linux-kernel - Re: [PATCH v2 10/10] PCIe: qcom: add Force GEN1 support

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Date:   Fri, 3 Apr 2020 12:01:01 +0300
From:   Stanimir Varbanov <svarbanov@...sol.com>
To:     Ansuel Smith <ansuelsmth@...il.com>, Andy Gross <agross@...nel.org>
Cc:     Sham Muthayyan <smuthayy@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/10] PCIe: qcom: add Force GEN1 support

Hi Ansuel,

On 4/2/20 3:11 PM, Ansuel Smith wrote:
> From: Sham Muthayyan <smuthayy@...eaurora.org>
> 
> Add Force GEN1 support needed in some ipq806x board
> that needs to limit some pcie line to gen1 for some
> hardware limitation.
> This is set by the max-link-speed dts entry and needed
> by some soc based on ipq806x. (for example Netgear R7800
> router)
> 
> Signed-off-by: Sham Muthayyan <smuthayy@...eaurora.org>
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 8047ac7dc8c7..2212e9498b91 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -27,6 +27,7 @@
>  #include <linux/slab.h>
>  #include <linux/types.h>
>  
> +#include "../../pci.h"

This looks suspiciously (even ugly), but I saw that the other users of
of_pci_get_max_link_speed is doing the same.

Bjorn H. : do you know why the prototype is there? Perhaps it must be in
linux/of_pci.h.

>  #include "pcie-designware.h"
>  
>  #define PCIE20_PARF_SYS_CTRL			0x00
> @@ -99,6 +100,8 @@
>  #define PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE	0x358
>  #define SLV_ADDR_SPACE_SZ			0x10000000
>  
> +#define PCIE20_LNK_CONTROL2_LINK_STATUS2        0xA0

tabs instead of spaces and hex numbers should be lower-case

> +
>  #define DEVICE_TYPE_RC				0x4
>  
>  #define QCOM_PCIE_2_1_0_MAX_SUPPLY	3
> @@ -199,6 +202,7 @@ struct qcom_pcie {
>  	struct phy *phy;
>  	struct gpio_desc *reset;
>  	const struct qcom_pcie_ops *ops;
> +	bool force_gen1;

could you rename this and make it int:

	int gen;

>  };
>  
>  #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
> @@ -441,6 +445,11 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
>  
>  	/* wait for clock acquisition */
>  	usleep_range(1000, 1500);

add a blank line here

> +	if (pcie->force_gen1) {

	if (pcie->gen == 1) {

> +		writel_relaxed((readl_relaxed(
> +		  pcie->pci->dbi_base + PCIE20_LNK_CONTROL2_LINK_STATUS2) | 1),
> +		  pcie->pci->dbi_base + PCIE20_LNK_CONTROL2_LINK_STATUS2);
> +	}

why you are using writel/readl_relaxed ?

Also could you split the line to two:

	val = read()
	write(val | 1, address)

>  
>  
>  	/* Set the Max TLP size to 2K, instead of using default of 4K */
> @@ -1440,6 +1449,10 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>  		goto err_pm_runtime_put;
>  	}
>  
> +	ret = of_pci_get_max_link_speed(pdev->dev.of_node);> +	if (ret == 1)
> +		pcie->force_gen1 = true;

drop this, handle ret < 0 and default to generation 2

	pcie->gen = of_pci_get_max_link_speed(pdev->dev.of_node);
	if (pcie->gen < 0)
		pcie->gen = 2;

> +
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "parf");
>  	pcie->parf = devm_ioremap_resource(dev, res);
>  	if (IS_ERR(pcie->parf)) {
> 

-- 
regards,
Stan