Re: [PATCH v13 12/22] PCI: dwc: Add dw_pcie_link_set_max_cap_width()

[Manivannan Sadhasivam <mani@kernel.org>]

On Tue, Apr 18, 2023 at 09:23:53PM +0900, Yoshihiro Shimoda wrote:
> Add dw_pcie_link_set_max_cap_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 update. It's

s/update/updated

> 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
> 
> The commit description is suggested by Serge Semin.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index c76fa78c6468..2413cd39310c 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -737,6 +737,21 @@ static void dw_pcie_link_set_max_speed(struct dw_pcie *pci, u32 link_gen)
>  	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, cap | link_speed);
>  }
>  
> +void dw_pcie_link_set_max_cap_width(struct dw_pcie *pci, int num_lanes)

static? Or if you want other drivers to make use of it, then define it as a
common PCI function (not dwc specific) and also update one potential user
(pci-mvebu.c). I think you need to do the later.

- Mani

> +{
> +	u32 val;
> +	u8 cap;
> +
> +	if (!num_lanes)
> +		return;
> +
> +	cap = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	val = dw_pcie_readl_dbi(pci, cap + PCI_EXP_LNKCAP);
> +	val &= ~PCI_EXP_LNKCAP_MLW;
> +	val |= num_lanes << PCI_EXP_LNKSTA_NLW_SHIFT;
> +	dw_pcie_writel_dbi(pci, cap + PCI_EXP_LNKCAP, val);
> +}
> +
>  static void dw_pcie_link_set_max_width(struct dw_pcie *pci, u32 num_lanes)
>  {
>  	u32 val;
> @@ -1073,6 +1088,7 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		dw_pcie_writel_dbi(pci, PCIE_PL_CHK_REG_CONTROL_STATUS, val);
>  	}
>  
> +	dw_pcie_link_set_max_cap_width(pci, pci->num_lanes);
>  	dw_pcie_link_set_max_width(pci, pci->num_lanes);
>  	dw_pcie_link_set_max_link_width(pci, pci->num_lanes);
>  }
> -- 
> 2.25.1
> 

-- 
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