Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) client-ip=23.128.96.38;
From:   Jianheng Zhang <Jianheng.Zhang@synopsys.com>
To:     Russell King <linux@armlinux.org.uk>,
        Serge Semin <fancer.lancer@gmail.com>
CC:     Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <Jose.Abreu@synopsys.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Tan Tee Min <tee.min.tan@intel.com>,
        Ong Boon Leong <boon.leong.ong@intel.com>,
        Voon Weifeng <weifeng.voon@intel.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-stm32@st-md-mailman.stormreply.com" 
        <linux-stm32@st-md-mailman.stormreply.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] net: stmmac: fix FPE events losing
Thread-Topic: [PATCH] net: stmmac: fix FPE events losing
Thread-Index: AdoW3Xfb3QHiuCaqTA2ROZ4444S4MgAFJ5GAADdg94AAAqmPIA==
Date:   Wed, 15 Nov 2023 16:00:42 +0000
Message-ID: <CY5PR12MB63727BAD92930CB04DE4DB52BFB1A@CY5PR12MB6372.namprd12.prod.outlook.com>
References: <CY5PR12MB6372857133451464780FD6B7BFB2A@CY5PR12MB6372.namprd12.prod.outlook.com>
 <xo4cbvc35zewabg4ite73trijy6fvbsaxsy6hag5qsr3dyharm@predjydxblsf>
 <ZVTU4TTFYSMLswTs@shell.armlinux.org.uk>
In-Reply-To: <ZVTU4TTFYSMLswTs@shell.armlinux.org.uk>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?E7VvxtUeALaCxIusTPcL0wSfWXpoZQ9zbGXcrvRLqIq3bvWXyr6Lej+RBs4g?=
 =?us-ascii?Q?mPv563ldab1qwJJGS1mk32j/cu0QPUBm4P5uAUdZGnoKZRFcVBEWUrg7fZ7E?=
 =?us-ascii?Q?L3t47M6LdRdQEeLL/jK91dAnOd4pv8sqyj6OlAkJaJ3eal/LyXhrsG6jXlA2?=
 =?us-ascii?Q?3V6JXU8W2ratCjKbbd9A42V3eoraiwSWpX0ZigUob6dMT+yRmz7G6KZbxTpg?=
 =?us-ascii?Q?5NpqcEB86PIBFR1R+9fCLdHlTwJTS95oMbo5OOtw7wECo2O1Mtvclz7Tw0vb?=
 =?us-ascii?Q?FSrG4vhhDeqPePNDBXLuInt0+goJLLi56vYYw4YhPGC0j91BPZqS7GBZorJm?=
 =?us-ascii?Q?u7onUGU484xGdHXYwzVREQ2xhyKmwHgj4vQ5xj73BwgXok6yIrVUHyKOT+p9?=
 =?us-ascii?Q?+EZSDT485jXJb/ryFq+l/XEXHwsMZaOrNEBOqTw3hCaYaPPUFpo2NE26begc?=
 =?us-ascii?Q?7E1/z3+R6IP0+ZzVs63G7X0t3OPvLWQTsodssE5N51zws84+6mx7D3ostOOj?=
 =?us-ascii?Q?mwHkiLnjJZtmPurE5FZllR8EMoPHx9DzlchpSPYpB697n8kYjS2hif2VpNJI?=
 =?us-ascii?Q?j/kwxW2F8RabNXPv/U3XJO71mxn1tv4Dq2veu8PRlT2/SbZASY3L+7yPtX0w?=
 =?us-ascii?Q?jO3IAGn2/iye72Q7pfcKjkdyFUijTUTdK2B5pzWQifaeldZSvTWOyZvqMhld?=
 =?us-ascii?Q?C9nRs8sWHpS5r+wYb6qCQHKP8G8Y57aflp4eB4zA/rJ7WVKgQULlVyviuZoe?=
 =?us-ascii?Q?eZSJX7wlL4ra4iDF1pV5R2Y4Sdgs+zshHFqTKCHQDpRT1Wqsq/k7x1pTFirV?=
 =?us-ascii?Q?woSKA7XE7aPwtV7LDRasZpDRUgiyTOW31SOwOx+J5CXbMJRIYmRXTcLH/7Dz?=
 =?us-ascii?Q?GEMXwKNXJR4lQgTYXWQ1P/+TFhklRGU98PpL111LZgFbHCvokucOeCzS4G/1?=
 =?us-ascii?Q?lrFvKN8CEtMm8JMRHoM8HJm47EhY6K8KIoZoBL5tzTihOK2A3m3PGhvQ3eBI?=
 =?us-ascii?Q?BFpG9bR3DbC0x0VkkhSVcJE90RlXAB8nEdObfZXk81CZPQy2Sfkv/oVj8DaQ?=
 =?us-ascii?Q?Ycw1Opp7mAwAEtjmLpLPW0QOGDtIz+gdKUdp7oMK+pNdkeA2YPFOjNSTANKX?=
 =?us-ascii?Q?geuZxi+W9JE00QmhuVIapwIjuUzMgynzIxae42yoXgTzuwQYwQMZHkhBI1aE?=
 =?us-ascii?Q?p+6kxf5nLPT+H1DfC50AhnkQXTbTfvieRTJAvkx+og17QjXhQbZ2qcu/K+11?=
 =?us-ascii?Q?MoDbvFatxQ0RbZzB0PS62QlvEblDAi94dMdypLl7trMXwxnsDXns6LuwE7lA?=
 =?us-ascii?Q?U2LMpHMRlf0x1nVj/XFJlSwTbHnAqz1ZJhW97/BoPKUN3vDMycIDUc3xRAtD?=
 =?us-ascii?Q?YYyP7dmEshvpRSP3r6YlHT2karz6KkIj/7YJSQCtG9y/SMxNUVQMn1SMa0qj?=
 =?us-ascii?Q?j41ECydlOwUlbcqaIhEqdIUgV0eR62x/LlliozE/D8VAjpeOsCSDNXiEgRwH?=
 =?us-ascii?Q?fLTVf0xGO7WlGq+RoOyf3017DiL2LdPSOhigScnbcYlpDu9+RyHEY1t7WzSE?=
 =?us-ascii?Q?dkjZX9rTOVKx2YgDuGUT0uKbxiDIlEAxmCu12Kgm?=
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?us-ascii?Q?TQODgumNoHHQpAxtiYY6l2LvCO5tVsQW13aAyS5ky6ciymMejTsKSWsnoIDm?=
 =?us-ascii?Q?1GvKPMYpxV90ov/c5GsPR6dQorPZcECFKaJTzo0KZuDugSvwnHu3siL1OdIY?=
 =?us-ascii?Q?ElcW4gbOWCFcHDUtJ8H7kcAxKoPJ6AjLoW0GZX4XcLvEZ06Ec4V9ep+zSbKQ?=
 =?us-ascii?Q?nGrFDy8maj1rC0ODcGKBZo3mZuBLIgOj00BHCuj0yTiE4dMjjMOf6qbmjF67?=
 =?us-ascii?Q?QijKlfSqwVa7ZpSamV5GmW+5zRVbJvC62h4w1RvFuIzbfp1uJZwU8f3yCrcE?=
 =?us-ascii?Q?IyVWtEXQ08dYjv1CkgxXq9rgZQlTYLGd/jdxdo1ejn1i6//Y/gt2rodaG/xt?=
 =?us-ascii?Q?rq4S9x6qQg+HOyx9QtDS+8KMNcr9PGCq5xMtDl0Mk/pSzRZ2p5W5aDYVx+aB?=
 =?us-ascii?Q?ao7Z1l8c8Pp3+s2Co2nX3NmostcP5TiuINQKKMFqnWhXKRDY8S4R3THJOtj/?=
 =?us-ascii?Q?hjbmIMl9VDTitoRslZmBSq3X8om42tTMng2md8OR53DSw94XXkRlMf94CXQI?=
 =?us-ascii?Q?15g1/PJ1kEHAutTnAgj1djZ8CnZeXPSpjjPbFvMdKouTCOsR784msyQxgPyG?=
 =?us-ascii?Q?8G24O5LiMaT1wFU6m9jbAdScsTKbnlbJPp3/vZEvv6Hdi6VSRlr9/+ndQlp1?=
 =?us-ascii?Q?21wcpq70I76rw+A4uEajADQrBK2q6l4PU6hMowPj1se4pQYgubf6+G8TbMoS?=
 =?us-ascii?Q?lXjM6HC8pTX/bP4TAYa91rvKkfbsbhYz3kgMskQ1ApjEauThrFs2CJ0EFmI9?=
 =?us-ascii?Q?FfBx44+LSO+yKSuScICa/ymWJuqV/ikBVD8xqUmNul9kKQzdCHssrtz4vDNa?=
 =?us-ascii?Q?f2ChOMNzq4so1/lB6t2aCW2DeNtDUdym2lk0NWqSHb2GjMYAS6viqFZbe1Mw?=
 =?us-ascii?Q?yLEU0lps5I+C/pJ2LKwv9ym+PXb94KE66wb2AWvxesn4LQvnkU1w4GZsE6h6?=
 =?us-ascii?Q?n3PbnfeT2GUtQEDdm8Q2UvHsJjCtK6s61pPqsZ5sGEV2NoWSI3US1IZY47Lo?=
 =?us-ascii?Q?wieRmiLiyQThEaF/kx6GzDVqiTz81XNBdHU0cm9RMqUIlZtZFUUUDqug9Rk1?=
 =?us-ascii?Q?GPZ10S6e/9Jur+/VFR89OkRA7dbBpXHvFCwdeH3xrB/pB1ctr0pfaXcvMPiX?=
 =?us-ascii?Q?Ih4xNZr04ahWLQjOb1eJhJp8iXZ44CNf1p/mqpNHNOawDrG6ZM/ILTyWcIeo?=
 =?us-ascii?Q?PxC/EeI7E2FTMtTe?=
X-OriginatorOrg: synopsys.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: CY5PR12MB6372.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 9adf4928-1b2f-40a0-e01d-08dbe5f40555
X-MS-Exchange-CrossTenant-originalarrivaltime: 15 Nov 2023 16:00:42.6799
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: c33c9f88-1eb7-4099-9700-16013fd9e8aa
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: ipTOJ/xVUyhdWax3on4FCuBqOp1WBgwcv1SiuvMMbK22KJI4xbm6UgccNvSMyBTsQA5pfIco6+x1ZYF/AiB7Vw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6299
X-Proofpoint-GUID: gwkuafP5yrBfNW-kGVJp3B-9IOvO4sp0
X-Proofpoint-ORIG-GUID: gwkuafP5yrBfNW-kGVJp3B-9IOvO4sp0
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2023-11-15_15,2023-11-15_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=outbound_active_cloned_notspam policy=outbound_active_cloned score=0
 mlxlogscore=999 lowpriorityscore=0 phishscore=0 spamscore=0 adultscore=0
 bulkscore=0 mlxscore=0 suspectscore=0 malwarescore=0 classifier=spam
 adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000
 definitions=main-2311150122
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Wed, 15 Nov 2023 08:02:02 -0800 (PST)


> -----Original Message-----
> From: Russell King <linux@armlinux.org.uk>
> Sent: Wednesday, November 15, 2023 10:26 PM
> To: Serge Semin <fancer.lancer@gmail.com>
> Cc: Jianheng Zhang <jianheng@synopsys.com>; Alexandre Torgue <alexandre.t=
orgue@foss.st.com>; Jose
> Abreu <joabreu@synopsys.com>; David S. Miller <davem@davemloft.net>; Eric=
 Dumazet
> <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pab=
eni@redhat.com>;
> Maxime Coquelin <mcoquelin.stm32@gmail.com>; Tan Tee Min <tee.min.tan@int=
el.com>; Ong Boon
> Leong <boon.leong.ong@intel.com>; Voon Weifeng <weifeng.voon@intel.com>; =
Mohammad Athari Bin
> Ismail <mohammad.athari.ismail@intel.com>; netdev@vger.kernel.org;
> linux-stm32@st-md-mailman.stormreply.com; linux-arm-kernel@lists.infradea=
d.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] net: stmmac: fix FPE events losing
>=20
> On Tue, Nov 14, 2023 at 02:59:57PM +0300, Serge Semin wrote:
> > On Tue, Nov 14, 2023 at 11:07:34AM +0000, Jianheng Zhang wrote:
> > > The 32-bit access of register MAC_FPE_CTRL_STS may clear the FPE stat=
us
> > > bits unexpectedly. Use 8-bit access for MAC_FPE_CTRL_STS control bits=
 to
> > > avoid unexpected access of MAC_FPE_CTRL_STS status bits that can redu=
ce
> > > the FPE handshake retries.
> > >
> > > The bit[19:17] of register MAC_FPE_CTRL_STS are status register bits.
> > > Those bits are clear on read (or write of 1 when RCWE bit in
> > > MAC_CSR_SW_Ctrl register is set). Using 32-bit access for
> > > MAC_FPE_CTRL_STS control bits makes side effects that clear the statu=
s
> > > bits. Then the stmmac interrupt handler missing FPE event status and
> > > leads to FPE handshake failure and retries.
> > >
> > > The bit[7:0] of register MAC_FPE_CTRL_STS are control bits or reserve=
d
> > > that have no access side effects, so can use 8-bit access for
> > > MAC_FPE_CTRL_STS control bits.
> > >
> > > Fixes: 5a5586112b92 ("net: stmmac: support FPE link partner hand-shak=
ing procedure")
> > > Signed-off-by: jianheng <jianheng@synopsys.com>
> > > ---
> > >  drivers/net/ethernet/stmicro/stmmac/dwmac5.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > index e95d35f..7333995 100644
> > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac5.c
> > > @@ -716,11 +716,11 @@ void dwmac5_fpe_configure(void __iomem *ioaddr,=
 u32 num_txq, u32
> num_rxq,
> > >  	u32 value;
> > >
> > >  	if (!enable) {
> >
> > > -		value =3D readl(ioaddr + MAC_FPE_CTRL_STS);
> > > +		value =3D readb(ioaddr + MAC_FPE_CTRL_STS);
> >
> > Note this may break the platforms which don't support non-32 MMIOs for
> > some devices. None of the currently supported glue-drivers explicitly
> > state they have such peculiarity, but at the same time the STMMAC-core
> > driver at the present state uses the dword IO ops only. For instance
> > the PCIe subsystem has the special accessors for such cases:
> > pci_generic_config_read32()
> > pci_generic_config_write32()
> > which at the very least are utilized on the Tegra and Loongson
> > platforms to access the host CSR spaces. These platforms are also
> > equipped with the DW MACs. The problem might be irrelevant for all the
> > currently supported DW MAC controllers implementations though, but
> > still it worth to draw an attention to the problem possibility and in
> > order to prevent it before ahead it would be better to just avoid
> > using the byte-/word- IOs if it's possible.
>=20
> Yes, this exists for configuration accesses, and is damn annoying
> because the read-modify-write of these can end up clearing PCI
> status register bits that are W1C.
>=20
> I've never heard of that problem with MMIO though.
>=20
> --
> RMK's Patch system:
> https://urldefense.com/v3/__https://www.armlinux.org.uk/developer/patches=
/__;!!A4F2R9G_pg!ZnsQc
> 7LKbdCiIj_nLBkt44MRSL8W8YD4WvMmPNkHFlDMrjrVqEVOVA1-P-9BVE3Oa5bC1ymKXLNV5C=
9mJ_rfFtLW
> Fg$
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
Thanks for all your mention about the potential risks of using readb and su=
ggestions, I'll consider a new solution and update the patch.

Best Regards,
Jianheng