linux-kernel - Re: [PATCH v4 3/4] PCI: pciehp: Add macros for hotplug operation delays

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Message-ID: <20251103153734.GA1806239@bhelgaas>
Date: Mon, 3 Nov 2025 09:37:34 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Hans Zhang <18255117159@....com>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v4 3/4] PCI: pciehp: Add macros for hotplug operation
 delays

[+cc Lukas]

On Sun, Nov 02, 2025 at 12:05:37AM +0800, Hans Zhang wrote:
> Add WAIT_PDS_TIMEOUT_MS and POLL_CMD_TIMEOUT_MS macros for hotplug
> operation delays to improve code readability.
> 
> Signed-off-by: Hans Zhang <18255117159@....com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index bcc51b26d03d..15b09c6a8d6b 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -28,6 +28,9 @@
>  #include "../pci.h"
>  #include "pciehp.h"
>  
> +#define WAIT_PDS_TIMEOUT_MS	10
> +#define POLL_CMD_TIMEOUT_MS	10
> +
>  static const struct dmi_system_id inband_presence_disabled_dmi_table[] = {
>  	/*
>  	 * Match all Dell systems, as some Dell systems have inband
> @@ -103,7 +106,7 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout)
>  			smp_mb();
>  			return 1;
>  		}
> -		msleep(10);
> +		msleep(POLL_CMD_TIMEOUT_MS);

Lukas might have different opinions and I would defer to him here.

But IMO (a) these aren't timeouts, they are poll intervals, (b) the
values are arbitrary with no connection to a spec, so less reason for
a #define, and (c) the #defines don't improve readability because now
I have to look at two places to understand the poll loops.

>  		timeout -= 10;
>  	} while (timeout >= 0);
>  	return 0;	/* timeout */
> @@ -283,7 +286,7 @@ static void pcie_wait_for_presence(struct pci_dev *pdev)
>  		pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
>  		if (slot_status & PCI_EXP_SLTSTA_PDS)
>  			return;
> -		msleep(10);
> +		msleep(WAIT_PDS_TIMEOUT_MS);
>  		timeout -= 10;
>  	} while (timeout > 0);
>  }
> -- 
> 2.34.1
>