Re: [PATCH 17/18] PCI: aardvark: Run link training in separate worker

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Sun, Feb 20, 2022 at 08:33:45PM +0100, Marek Behún wrote:
> From: Pali Rohár <pali@kernel.org>
> 
> Link training and PCIe card reset routines in Aardvark contain several
> delays, resulting in rather slow PCIe card probing. The worst case is
> when there is no card connected: the driver tries link training at all
> possible speeds and waits until all timers expire.
> 
> Since probe methods for all system devices are called sequentially, this
> results in noticeably longer boot time.
> 
> Move card reset and link training code from driver probe function into
> a separate worker, so that kernel can do something different while the
> driver is waiting during reset or training.
> 
> On ESPRESSObin and Turris MOX this decreases boot time by 0.4s with
> plugged PCIe card and by 2.2s if no card is connected.

I believe this is what the PROBE_PREFER_ASYNCHRONOUS flag in
struct device_driver.probe_type flag is there for unless I am
missing something obvious here.

Can you give it a try and report back please ?

Thanks,
Lorenzo

> Signed-off-by: Pali Rohár <pali@kernel.org>
> Signed-off-by: Marek Behún <kabel@kernel.org>
> ---
>  drivers/pci/controller/pci-aardvark.c | 42 ++++++++++++++++++---------
>  1 file changed, 28 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 8c9ac7766ac7..056f49d0e3a4 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -26,6 +26,7 @@
>  #include <linux/of_gpio.h>
>  #include <linux/of_pci.h>
>  #include <linux/timer.h>
> +#include <linux/workqueue.h>
>  
>  #include "../pci.h"
>  #include "../pci-bridge-emul.h"
> @@ -296,6 +297,8 @@ struct advk_pcie {
>  	int link_gen;
>  	bool link_was_up;
>  	struct timer_list link_irq_timer;
> +	struct delayed_work probe_card_work;
> +	bool host_bridge_probed;
>  	struct pci_bridge_emul bridge;
>  	struct gpio_desc *reset_gpio;
>  	struct clk *clk;
> @@ -497,6 +500,21 @@ static void advk_pcie_train_link(struct advk_pcie *pcie)
>  		dev_err(dev, "link never came up\n");
>  }
>  
> +static void advk_pcie_probe_card_work(struct work_struct *work)
> +{
> +	struct delayed_work *dwork = container_of(work, struct delayed_work,
> +						  work);
> +	struct advk_pcie *pcie = container_of(dwork, struct advk_pcie,
> +					      probe_card_work);
> +	struct pci_host_bridge *bridge = pci_host_bridge_from_priv(pcie);
> +	int ret;
> +
> +	advk_pcie_train_link(pcie);
> +	ret = pci_host_probe(bridge);
> +	if (!ret)
> +		pcie->host_bridge_probed = true;
> +}
> +
>  /*
>   * Set PCIe address window register which could be used for memory
>   * mapping.
> @@ -701,8 +719,6 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>  	/* Disable remaining PCIe outbound windows */
>  	for (i = pcie->wins_count; i < OB_WIN_COUNT; i++)
>  		advk_pcie_disable_ob_win(pcie, i);
> -
> -	advk_pcie_train_link(pcie);
>  }
>  
>  static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u32 *val)
> @@ -2112,14 +2128,8 @@ static int advk_pcie_probe(struct platform_device *pdev)
>  	bridge->ops = &advk_pcie_ops;
>  	bridge->map_irq = advk_pcie_map_irq;
>  
> -	ret = pci_host_probe(bridge);
> -	if (ret < 0) {
> -		irq_set_chained_handler_and_data(pcie->irq, NULL, NULL);
> -		advk_pcie_remove_rp_irq_domain(pcie);
> -		advk_pcie_remove_msi_irq_domain(pcie);
> -		advk_pcie_remove_irq_domain(pcie);
> -		return ret;
> -	}
> +	INIT_DELAYED_WORK(&pcie->probe_card_work, advk_pcie_probe_card_work);
> +	schedule_delayed_work(&pcie->probe_card_work, 1);
>  
>  	return 0;
>  }
> @@ -2131,11 +2141,15 @@ static int advk_pcie_remove(struct platform_device *pdev)
>  	u32 val;
>  	int i;
>  
> +	cancel_delayed_work_sync(&pcie->probe_card_work);
> +
>  	/* Remove PCI bus with all devices */
> -	pci_lock_rescan_remove();
> -	pci_stop_root_bus(bridge->bus);
> -	pci_remove_root_bus(bridge->bus);
> -	pci_unlock_rescan_remove();
> +	if (pcie->host_bridge_probed) {
> +		pci_lock_rescan_remove();
> +		pci_stop_root_bus(bridge->bus);
> +		pci_remove_root_bus(bridge->bus);
> +		pci_unlock_rescan_remove();
> +	}
>  
>  	/* Disable Root Bridge I/O space, memory space and bus mastering */
>  	val = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
> -- 
> 2.34.1
>