Re: [PATCH u-boot] dm: pci: Fix handling of errors when scanning device

From: Stefan Roese <sr@denx.de>
To: "Marek Behún" <marek.behun@nic.cz>, "Simon Glass" <sjg@chromium.org>
Cc: u-boot@lists.denx.de, "Pali Rohár" <pali@kernel.org>
Subject: Re: [PATCH u-boot] dm: pci: Fix handling of errors when scanning device
Date: Fri, 10 Sep 2021 09:02:51 +0200	[thread overview]
Message-ID: <1f88ba42-49a9-1c54-db55-8b02963b6c99@denx.de> (raw)
In-Reply-To: <20210907160708.31547-1-marek.behun@nic.cz>

On 07.09.21 18:07, Marek Behún wrote:
> From: Pali Rohár <pali@kernel.org>
> 
> Some PCIe controller's read_config() method support indicating error
> directly via return value, but some cannot distinguish all-ones (or
> all-zeros) read response from an error.
> 
> The current code in pci_bind_bus_devices() interprets all-ones /
> all-zeros in PCI_VENDOR_ID register as "nothing connected", and
> continues the cycle, but an error returned via return value breaks the
> cycle.
> 
> This is wrong for the PCIe controllers which return this error via
> return value.
> 
> Handle all errors when reading PCI_VENDOR_ID the same way.
> 
> This fixes enumeration of PCI devices for example when there is a PCI
> bridge connected behind another PCI bridge and not all ports are
> connected to a device, and the controller (for example Aardvark)
> translates the UR error (Unsupported Request) as -EOPNOTSUPP.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> Signed-off-by: Marek Behún <marek.behun@nic.cz>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

> ---
>   drivers/pci/pci-uclass.c | 9 +--------
>   1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/pci-uclass.c b/drivers/pci/pci-uclass.c
> index ce2eb5da2c..4d0e938fe5 100644
> --- a/drivers/pci/pci-uclass.c
> +++ b/drivers/pci/pci-uclass.c
> @@ -856,10 +856,7 @@ int pci_bind_bus_devices(struct udevice *bus)
>   		/* Check only the first access, we don't expect problems */
>   		ret = pci_bus_read_config(bus, bdf, PCI_VENDOR_ID, &vendor,
>   					  PCI_SIZE_16);
> -		if (ret)
> -			goto error;
> -
> -		if (vendor == 0xffff || vendor == 0x0000)
> +		if (ret || vendor == 0xffff || vendor == 0x0000)
>   			continue;
>   
>   		pci_bus_read_config(bus, bdf, PCI_HEADER_TYPE,
> @@ -940,10 +937,6 @@ int pci_bind_bus_devices(struct udevice *bus)
>   	}
>   
>   	return 0;
> -error:
> -	printf("Cannot read bus configuration: %d\n", ret);
> -
> -	return ret;
>   }
>   
>   static void decode_regions(struct pci_controller *hose, ofnode parent_node,
> 


Viele Grüße,
Stefan

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