Re: [RFC PATCH net-next 06/12] PCI: Add debug print for device ready delay

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Oct 17, 2023 at 10:42:51AM +0300, Ido Schimmel wrote:
> Currently, the time it took a PCI device to become ready after reset is
> only printed if it was longer than 1000ms ('PCI_RESET_WAIT'). However,
> for debugging purposes it is useful to know this time even if it was
> shorter. For example, with the device I am working on, hardware
> engineers asked to verify that it becomes ready on the first try (no
> delay).
> 
> To that end, add a debug level print that can be enabled using dynamic
> debug. Example:
> 
>  # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
>  # dmesg -c | grep ready
>  # echo "file drivers/pci/pci.c +p" > /sys/kernel/debug/dynamic_debug/control
>  # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
>  # dmesg -c | grep ready
>  [  396.060335] mlxsw_spectrum4 0000:01:00.0: ready 0ms after link toggle
>  # echo "file drivers/pci/pci.c -p" > /sys/kernel/debug/dynamic_debug/control
>  # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
>  # dmesg -c | grep ready
> 
> Signed-off-by: Ido Schimmel <idosch@nvidia.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/pci/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 59c01d68c6d5..0a708e65c5c4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1216,6 +1216,9 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
>  	if (delay > PCI_RESET_WAIT)
>  		pci_info(dev, "ready %dms after %s\n", delay - 1,
>  			 reset_type);
> +	else
> +		pci_dbg(dev, "ready %dms after %s\n", delay - 1,
> +			reset_type);
>  
>  	return 0;
>  }
> -- 
> 2.40.1
>