linux-kernel - Re: [PATCH v4 02/27] thunderbolt: No need to read UID of the root switch on resume

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Date:   Tue, 06 Jun 2017 16:07:56 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Amir Levy <amir.jer.levy@...el.com>,
        Andy Lutomirski <luto@...nel.org>, Mario.Limonciello@...l.com,
        Jared.Dominguez@...l.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 02/27] thunderbolt: No need to read UID of the root
 switch on resume

On Tue, 2017-06-06 at 15:24 +0300, Mika Westerberg wrote:
> The root switch is part of the host controller and cannot be
> physically
> removed, so there is no point of reading UID again on resume in order
> to
> check if the root switch is still the same.
> 

FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>


> Suggested-by: Andreas Noever <andreas.noever@...il.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Andreas Noever <andreas.noever@...il.com>
> ---
>  drivers/thunderbolt/switch.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/thunderbolt/switch.c
> b/drivers/thunderbolt/switch.c
> index c6f30b1695a9..81f5164a6364 100644
> --- a/drivers/thunderbolt/switch.c
> +++ b/drivers/thunderbolt/switch.c
> @@ -452,19 +452,26 @@ void tb_sw_set_unplugged(struct tb_switch *sw)
>  int tb_switch_resume(struct tb_switch *sw)
>  {
>  	int i, err;
> -	u64 uid;
>  	tb_sw_info(sw, "resuming switch\n");
>  
> -	err = tb_drom_read_uid_only(sw, &uid);
> -	if (err) {
> -		tb_sw_warn(sw, "uid read failed\n");
> -		return err;
> -	}
> -	if (sw != sw->tb->root_switch && sw->uid != uid) {
> -		tb_sw_info(sw,
> -			"changed while suspended (uid %#llx ->
> %#llx)\n",
> -			sw->uid, uid);
> -		return -ENODEV;
> +	/*
> +	 * Check for UID of the connected switches except for root
> +	 * switch which we assume cannot be removed.
> +	 */
> +	if (tb_route(sw)) {
> +		u64 uid;
> +
> +		err = tb_drom_read_uid_only(sw, &uid);
> +		if (err) {
> +			tb_sw_warn(sw, "uid read failed\n");
> +			return err;
> +		}
> +		if (sw->uid != uid) {
> +			tb_sw_info(sw,
> +				"changed while suspended (uid %#llx
> -> %#llx)\n",
> +				sw->uid, uid);
> +			return -ENODEV;
> +		}
>  	}
>  
>  	/* upload configuration */

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy