Date:   Mon, 6 Jan 2020 14:02:59 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com, robh+dt@...nel.org,
        jonathanh@...dia.com, andrew.murray@....com, kishon@...com,
        gustavo.pimentel@...opsys.com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V2 3/5] PCI: tegra: Add support for PCIe endpoint mode in
 Tegra194

On Fri, Jan 03, 2020 at 06:14:02PM +0530, Vidya Sagar wrote:
> Add support for the endpoint mode of Synopsys DesignWare core based
> dual mode PCIe controllers present in Tegra194 SoC.
> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> ---
> V2:
> * Addressed Bjorn's review comments
> * Made changes as part of addressing review comments for other patches
> 
>  drivers/pci/controller/dwc/Kconfig         |  30 +-
>  drivers/pci/controller/dwc/pcie-tegra194.c | 782 ++++++++++++++++++++-
>  2 files changed, 796 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
[...]
> @@ -411,11 +466,66 @@ static irqreturn_t tegra_pcie_rp_irq_handler(struct tegra_pcie_dw *pcie)
>  	return IRQ_HANDLED;
>  }
>  
> +static irqreturn_t tegra_pcie_ep_irq_handler(struct tegra_pcie_dw *pcie)
> +{
> +	struct dw_pcie_ep *ep = &pcie->pci.ep;
> +	int spurious = 1;
> +	u32 val, tmp;
> +
> +	val = appl_readl(pcie, APPL_INTR_STATUS_L0);
> +	if (val & APPL_INTR_STATUS_L0_LINK_STATE_INT) {
> +		val = appl_readl(pcie, APPL_INTR_STATUS_L1_0_0);
> +		appl_writel(pcie, val, APPL_INTR_STATUS_L1_0_0);
> +		if (val & APPL_INTR_STATUS_L1_0_0_HOT_RESET_DONE) {
> +			/* clear any stale PEX_RST interrupt */
> +			if (!kfifo_put(&pcie->event_fifo, EP_HOT_RST_DONE)) {
> +				dev_err(pcie->dev, "EVENT FIFO is full\n");
> +				return IRQ_HANDLED;
> +			}
> +			wake_up(&pcie->wq);
> +		}

Overall this patch looks a little cluttered. A few blank lines before
and after (or between) block statements would help make this more
readable, in my opinion.

> +		if (val & APPL_INTR_STATUS_L1_0_0_RDLH_LINK_UP_CHGED) {
> +			tmp = appl_readl(pcie, APPL_LINK_STATUS);
> +			if (tmp & APPL_LINK_STATUS_RDLH_LINK_UP) {
> +				dev_info(pcie->dev, "Link is up with Host\n");

Do we want this to be an info message? Looks to me like this is mostly
useful for debug purposes, as a quick way to check if the link is up.
For production use, this would perhaps be better to expose as a sysfs
attribute so that userspace can query it at runtime rather than search
through kernel logs.

> +				dw_pcie_ep_linkup(ep);
> +			}
> +		}
> +		spurious = 0;
> +	}
> +
> +	if (val & APPL_INTR_STATUS_L0_PCI_CMD_EN_INT) {
> +		val = appl_readl(pcie, APPL_INTR_STATUS_L1_15);
> +		appl_writel(pcie, val, APPL_INTR_STATUS_L1_15);
> +		if (val & APPL_INTR_STATUS_L1_15_CFG_BME_CHGED) {
> +			if (!kfifo_put(&pcie->event_fifo, EP_BME_CHANGE)) {
> +				dev_err(pcie->dev, "EVENT FIFO is full\n");
> +				return IRQ_HANDLED;
> +			}
> +			wake_up(&pcie->wq);
> +		}
> +		spurious = 0;
> +	}
> +
> +	if (spurious) {
> +		dev_warn(pcie->dev, "Random interrupt (STATUS = 0x%08X)\n",
> +			 val);
> +		appl_writel(pcie, val, APPL_INTR_STATUS_L0);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static irqreturn_t tegra_pcie_irq_handler(int irq, void *arg)
>  {
>  	struct tegra_pcie_dw *pcie = arg;
>  
> -	return tegra_pcie_rp_irq_handler(pcie);
> +	if (pcie->mode == DW_PCIE_RC_TYPE)
> +		return tegra_pcie_rp_irq_handler(pcie);
> +	else if (pcie->mode == DW_PCIE_EP_TYPE)
> +		return tegra_pcie_ep_irq_handler(pcie);
> +
> +	return IRQ_NONE;
>  }

We already know at probe time whether the controller is in root complex
or endpoint mode, right? Couldn't we just install the correct handler
rather than multiplex here? It's not a very big deal, but given that
these are interrupts, avoiding the additional indirection might be a
good idea.

[...]
> @@ -986,6 +1115,42 @@ static int tegra_pcie_dw_parse_dt(struct tegra_pcie_dw *pcie)
>  	pcie->enable_cdm_check =
>  		of_property_read_bool(np, "snps,enable-cdm-check");
>  
> +	if (pcie->mode == DW_PCIE_RC_TYPE)
> +		return 0;
> +
> +	/* Endpoint mode specific DT entries */
> +	name = devm_kasprintf(pcie->dev, GFP_KERNEL,
> +			      "tegra_pcie_%u_pex_rst_gpio", pcie->cid);
> +	if (!name) {
> +		dev_err(pcie->dev, "Failed to create PERST GPIO string\n");
> +		return -ENOMEM;
> +	}
> +	pcie->pex_rst_gpiod = devm_gpiod_get_from_of_node(pcie->dev, np,

If np == pcie->dev.of_node, you can simply use devm_gpiod_get() here,
can't you?

[...]
> +static void pex_ep_event_hot_rst_done(struct tegra_pcie_dw *pcie)
> +{
> +	u32 val = 0;

The initialization here seems unnecessary.

[...]
> +static int tegra_pcie_ep_raise_legacy_irq(struct tegra_pcie_dw *pcie, u16 irq)
> +{
> +	/* Tegra194 supports only INTA */
> +	if (irq > 1)
> +		return -EINVAL;
> +
> +	appl_writel(pcie, 1, APPL_LEGACY_INTX);
> +	mdelay(1);

Spinning for 1 ms these days is quite a lot. Does this have to be a busy
loop or could you use something like usleep_range(1000, 2000) to allow
the CPU to do something else in the meantime?

Also, does the legacy INTX pulse have to be a whole millisecond wide? Or
could this be shorter? A one millisecond pulse implies a maximum of 1000
interrupts per second, which seems a bit low.

> @@ -1440,6 +2178,12 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
>  	int ret;
>  	u32 i;
>  
> +	match = of_match_device(of_match_ptr(tegra_pcie_dw_of_match), dev);
> +	if (!match)
> +		return -EINVAL;
> +
> +	data = (struct tegra_pcie_dw_of_data *)match->data;

of_device_get_match_data()?

> +
>  	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
>  	if (!pcie)
>  		return -ENOMEM;
> @@ -1449,6 +2193,7 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
>  	pci->ops = &tegra_dw_pcie_ops;
>  	pp = &pci->pp;
>  	pcie->dev = &pdev->dev;
> +	pcie->mode = (enum dw_pcie_device_mode)data->mode;
>  
>  	ret = tegra_pcie_dw_parse_dt(pcie);
>  	if (ret < 0) {
> @@ -1462,6 +2207,9 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	if (pcie->pex_refclk_sel_gpiod)
> +		gpiod_set_value(pcie->pex_refclk_sel_gpiod, 1);
> +
>  	pcie->pex_ctl_supply = devm_regulator_get(dev, "vddio-pex-ctl");
>  	if (IS_ERR(pcie->pex_ctl_supply)) {
>  		ret = PTR_ERR(pcie->pex_ctl_supply);
> @@ -1570,11 +2318,24 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, pcie);
>  
> -	ret = tegra_pcie_config_rp(pcie);
> -	if (ret && ret != -ENOMEDIUM)
> -		goto fail;
> -	else
> -		return 0;
> +	switch (pcie->mode) {
> +	case DW_PCIE_RC_TYPE:
> +		ret = tegra_pcie_config_rp(pcie);
> +		if (ret && ret != -ENOMEDIUM)
> +			goto fail;
> +		else
> +			return 0;
> +		break;
> +
> +	case DW_PCIE_EP_TYPE:
> +		ret = tegra_pcie_config_ep(pcie, pdev);
> +		if (ret < 0)
> +			goto fail;
> +		break;
> +
> +	default:
> +		dev_err(dev, "Invalid PCIe device type %d\n", pcie->mode);
> +	}
>  
>  fail:
>  	tegra_bpmp_put(pcie->bpmp);
> @@ -1593,6 +2354,8 @@ static int tegra_pcie_dw_remove(struct platform_device *pdev)
>  	pm_runtime_put_sync(pcie->dev);
>  	pm_runtime_disable(pcie->dev);
>  	tegra_bpmp_put(pcie->bpmp);
> +	if (pcie->pex_refclk_sel_gpiod)
> +		gpiod_set_value(pcie->pex_refclk_sel_gpiod, 0);
>  
>  	return 0;
>  }
> @@ -1697,13 +2460,6 @@ static void tegra_pcie_dw_shutdown(struct platform_device *pdev)
>  	__deinit_controller(pcie);
>  }
>  
> -static const struct of_device_id tegra_pcie_dw_of_match[] = {
> -	{
> -		.compatible = "nvidia,tegra194-pcie",
> -	},
> -	{},
> -};
> -

No need to move this around if you use of_device_get_match_data().

Thierry

>  static const struct dev_pm_ops tegra_pcie_dw_pm_ops = {
>  	.suspend_late = tegra_pcie_dw_suspend_late,
>  	.suspend_noirq = tegra_pcie_dw_suspend_noirq,
> -- 
> 2.17.1
> 

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