Re: [PATCH v2 4/9] PCI: aardvark: issue PERST via GPIO

["Pali Rohár" <pali@kernel.org>]

On Thursday 23 April 2020 13:41:51 Bjorn Helgaas wrote:
> [+cc Rob]
> 
> On Tue, Apr 21, 2020 at 01:16:56PM +0200, Marek Behún wrote:
> > From: Pali Rohár <pali@kernel.org>
> > 
> > Add support for issuing PERST via GPIO specified in 'reset-gpios'
> > property (as described in PCI device tree bindings).
> > 
> > Some buggy cards (e.g. Compex WLE900VX or WLE1216) are not detected
> > after reboot when PERST is not issued during driver initialization.
> 
> Does this slot support hotplug?

I have no idea. I have not heard that anybody tried hotplugging cards
with this aardvark pcie controller at runtime.

This patch fixes initialization only at boot time when cards were
plugged prior powering board on.

> If so, I don't think this fix will help the hot-add case, will it?

I even do not know if aardvark HW supports it. And if yes, I think it is
unimplemented and/or broken.

In documentation there is some interrupt register which could signal it,
but I it is not used by kernel's pci-aardvark.c driver.

> > Tested on Turris MOX.
> > 
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > ---
> >  drivers/pci/controller/pci-aardvark.c | 32 +++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > index 606bae1e7a88..e2d18094d8ca 100644
> > --- a/drivers/pci/controller/pci-aardvark.c
> > +++ b/drivers/pci/controller/pci-aardvark.c
> > @@ -9,6 +9,7 @@
> >   */
> >  
> >  #include <linux/delay.h>
> > +#include <linux/gpio.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/irq.h>
> >  #include <linux/irqdomain.h>
> > @@ -18,6 +19,7 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/msi.h>
> >  #include <linux/of_address.h>
> > +#include <linux/of_gpio.h>
> >  #include <linux/of_pci.h>
> >  
> >  #include "../pci.h"
> > @@ -204,6 +206,7 @@ struct advk_pcie {
> >  	int root_bus_nr;
> >  	int link_gen;
> >  	struct pci_bridge_emul bridge;
> > +	struct gpio_desc *reset_gpio;
> >  };
> >  
> >  static inline void advk_writel(struct advk_pcie *pcie, u32 val, u64 reg)
> > @@ -329,10 +332,23 @@ static void advk_pcie_train_link(struct advk_pcie *pcie)
> >  	dev_err(dev, "link never came up\n");
> >  }
> >  
> > +static void advk_pcie_issue_perst(struct advk_pcie *pcie)
> > +{
> > +	if (!pcie->reset_gpio)
> > +		return;
> > +
> > +	dev_info(&pcie->pdev->dev, "issuing PERST via reset GPIO for 1ms\n");
> > +	gpiod_set_value_cansleep(pcie->reset_gpio, 1);
> > +	usleep_range(1000, 2000);
> > +	gpiod_set_value_cansleep(pcie->reset_gpio, 0);
> > +}
> > +
> >  static void advk_pcie_setup_hw(struct advk_pcie *pcie)
> >  {
> >  	u32 reg;
> >  
> > +	advk_pcie_issue_perst(pcie);
> > +
> >  	/* Set to Direct mode */
> >  	reg = advk_readl(pcie, CTRL_CONFIG_REG);
> >  	reg &= ~(CTRL_MODE_MASK << CTRL_MODE_SHIFT);
> > @@ -1045,6 +1061,22 @@ static int advk_pcie_probe(struct platform_device *pdev)
> >  	}
> >  	pcie->root_bus_nr = bus->start;
> >  
> > +	pcie->reset_gpio = devm_gpiod_get_from_of_node(dev, dev->of_node,
> > +						       "reset-gpios", 0,
> > +						       GPIOD_OUT_LOW,
> > +						       "pcie1-reset");
> > +	ret = PTR_ERR_OR_ZERO(pcie->reset_gpio);
> > +	if (ret) {
> > +		if (ret == -ENOENT) {
> > +			pcie->reset_gpio = NULL;
> > +		} else {
> > +			if (ret != -EPROBE_DEFER)
> > +				dev_err(dev, "Failed to get reset-gpio: %i\n",
> > +					ret);
> > +			return ret;
> > +		}
> > +	}
> > +
> >  	pcie->link_gen = of_pci_get_max_link_speed(dev->of_node);
> >  	if (pcie->link_gen < 1 || pcie->link_gen > 2)
> >  		pcie->link_gen = 2;
> > -- 
> > 2.24.1
> >