec defines situations when device is not > > present. > > In addition to that: > > The 0x value is an artifact of how x86 systems handle aborted > PCI transactions. Other architectures will probably generate a fault > of some sorts. It looks like at least some of the pci drivers in > u-boot emulate the x86 behaviour but I'm not sure all of them do. This is not intended to be used to detect missing devices. It's just that we should not be masking an obviously invalid value, to make it look more valid. It is very confusing. I'll update the comment message. Regards, Simon
