netdev - Re: [PATCH v2 net-next 00/12] Add tc-mqprio and tc-taprio support for preemptible traffic classes

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Date:   Mon, 20 Feb 2023 13:48:16 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Ferenc Fejes <fejes@....elte.hu>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Gerhard Engleder <gerhard@...leder-embedded.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Roger Quadros <rogerq@...nel.org>,
        Pranavi Somisetty <pranavi.somisetty@....com>,
        Harini Katakam <harini.katakam@....com>,
        linux-kernel@...r.kernel.org,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Wong Vee Khee <vee.khee.wong@...ux.intel.com>,
        Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
        Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: [PATCH v2 net-next 00/12] Add tc-mqprio and tc-taprio support
 for preemptible traffic classes

On Mon, Feb 20, 2023 at 12:15:57PM +0100, Ferenc Fejes wrote:
> LGTM.
> 
> Reviewed-by: Ferenc Fejes <fejes@....elte.hu>

Thanks a lot for the review!

Unfortunately I need to send a v3, because the C language apparently
doesn't like "default" switch cases with no code, and I need to make
this change (which surprises me, since the code did compile fine with
my gcc-arm-11.2-2022.02-x86_64-aarch64-none-linux-gnu toolchain):

diff --git a/drivers/net/ethernet/mscc/ocelot_mm.c b/drivers/net/ethernet/mscc/ocelot_mm.c
index 21d5656dfc70..f7766927bdd2 100644
--- a/drivers/net/ethernet/mscc/ocelot_mm.c
+++ b/drivers/net/ethernet/mscc/ocelot_mm.c
@@ -57,20 +57,16 @@ void ocelot_port_update_preemptible_tcs(struct ocelot *ocelot, int port)
 
 	lockdep_assert_held(&mm->lock);
 	
-	/* On NXP LS1028A, when using QSGMII, the port hangs if transmitting
-	 * preemptible frames at any other link speed than gigabit
+	/* Only commit preemptible TCs when MAC Merge is active.
+	 * On NXP LS1028A, when using QSGMII, the port hangs if transmitting
+	 * preemptible frames at any other link speed than gigabit, so avoid
+	 * preemption at lower speeds in this PHY mode.
 	 */
-	if (ocelot_port->phy_mode != PHY_INTERFACE_MODE_QSGMII ||
-	    ocelot_port->speed == SPEED_1000) {
-		/* Only commit preemptible TCs when MAC Merge is active */
-		switch (mm->verify_status) {
-		case ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED:
-		case ETHTOOL_MM_VERIFY_STATUS_DISABLED:
-			val = mm->preemptible_tcs;
-			break;
-		default:
-		}
-	}
+	if ((ocelot_port->phy_mode != PHY_INTERFACE_MODE_QSGMII ||
+	     ocelot_port->speed == SPEED_1000) &&
+	    (mm->verify_status == ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED ||
+	     mm->verify_status == ETHTOOL_MM_VERIFY_STATUS_DISABLED))
+		val = mm->preemptible_tcs;
 	
 	ocelot_rmw_rix(ocelot, QSYS_PREEMPTION_CFG_P_QUEUES(val),
 		       QSYS_PREEMPTION_CFG_P_QUEUES_M,

Besides, I'm also taking the opportunity to make one more change, and
really do a thorough job with the netlink extack: I will be passing it
down to the device driver in v3, via struct tc_mqprio_qopt_offload and
struct tc_taprio_qopt_offload.

I'll replicate your review tag for all patches from v2 that will be
present in an unchanged form in v3, ok?