[PATCH v3 10/29] pci: Adjust dm_pci_read_bar32() to return errors correctly

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Mar 30, 2020 at 05:12:46PM -0600, Simon Glass wrote:
> At present if reading a BAR returns 0xffffffff (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.

The above ('the device is not present') is actually not correct.
BAR is not mandatory register and detection is described in PCI spec.

To get device presence one may have check Vendor ID / Device ID pair rather
then BAR.

> Update the function to avoid masking in this case.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
> Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
> ---
> 
> 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 ceb64517047..d2e10d6868a 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 == 0xffffffff)
> +		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.rc2.310.g2932bb562d-goog
> 

-- 
With Best Regards,
Andy Shevchenko