Re: [PATCH v2 05/10] PCI: tegra194: Check for 16 GT/s capability before programming

[Frank Li <Frank.li@oss.nxp.com>]

On Wed, Oct 21, 2026 at 11:43:44AM +0530, Manikanta Maddireddy wrote:
> config_gen3_gen4_eq_presets() added PCI_PL_16GT_LE_CTRL to the result of
> dw_pcie_find_ext_capability() without checking whether the 16 GT/s
> capability exists. If the capability is absent, the code writes lane
> presets at an unrelated configuration offset.
>
> Look up the capability once before the lane loop and skip the 16 GT/s lane
> equivalent control programming when it is absent.
>
> Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> Changes V1 -> V2: None
>
>  drivers/pci/controller/dwc/pcie-tegra194.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index fb8084cef38b..14031cfaee8b 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -840,7 +840,11 @@ static void tegra_pcie_enable_interrupts(struct dw_pcie_rp *pp)
>  static void config_gen3_gen4_eq_presets(struct tegra_pcie_dw *pcie)
>  {
>  	struct dw_pcie *pci = &pcie->pci;
> -	u32 val, offset, i;
> +	u32 pl16g, val, i;
> +
> +	pl16g = dw_pcie_find_ext_capability(pci, PCI_EXT_CAP_ID_PL_16GT);
> +	if (pl16g)
> +		pl16g += PCI_PL_16GT_LE_CTRL;
>
>  	/* Program init preset */
>  	for (i = 0; i < pcie->num_lanes; i++) {
> @@ -851,15 +855,15 @@ static void config_gen3_gen4_eq_presets(struct tegra_pcie_dw *pcie)
>  			     GEN3_GEN4_EQ_PRESET_INIT);
>  		dw_pcie_writew_dbi(pci, CAP_SPCIE_CAP_OFF + (i * 2), val);
>
> -		offset = dw_pcie_find_ext_capability(pci,
> -						     PCI_EXT_CAP_ID_PL_16GT) +
> -				PCI_PL_16GT_LE_CTRL;
> -		val = dw_pcie_readb_dbi(pci, offset + i);
> +		if (!pl16g)
> +			continue;
> +
> +		val = dw_pcie_readb_dbi(pci, pl16g + i);
>  		FIELD_MODIFY(PCI_PL_16GT_LE_CTRL_DSP_TX_PRESET_MASK, &val,
>  			     GEN3_GEN4_EQ_PRESET_INIT);
>  		FIELD_MODIFY(PCI_PL_16GT_LE_CTRL_USP_TX_PRESET_MASK, &val,
>  			     GEN3_GEN4_EQ_PRESET_INIT);
> -		dw_pcie_writeb_dbi(pci, offset + i, val);
> +		dw_pcie_writeb_dbi(pci, pl16g + i, val);
>  	}
>
>  	val = dw_pcie_readl_dbi(pci, GEN3_CTRL);
> --
> 2.34.1
>