linux-kernel - Re: [PATCH 1/1] PCI: armada8k: add device reset to link-down handle

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Message-ID: <ZzMimiRUAV6ecx1s@shell.armlinux.org.uk>
Date: Tue, 12 Nov 2024 09:40:42 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jenishkumar Maheshbhai Patel <jpatel2@...vell.com>
Cc: lpieralisi@...nel.org, thomas.petazzoni@...tlin.com, kw@...ux.com,
	manivannan.sadhasivam@...aro.org, robh@...nel.org,
	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	salee@...vell.com, dingwei@...vell.com
Subject: Re: [PATCH 1/1] PCI: armada8k: add device reset to link-down handle

On Mon, Nov 11, 2024 at 11:03:10PM -0800, Jenishkumar Maheshbhai Patel wrote:
> diff --git a/drivers/pci/controller/dwc/pcie-armada8k.c b/drivers/pci/controller/dwc/pcie-armada8k.c
> index b1b48c2016f7..9a48ef60be51 100644
> --- a/drivers/pci/controller/dwc/pcie-armada8k.c
> +++ b/drivers/pci/controller/dwc/pcie-armada8k.c
> @@ -23,6 +23,7 @@
>  #include <linux/of_pci.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/regmap.h>
> +#include <linux/of_gpio.h>
>  
>  #include "pcie-designware.h"
>  
> @@ -37,6 +38,8 @@ struct armada8k_pcie {
>  	struct regmap *sysctrl_base;
>  	u32 mac_rest_bitmask;
>  	struct work_struct recover_link_work;
> +	enum of_gpio_flags flags;
> +	struct gpio_desc *reset_gpio;
>  };
>  
>  #define PCIE_VENDOR_REGS_OFFSET		0x8000
> @@ -238,9 +241,18 @@ static void armada8k_pcie_recover_link(struct work_struct *ws)
>  	}
>  	pci_lock_rescan_remove();
>  	pci_stop_and_remove_bus_device(root_port);
> +	/* Reset device if reset gpio is set */
> +	if (pcie->reset_gpio) {
> +		/* assert and then deassert the reset signal */
> +		gpiod_set_value_cansleep(pcie->reset_gpio, 0);
> +		msleep(100);
> +		gpiod_set_value_cansleep(pcie->reset_gpio,
> +					 (pcie->flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1);

This looks wrong. resets are normally active-low.
gpiod_set_value_cansleep() should be called with '1' to indicate active
state, and '0' to indicate de-active state. DT should specify whether
the signal is active high or active low.

> +	/* Config reset gpio for pcie if the reset connected to gpio */
> +	reset_gpio = of_get_named_gpio_flags(pdev->dev.of_node,
> +					     "reset-gpios", 0,
> +					     &pcie->flags);
> +	if (gpio_is_valid(reset_gpio))
> +		pcie->reset_gpio = gpio_to_desc(reset_gpio);
> +

Just use devm_fwnode_gpiod_get() here, which will also handle the
cleanup.

To see how this should be done, look at
drivers/pci/controller/pci-mvebu.c which gets the polarity settings
correct too, as mentioned above.

Lastly, as this patch is related to the breaking DT change, it
_should_ have been sent as a patch series (which means the same
Cc list on each patch) so that reviewers can see the full story
and comments on the other patches.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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