Re: [PATCH v21 03/16] PCI: dwc: Add missing PCI_EXP_LNKCAP_MLW handling

[Manivannan Sadhasivam <mani@kernel.org>]

On Fri, Sep 22, 2023 at 03:53:18PM +0900, Yoshihiro Shimoda wrote:
> Update dw_pcie_link_set_max_link_width() to set PCI_EXP_LNKCAP_MLW.
> 
> In accordance with the DW PCIe RC/EP HW manuals [1,2,3,...] aside with
> the PORT_LINK_CTRL_OFF.LINK_CAPABLE and GEN2_CTRL_OFF.NUM_OF_LANES[8:0]
> field there is another one which needs to be updated.
> 
> It's LINK_CAPABILITIES_REG.PCIE_CAP_MAX_LINK_WIDTH. If it isn't done at
> the very least the maximum link-width capability CSR won't expose the
> actual maximum capability.
> 
> [1] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
>     Version 4.60a, March 2015, p.1032
> [2] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
>     Version 4.70a, March 2016, p.1065
> [3] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
>     Version 4.90a, March 2016, p.1057
> ...
> [X] DesignWare Cores PCI Express Controller Databook - DWC PCIe Endpoint,
>       Version 5.40a, March 2019, p.1396
> [X+1] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
>       Version 5.40a, March 2019, p.1266
> 
> [kwilczynski: commit log]
> Link: https://lore.kernel.org/linux-pci/20230825093219.2685912-8-yoshihiro.shimoda.uh@renesas.com
> Suggested-by: Serge Semin <fancer.lancer@gmail.com>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Same comment about s-o-b.

- Mani

> Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
> Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index da4aba4aee62..2b60d20dfdf5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -734,7 +734,8 @@ static void dw_pcie_link_set_max_speed(struct dw_pcie *pci, u32 link_gen)
>  
>  static void dw_pcie_link_set_max_link_width(struct dw_pcie *pci, u32 num_lanes)
>  {
> -	u32 lwsc, plc;
> +	u32 lnkcap, lwsc, plc;
> +	u8 cap;
>  
>  	if (!num_lanes)
>  		return;
> @@ -770,6 +771,12 @@ static void dw_pcie_link_set_max_link_width(struct dw_pcie *pci, u32 num_lanes)
>  	}
>  	dw_pcie_writel_dbi(pci, PCIE_PORT_LINK_CONTROL, plc);
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, lwsc);
> +
> +	cap = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	lnkcap = dw_pcie_readl_dbi(pci, cap + PCI_EXP_LNKCAP);
> +	lnkcap &= ~PCI_EXP_LNKCAP_MLW;
> +	lnkcap |= FIELD_PREP(PCI_EXP_LNKCAP_MLW, num_lanes);
> +	dw_pcie_writel_dbi(pci, cap + PCI_EXP_LNKCAP, lnkcap);
>  }
>  
>  void dw_pcie_iatu_detect(struct dw_pcie *pci)
> -- 
> 2.25.1
> 

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