linux-kernel - Re: [PATCH v7 2/5] PCI: j721e: Add per platform maximum lane settings

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Message-ID: <cd9051ca-9f79-31fc-870d-04dce5139ca9@kernel.org>
Date:   Fri, 25 Nov 2022 14:27:43 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Matt Ranostay <mranostay@...com>, lpieralisi@...nel.org,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        krzysztof.kozlowski@...aro.org, vigneshr@...com,
        tjoseph@...ence.com, sergio.paracuellos@...il.com,
        pthombar@...ence.com, linux-pci@...r.kernel.org
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/5] PCI: j721e: Add per platform maximum lane settings

Hi Matt,

On 24/11/2022 10:12, Matt Ranostay wrote:
> Various platforms have different maximum amount of lanes that can be
> selected. Add max_lanes to struct j721e_pcie to allow for detection of this
> which is needed to calculate the needed bitmask size for the possible lane
> count.
> 
> Signed-off-by: Matt Ranostay <mranostay@...com>
> Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
> ---
>  drivers/pci/controller/cadence/pci-j721e.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> index cc83a8925ce0..8990f58d64d5 100644
> --- a/drivers/pci/controller/cadence/pci-j721e.c
> +++ b/drivers/pci/controller/cadence/pci-j721e.c
> @@ -47,8 +47,6 @@ enum link_status {
>  
>  #define GENERATION_SEL_MASK		GENMASK(1, 0)
>  
> -#define MAX_LANES			2
> -
>  struct j721e_pcie {
>  	struct cdns_pcie	*cdns_pcie;
>  	struct clk		*refclk;
> @@ -71,6 +69,7 @@ struct j721e_pcie_data {
>  	unsigned int		quirk_disable_flr:1;
>  	u32			linkdown_irq_regfield;
>  	unsigned int		byte_access_allowed:1;
> +	unsigned int		max_lanes;
>  };
>  
>  static inline u32 j721e_pcie_user_readl(struct j721e_pcie *pcie, u32 offset)
> @@ -290,11 +289,13 @@ static const struct j721e_pcie_data j721e_pcie_rc_data = {
>  	.quirk_retrain_flag = true,
>  	.byte_access_allowed = false,
>  	.linkdown_irq_regfield = LINK_DOWN,
> +	.max_lanes = 2,
>  };
>  
>  static const struct j721e_pcie_data j721e_pcie_ep_data = {
>  	.mode = PCI_MODE_EP,
>  	.linkdown_irq_regfield = LINK_DOWN,
> +	.max_lanes = 2,
>  };
>  
>  static const struct j721e_pcie_data j7200_pcie_rc_data = {
> @@ -302,23 +303,27 @@ static const struct j721e_pcie_data j7200_pcie_rc_data = {
>  	.quirk_detect_quiet_flag = true,
>  	.linkdown_irq_regfield = J7200_LINK_DOWN,
>  	.byte_access_allowed = true,
> +	.max_lanes = 2,
>  };
>  
>  static const struct j721e_pcie_data j7200_pcie_ep_data = {
>  	.mode = PCI_MODE_EP,
>  	.quirk_detect_quiet_flag = true,
>  	.quirk_disable_flr = true,
> +	.max_lanes = 2,
>  };
>  
>  static const struct j721e_pcie_data am64_pcie_rc_data = {
>  	.mode = PCI_MODE_RC,
>  	.linkdown_irq_regfield = J7200_LINK_DOWN,
>  	.byte_access_allowed = true,
> +	.max_lanes = 1,
>  };
>  
>  static const struct j721e_pcie_data am64_pcie_ep_data = {
>  	.mode = PCI_MODE_EP,
>  	.linkdown_irq_regfield = J7200_LINK_DOWN,
> +	.max_lanes = 1,
>  };
>  
>  static const struct of_device_id of_j721e_pcie_match[] = {
> @@ -432,7 +437,7 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>  	pcie->user_cfg_base = base;
>  
>  	ret = of_property_read_u32(node, "num-lanes", &num_lanes);
> -	if (ret || num_lanes > MAX_LANES)
> +	if (ret || num_lanes > data->max_lanes)
>  		num_lanes = 1;

num_lanes = data->max_lanes; ?

Should we also print an error message saying that invalid num-lanes
was supplied in device tree?
Is it better to error out of probe?

>  	pcie->num_lanes = num_lanes;
>  

cheers,
-roger