Re: [PATCH V6 26/27] PCI: tegra: Add support for GPIO based PERST#

From: Manikanta Maddireddy <mmaddireddy@nvidia.com>
To: Jon Hunter <jonathanh@nvidia.com>
Cc: thierry.reding@gmail.com, bhelgaas@google.com,
	robh+dt@kernel.org, mark.rutland@arm.com,
	lorenzo.pieralisi@arm.com, vidyas@nvidia.com,
	linux-tegra@vger.kernel.org, linux-pci@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH V6 26/27] PCI: tegra: Add support for GPIO based PERST#
Date: Thu, 4 Jul 2019 20:59:33 +0530	[thread overview]
Message-ID: <84d26bcc-f5d5-6694-98c9-1363d706d76c@nvidia.com> (raw)
In-Reply-To: <a4ddd0a3-f0b4-23de-fb0e-91a417d20362@nvidia.com>

On 04-Jul-19 8:18 PM, Jon Hunter wrote:
> On 18/06/2019 19:02, Manikanta Maddireddy wrote:
>> Tegra PCIe has fixed per port SFIO line to signal PERST#, which can be
>> controlled by AFI port register. However, if a platform routes a different
>> GPIO to the PCIe slot, then port register cannot control it. Add support
>> for GPIO based PERST# signal for such platforms. GPIO number comes from per
>> port PCIe device tree node. PCIe driver probe doesn't fail if per port
>> "reset-gpios" property is not populated, make sure that DT property is not
>> missed for such platforms.
> Really? So how come on Jetson TK1 I see ...
>
> [    1.073165] tegra-pcie 1003000.pcie: failed to get reset GPIO: -2
>
>
> [    1.073210] tegra-pcie: probe of 1003000.pcie failed with error -2
>
> And now ethernet is broken? Why has this not been tested on all Tegra
> platforms? There is no reason why code submitted to upstream by us
> (people at NVIDIA) have not tested this on our internal test farm. This
> is disappointing.

I did verified this patch on our internal TK1 test farm. I also tested
on TX1 and TX2.
This issue popped up because below fix in gpiolib driver went in
at the same time.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=025bf37725f1929542361eef2245df30badf242e

>> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
>> Acked-by: Thierry Reding <treding@nvidia.com>
>> ---
>> V6: No change
>>
>> V5:
>> * Updated reset gpio toggle logic to reflect active low usage
>> * Replaced kasprintf() with devm_kasprintf()
>> * Updated commit message with more information.
>>
>> V4: Using devm_gpiod_get_from_of_node() to get reset-gpios
>>
>> V3: Using helper function to get reset-gpios
>>
>> V2: Using standard "reset-gpio" property
>>
>>  drivers/pci/controller/pci-tegra.c | 45 ++++++++++++++++++++++++++----
>>  1 file changed, 39 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
>> index d2841532ff0e..a819bc087a05 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>
>> @@ -399,6 +400,8 @@ struct tegra_pcie_port {
>>  	unsigned int lanes;
>>  
>>  	struct phy **phys;
>> +
>> +	struct gpio_desc *reset_gpio;
>>  };
>>  
>>  struct tegra_pcie_bus {
>> @@ -544,15 +547,23 @@ 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 (port->reset_gpio) {
>> +		gpiod_set_value(port->reset_gpio, 1);
>> +	} 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 (port->reset_gpio) {
>> +		gpiod_set_value(port->reset_gpio, 0);
>> +	} 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)
>> @@ -2199,6 +2210,7 @@ static int tegra_pcie_parse_dt(struct tegra_pcie *pcie)
>>  		struct tegra_pcie_port *rp;
>>  		unsigned int index;
>>  		u32 value;
>> +		char *label;
>>  
>>  		err = of_pci_get_devfn(port);
>>  		if (err < 0) {
>> @@ -2257,6 +2269,27 @@ static int tegra_pcie_parse_dt(struct tegra_pcie *pcie)
>>  		if (IS_ERR(rp->base))
>>  			return PTR_ERR(rp->base);
>>  
>> +		label = devm_kasprintf(dev, GFP_KERNEL, "pex-reset-%u", index);
>> +		if (!label) {
>> +			dev_err(dev, "failed to create reset GPIO label\n");
>> +			return -ENOMEM;
>> +		}
>> +
>> +		/*
>> +		 * Returns null if reset-gpios property is not populated and
>> +		 * fall back to using AFI per port register to toggle PERST#
>> +		 * SFIO line.
>> +		 */
>> +		rp->reset_gpio = devm_gpiod_get_from_of_node(dev, port,
>> +							     "reset-gpios", 0,
>> +							     GPIOD_OUT_LOW,
>> +							     label);
>> +		if (IS_ERR(rp->reset_gpio)) {
>> +			err = PTR_ERR(rp->reset_gpio);
>> +			dev_err(dev, "failed to get reset GPIO: %d\n", err);
>> +			return err;
>> +		}
>> +
> So I believe that we can just remove the above. I will give it a test
> and see.
>
> Cheers
> Jon
>
Error check should be modified as follows,

	if (PTR_ERR(rp->reset_gpio) == -ENOENT)
		rp->reset_gpio = NULL;
	else if (IS_ERR(rp->reset_gpio))
 		return PTR_ERR(rp->reset_gpio);

Manikanta