Re: [PATCH 07/10] pnv/phb4: Set link speed and width in the DLP training control register

[Cédric Le Goater]

On 3/21/24 11:04, Saif Abrar wrote:
> Get the current link-status from PCIE macro.
> Extract link-speed and link-width from the link-status
> and set in the DLP training control (PCIE_DLP_TCR) register.
>
> Signed-off-by: Saif Abrar <saif.abrar@linux.vnet.ibm.com>

Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.


> ---
>   hw/pci-host/pnv_phb4.c | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
> index 7b3d75bae6..6823ffab54 100644
> --- a/hw/pci-host/pnv_phb4.c
> +++ b/hw/pci-host/pnv_phb4.c
> @@ -980,10 +980,27 @@ static uint64_t pnv_phb4_reg_read(void *opaque, hwaddr 
> off, unsigned size)
>           val |= PHB_PCIE_SCR_PLW_X16; /* RO bit */
>           break;
>   
> -    /* Link training always appears trained */
>       case PHB_PCIE_DLP_TRAIN_CTL:
> -        /* TODO: Do something sensible with speed ? */
> +        /* Link training always appears trained */
>           val |= PHB_PCIE_DLP_INBAND_PRESENCE | PHB_PCIE_DLP_TL_LINKACT;
> +
> +        /* Get the current link-status from PCIE */
> +        uint32_t exp_offset = get_exp_offset(phb);
> +        uint32_t lnkstatus = bswap32(pnv_phb4_rc_config_read(phb,
> +                                exp_offset + PCI_EXP_LNKSTA, 4));
> +
> +        /* Extract link-speed from the link-status */
> +        uint32_t v = lnkstatus & PCI_EXP_LNKSTA_CLS;
> +        /* Set the current link-speed at the LINK_SPEED position */
> +        val = SETFIELD(PHB_PCIE_DLP_LINK_SPEED, val, v);
> +
> +        /*
> +         * Extract link-width from the link-status,
> +         * after shifting the required bitfields.
> +         */
> +        v = (lnkstatus & PCI_EXP_LNKSTA_NLW) >> PCI_EXP_LNKSTA_NLW_SHIFT;
> +        /* Set the current link-width at the LINK_WIDTH position */
> +        val = SETFIELD(PHB_PCIE_DLP_LINK_WIDTH, val, v);
>           return val;
>   
>       /*