[Skiboot] [PATCH] hw/phb4: Rework phb4_get_presence_state()

[Benjamin Herrenschmidt]

On Wed, 2017-05-24 at 12:30 +1000, Gavin Shan wrote:
> There are two issues in current implementation: It should return errcode
> visibile to Linux, which has prefix OPAL_*. The code isn't very obvious.
> 
> This returns OPAL_HARDWARE when the PHB is broken. Otherwise, OPAL_SUCCESS
> is always returned. In the mean while, It refactors the code to make it
> obvious: OPAL_PCI_SLOT_PRESENT is returned when the presence signal (low active)
> or PCIe link is active. Otherwise, OPAL_PCI_SLOT_EMPTY is returned.
> 
> Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>

Acked-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>

> ---
>  hw/phb4.c | 32 +++++++++++---------------------
>  1 file changed, 11 insertions(+), 21 deletions(-)
> 
> diff --git a/hw/phb4.c b/hw/phb4.c
> index 318d934..17685e7 100644
> --- a/hw/phb4.c
> +++ b/hw/phb4.c
> @@ -1844,36 +1844,26 @@ static int64_t phb4_get_presence_state(struct pci_slot *slot, uint8_t *val)
>  	if (p->state == PHB4_STATE_BROKEN)
>  		return OPAL_HARDWARE;
>  
> -	/* Read hotplug status */
> +	/* Check hotplug status */
>  	hps = in_be64(p->regs + PHB_PCIE_HOTPLUG_STATUS);
> -
> -	/* Read link status */
> -	dtctl = in_be64(p->regs + PHB_PCIE_DLP_TRAIN_CTL);
> -
> -	PHBDBG(p, "hp_status=0x%016llx, dlp_train_ctl=0x%016llx\n",
> -	       hps, dtctl);
> -
> -	*val = OPAL_PCI_SLOT_PRESENT;
> -	/* Check presence detect */
> -	if (hps & PHB_PCIE_HPSTAT_PRESENCE) {
> -		/* If it says not present but link is up, then we assume
> +	if (!(hps & PHB_PCIE_HPSTAT_PRESENCE)) {
> +		*val = OPAL_PCI_SLOT_PRESENT;
> +	} else {
> +		/*
> +		 * If it says not present but link is up, then we assume
>  		 * we are on a broken simulation environment and still
>  		 * return a valid presence. Otherwise, not present.
>  		 */
> +		dtctl = in_be64(p->regs + PHB_PCIE_DLP_TRAIN_CTL);
>  		if (dtctl & PHB_PCIE_DLP_TL_LINKACT) {
>  			PHBERR(p, "Presence detect 0 but link set !\n");
> -			return OPAL_SHPC_DEV_PRESENT;
> +			*val = OPAL_PCI_SLOT_PRESENT;
> +		} else {
> +			*val = OPAL_PCI_SLOT_EMPTY;
>  		}
> -		*val = OPAL_PCI_SLOT_EMPTY;
> -		return OPAL_SHPC_DEV_NOT_PRESENT;
>  	}
>  
> -	/*
> -	 * Anything else, we assume device present, the link state
> -	 * machine will perform an early bail out if no electrical
> -	 * signaling is established after a second.
> -	 */
> -	return OPAL_SHPC_DEV_PRESENT;
> +	return OPAL_SUCCESS;
>  }
>  
>  static int64_t phb4_get_link_state(struct pci_slot *slot, uint8_t *val)