Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Sanket Parmar <sparmar@cadence.com>
To:     Christoph Hellwig <hch@infradead.org>
CC:     "peter.chen@kernel.org" <peter.chen@kernel.org>,
        Pawel Laszczak <pawell@cadence.com>,
        "a-govindraju@ti.com" <a-govindraju@ti.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Rahul Kumar <kurahul@cadence.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "kishon@ti.com" <kishon@ti.com>
Subject: RE: [PATCH 2/2] usb: cdns3: Optimize DMA request buffer allocation
Thread-Topic: [PATCH 2/2] usb: cdns3: Optimize DMA request buffer allocation
Thread-Index: AQHXFKPlwE5egmmpm02b66W+ylYqvKp7Y7sAgAAIZFA=
Date:   Tue, 9 Mar 2021 10:18:43 +0000
Message-ID: <BY5PR07MB81197BAC5B801816D2B2566CB0929@BY5PR07MB8119.namprd07.prod.outlook.com>
References: <1615267180-9289-1-git-send-email-sparmar@cadence.com>
 <1615267180-9289-2-git-send-email-sparmar@cadence.com>
 <20210309092804.GA76839@infradead.org>
In-Reply-To: <20210309092804.GA76839@infradead.org>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 34997be2-dba8-4bc0-53f8-08d8e2e4b7fb
X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Mar 2021 10:18:43.9131
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: d36035c5-6ce6-4662-a3dc-e762e61ae4c9
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: jAOwzh9oRSaazxUHSZ40G4bZrMp8l1jsMbU1pmofle47dbwhw7VssQpEoxNTwF/gs2Ci723zoLsqrp9fUNsV3swnHbAX+L/hFNXdI719JUI=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR07MB6513
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761
 definitions=2021-03-09_09:2021-03-08,2021-03-09 signatures=0
X-Proofpoint-Spam-Details: rule=outbound_check_notspam policy=outbound_check score=1
 lowpriorityscore=0 mlxscore=1 suspectscore=0 spamscore=1 clxscore=1011
 adultscore=0 phishscore=0 malwarescore=0 bulkscore=0 priorityscore=1501
 impostorscore=0 mlxlogscore=223 classifier=spam adjust=0 reason=mlx
 scancount=1 engine=8.12.0-2009150000 definitions=main-2103090049
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> On Tue, Mar 09, 2021 at 06:19:40AM +0100, Sanket Parmar wrote:
> > dma_alloc_coherent() might fail on the platform with a small DMA region=
.
> >
> > To avoid such failure in cdns3_prepare_aligned_request_buf(),
> > dma_alloc_coherent() is replaced with kmalloc and dma_map API to
> > allocate aligned request buffer of dynamic length.
>=20
> dma_alloc_noncoherent is the proper API instead of using kmalloc, which
> can lead to unaddressable memory that might require bounce buffering.

cdns3 device required DMA coherent buffer to perform operations. So=20
dma_alloc_noncoherent will not help here.

Also all gadget classes(except g_ether) use kmalloc to allocated request bu=
ffer,
and device driver uses usb_gadget_map_request_by_dev to map the request
buffer. Similar approach is used to allocate aligned buffer.=20

Thanks,
Sanket