linux-kernel - Re: [PATCH v2 7/9] driver core: Set fw

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Message-ID: <20220622074756.GA1647@pengutronix.de>
Date:   Wed, 22 Jun 2022 09:47:56 +0200
From:   Sascha Hauer <sha@...gutronix.de>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-gpio@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v2 7/9] driver core: Set fw_devlink.strict=1 by default

On Wed, Jun 01, 2022 at 12:07:03AM -0700, Saravana Kannan wrote:
> Now that deferred_probe_timeout is non-zero by default, fw_devlink will
> never permanently block the probing of devices. It'll try its best to
> probe the devices in the right order and then finally let devices probe
> even if their suppliers don't have any drivers.
> 
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

As mentioned here:

https://lore.kernel.org/lkml/20220622062027.994614-1-peng.fan@oss.nxp.com/

This patch has the effect that console UART devices which have "dmas"
properties specified in the device tree get deferred for 10 to 20
seconds. This happens on i.MX and likely on other SoCs as well. On i.MX
the dma channel is only requested at UART startup time and not at probe
time. dma is not used for the console. Nevertheless with this driver probe
defers until the dma engine driver is available.

It shouldn't go in as-is.

Sascha

> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 61fdfe99b348..977b379a495b 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1613,7 +1613,7 @@ static int __init fw_devlink_setup(char *arg)
>  }
>  early_param("fw_devlink", fw_devlink_setup);
>  
> -static bool fw_devlink_strict;
> +static bool fw_devlink_strict = true;
>  static int __init fw_devlink_strict_setup(char *arg)
>  {
>  	return strtobool(arg, &fw_devlink_strict);
> -- 
> 2.36.1.255.ge46751e96f-goog
> 
> 

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