Re: [PATCH v16 11/22] PCI: dwc: Add dw_pcie_link_set_max_cap_width()

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On Wed, May 10, 2023 at 03:22:23PM +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 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
> 
> The commit description is suggested by Serge Semin.
> 
> Suggested-by: Serge Semin <fancer.lancer@xxxxxxxxx>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> ---
>  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 5dc423dd2f21..8b2978c6eb23 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -758,6 +758,21 @@ static void dw_pcie_link_set_max_link_width(struct dw_pcie *pci, u32 num_lanes)
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, lwsc);
>  }
>  
> +static void dw_pcie_link_set_max_cap_width(struct dw_pcie *pci, int num_lanes)
> +{

> +	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);

Once again. Please move this code to the
dw_pcie_link_set_max_link_width() method as I already asked here:
https://lore.kernel.org/linux-pci/20230501195753.o3qfcs7qyergccnr@mobilestation/
There is no point in creating a separate method for the action which
is implied by the already defined and incomplete
dw_pcie_link_set_max_link_width() function.

Also as we already agreed please replace the hard-coded bitwise shift
operation with the FIELD_PREP(PCI_EXP_LNKCAP_MLW, num_lanes)
statement.

-Serge(y)

> +}
> +
>  void dw_pcie_iatu_detect(struct dw_pcie *pci)
>  {
>  	int max_region, ob, ib;
> @@ -1040,4 +1055,5 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  	dw_pcie_writel_dbi(pci, PCIE_PORT_LINK_CONTROL, val);
>  
>  	dw_pcie_link_set_max_link_width(pci, pci->num_lanes);
> +	dw_pcie_link_set_max_cap_width(pci, pci->num_lanes);
>  }
> -- 
> 2.25.1
> 



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