Re: [PATCH v2 7/8] thunderbolt: Add support for Intel Ice Lake

From: Lukas Wunner <lukas@wunner.de>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: linux-kernel@vger.kernel.org,
	Andreas Noever <andreas.noever@gmail.com>,
	Michael Jamet <michael.jamet@intel.com>,
	Yehezkel Bernat <YehezkelShB@gmail.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <lenb@kernel.org>,
	Mario.Limonciello@dell.com,
	Anthony Wong <anthony.wong@canonical.com>,
	Rajmohan Mani <rajmohan.mani@intel.com>,
	Raanan Avargil <raanan.avargil@intel.com>,
	David Laight <David.Laight@ACULAB.COM>,
	linux-acpi@vger.kernel.org
Subject: Re: [PATCH v2 7/8] thunderbolt: Add support for Intel Ice Lake
Date: Tue, 13 Aug 2019 18:10:38 +0200	[thread overview]
Message-ID: <20190813161038.tip2u2z22xqnmfjl@wunner.de> (raw)
In-Reply-To: <20190812123847.50802-8-mika.westerberg@linux.intel.com>

On Mon, Aug 12, 2019 at 03:38:46PM +0300, Mika Westerberg wrote:
> +static void icm_veto_begin(struct tb *tb)
> +{
> +	struct icm *icm = tb_priv(tb);
> +
> +	if (!icm->veto) {
> +		icm->veto = true;
> +		/* Keep the domain powered while veto is in effect */
> +		pm_runtime_get(&tb->dev);
> +	}
> +}

Hm, don't you need memory barriers when accessing icm->veto?

If so, I'd suggest:

	/* Keep the domain powered while veto is in effect */
	if (cmpxchg(&icm->veto, false, true))
		pm_runtime_get(&tb->dev);

You'll have to declare icm->veto unsigned int instead of bool
because thunderbolt.ko is compiled if CONFIG_COMPILE_TEST is
enabled and there are arches which do not support cmpxchg for
a size of 1 byte.

The other bools in struct icm should likewise be unsigned int
per Linus' dictum:
https://lkml.org/lkml/2017/11/21/384

> --- a/drivers/thunderbolt/nhi.c
> +++ b/drivers/thunderbolt/nhi.c
> +/* Ice Lake specific NHI operations */
> +

Again, can't this be moved to a separate file for maintainability?

Thanks,

Lukas