[V2,27/28] PCI: tegra: Add support for GPIO based PCIe reset

Add support for GPIO based PERST# instead of SFIO mode controlled by AFI.
GPIO number comes from per port PCIe device tree node.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
---
V2: Using standard "reset-gpio" property

 drivers/pci/controller/pci-tegra.c | 36 +++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 6 deletions(-)

On Tue, Apr 23, 2019 at 02:58:24PM +0530, Manikanta Maddireddy wrote:
> Add support for GPIO based PERST# instead of SFIO mode controlled by AFI.
> GPIO number comes from per port PCIe device tree node.
> 
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> ---
> V2: Using standard "reset-gpio" property
> 
>  drivers/pci/controller/pci-tegra.c | 36 +++++++++++++++++++++++++-----
>  1 file changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
> index 72d344858e25..09b3b3e847c5 100644
> --- a/drivers/pci/controller/pci-tegra.c
> +++ b/drivers/pci/controller/pci-tegra.c
> @@ -17,6 +17,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/delay.h>
>  #include <linux/export.h>
> +#include <linux/gpio.h>
>  #include <linux/interrupt.h>
>  #include <linux/iopoll.h>
>  #include <linux/irq.h>
> @@ -26,6 +27,7 @@
>  #include <linux/module.h>
>  #include <linux/msi.h>
>  #include <linux/of_address.h>
> +#include <linux/of_gpio.h>
>  #include <linux/of_pci.h>
>  #include <linux/of_platform.h>
>  #include <linux/pci.h>
> @@ -400,6 +402,8 @@ struct tegra_pcie_port {
>  	unsigned int lanes;
>  
>  	struct phy **phys;
> +
> +	int reset_gpio;

Please store the struct gpio_desc * here.

>  };
>  
>  struct tegra_pcie_bus {
> @@ -583,15 +587,23 @@ static void tegra_pcie_port_reset(struct tegra_pcie_port *port)
>  	unsigned long value;
>  
>  	/* pulse reset signal */
> -	value = afi_readl(port->pcie, ctrl);
> -	value &= ~AFI_PEX_CTRL_RST;
> -	afi_writel(port->pcie, value, ctrl);
> +	if (gpio_is_valid(port->reset_gpio)) {
> +		gpiod_set_value(gpio_to_desc(port->reset_gpio), 0);

Then there's no need for the conversion between the integer and the
descriptor.

> +	} else {
> +		value = afi_readl(port->pcie, ctrl);
> +		value &= ~AFI_PEX_CTRL_RST;
> +		afi_writel(port->pcie, value, ctrl);
> +	}
>  
>  	usleep_range(1000, 2000);
>  
> -	value = afi_readl(port->pcie, ctrl);
> -	value |= AFI_PEX_CTRL_RST;
> -	afi_writel(port->pcie, value, ctrl);
> +	if (gpio_is_valid(port->reset_gpio)) {
> +		gpiod_set_value(gpio_to_desc(port->reset_gpio), 1);
> +	} else {
> +		value = afi_readl(port->pcie, ctrl);
> +		value |= AFI_PEX_CTRL_RST;
> +		afi_writel(port->pcie, value, ctrl);
> +	}
>  }
>  
>  static void tegra_pcie_enable_rp_features(struct tegra_pcie_port *port)
> @@ -2299,6 +2311,18 @@ static int tegra_pcie_parse_dt(struct tegra_pcie *pcie)
>  		if (IS_ERR(rp->base))
>  			return PTR_ERR(rp->base);
>  
> +		rp->reset_gpio = of_get_named_gpio(port, "reset-gpio", 0);

You can use devm_gpiod_get_from_of_node() to achieve this. Also, that
function allows you to pass in flags, so you no longer need the below
extra step to configure the GPIO.

> +		if (gpio_is_valid(rp->reset_gpio)) {
> +			err = devm_gpio_request_one(dev, rp->reset_gpio,
> +						    GPIOF_OUT_INIT_LOW,
> +						    "pex_reset");

Perhaps we want to include the port in the label somehow?

> +			if (err < 0) {
> +				dev_err(dev, "failed to request reset-gpio: %d\n",

Something like the below would be more consistent with the rest of the
driver:

	"failed to request reset GPIO: %d\n"

Thierry

> +					err);
> +				return err;
> +			}
> +		}
> +
>  		list_add_tail(&rp->list, &pcie->ports);
>  	}
>  
> -- 
> 2.17.1
>