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Wed, 27 Mar 2019 14:30:52 +0000 Received: from AM6PR10MB2661.EURPRD10.PROD.OUTLOOK.COM ([fe80::a442:a35b:115a:ef14]) by AM6PR10MB2661.EURPRD10.PROD.OUTLOOK.COM ([fe80::a442:a35b:115a:ef14%2]) with mapi id 15.20.1750.014; Wed, 27 Mar 2019 14:30:52 +0000 From: Rasmus Villemoes To: Mark Brown , "linux-spi@vger.kernel.org" CC: "linux-kernel@vger.kernel.org" , Fabio Estevam , Rasmus Villemoes Subject: [RFC PATCH 4/4] spi: spi-fsl-spi: automatically adapt bits-per-word in cpu mode Thread-Topic: [RFC PATCH 4/4] spi: spi-fsl-spi: automatically adapt bits-per-word in cpu mode Thread-Index: AQHU5KmutKOAcVt2iECfNjtmXOx7lA== Date: Wed, 27 Mar 2019 14:30:52 +0000 Message-ID: <20190327143040.16013-5-rasmus.villemoes@prevas.dk> References: <20190327143040.16013-1-rasmus.villemoes@prevas.dk> In-Reply-To: <20190327143040.16013-1-rasmus.villemoes@prevas.dk> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: HE1PR0402CA0055.eurprd04.prod.outlook.com (2603:10a6:7:7c::44) To AM6PR10MB2661.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:20b:a5::31) authentication-results: spf=none (sender IP is ) smtp.mailfrom=Rasmus.Villemoes@prevas.se; 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received-spf: None (protection.outlook.com: prevas.se does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: ri7o7yBT+iVSxKbDma2ovoPY0K0PHJztcIbgbKzgvWPxgM3WimQ8DxfjBJoAFC5Ss0YT2RzkxZJq8hn8y+oQusHpwZNYkL8e/uBwNFccrAb9/4VZudkviWEI6tpWxRafKxht5eHG3ab66iW6cIUsuUAVDOWF7p9EKQ4j0jS8TQ2Yq+q/eiwjjkZ+zVH/St3eo/TZC5GfobxKiXoppcCKI6SZiDnX08k8UYwjev1qmAGo6ljkTIEG+/dnmeyYmZ7MavmRPCbkoN2NWQQ32Ec5ZAW9rYU9Bsw798h5sDOLnD2uuRmysW3E7r2wtHyxRFdIva9gvue1mawK/1sTXKTpvfk7jOpZ09Dz4TAX9HGgUMPjhXh4TfmTlzvEaLitJHezGA8jSKL4FPyC4pMi2X3D75FmaFjgE6f5c3DyRXYVFZo= MIME-Version: 1.0 X-OriginatorOrg: prevas.dk X-MS-Exchange-CrossTenant-Network-Message-Id: ceb9f35c-7e0a-4a34-adc4-08d6b2c0d0c0 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Mar 2019 14:30:52.8829 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: d350cf71-778d-4780-88f5-071a4cb1ed61 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR10MB1894 Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Taking one interrupt for every byte is rather slow. Since the controller is perfectly capable of transmitting 32 bits at a time, change t->bits_per-word to 32 when the length is divisible by 4 and large enough that the reduced number of interrupts easily compensates for the one or two extra fsl_spi_setup_transfer() calls this causes. Signed-off-by: Rasmus Villemoes --- drivers/spi/spi-fsl-spi.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c index e2b341943796..b36ac6aa3b1f 100644 --- a/drivers/spi/spi-fsl-spi.c +++ b/drivers/spi/spi-fsl-spi.c @@ -363,12 +363,28 @@ static int fsl_spi_bufs(struct spi_device *spi, struct spi_transfer *t, static int fsl_spi_do_one_msg(struct spi_master *master, struct spi_message *m) { + struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(master); struct spi_device *spi = m->spi; struct spi_transfer *t, *first; unsigned int cs_change; const int nsecs = 50; int status, last_bpw; + /* + * In CPU mode, optimize large byte transfers to use larger + * bits_per_word values to reduce number of interrupts taken. + */ + if (!(mpc8xxx_spi->flags & SPI_CPM_MODE)) { + list_for_each_entry(t, &m->transfers, transfer_list) { + if (t->len < 256 || t->bits_per_word != 8) + continue; + if ((t->len & 3) == 0) + t->bits_per_word = 32; + else if ((t->len & 1) == 0) + t->bits_per_word = 16; + } + } + /* Don't allow changes if CS is active */ cs_change = 1; list_for_each_entry(t, &m->transfers, transfer_list) {