Re: [PATCH] PCI: rockchip: check link status when validating device

[Brian Norris <briannorris@chromium.org>]

On Fri, May 19, 2017 at 02:58:27PM +0800, Shawn Lin wrote:
> This patch checks the link status before reading and
> writing configure space of devices attached to the RC.
> If the link status is down, we shouldn't try to access
> the devices.

I'm curious, in what situations are you seeing the link down? In all the
cases where I can manage to screw up my endpoint and see system aborts
due to config accesses, this check still says the link is up. Presumably
you have some test cases that benefit from this though.

> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> ---
> 
>  drivers/pci/host/pcie-rockchip.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
> index 0e020b6..1e64227 100644
> --- a/drivers/pci/host/pcie-rockchip.c
> +++ b/drivers/pci/host/pcie-rockchip.c
> @@ -275,9 +275,21 @@ static void rockchip_pcie_update_txcredit_mui(struct rockchip_pcie *rockchip)
>  	rockchip_pcie_write(rockchip, val, PCIE_CORE_TXCREDIT_CFG1);
>  }
>  
> +static inline bool rockchip_pcie_link_up(struct rockchip_pcie *rockchip)
> +{
> +	return PCIE_LINK_UP(rockchip_pcie_read(rockchip,
> +					PCIE_CLIENT_BASIC_STATUS1));
> +}
> +
>  static int rockchip_pcie_valid_device(struct rockchip_pcie *rockchip,
>  				      struct pci_bus *bus, int dev)
>  {
> +	/* do not access the devices if the link isn't completed */
> +	if (bus->number != rockchip->root_bus_nr) {
> +		if (!rockchip_pcie_link_up(rockchip))
> +			return 0;
> +	}

Seems like this should be the last check in the function, after you
check that the bus and dev numbers are reasonable?

Brian

> +
>  	/* access only one slot on each root port */
>  	if (bus->number == rockchip->root_bus_nr && dev > 0)
>  		return 0;
> -- 
> 1.9.1
> 
>