Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752192AbbKIFoU (ORCPT ); Mon, 9 Nov 2015 00:44:20 -0500 Received: from mailgw01.mediatek.com ([210.61.82.183]:38479 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751864AbbKIFoP (ORCPT ); Mon, 9 Nov 2015 00:44:15 -0500 X-Listener-Flag: 11101 From: Liguo Zhang To: Wolfram Sang CC: , Matthias Brugger , Eddie Huang , Xudong Chen , Sascha Hauer , , , , , Liguo Zhang Subject: [PATCH v2 1/2] i2c: mediatek: add i2c first write then read optimization Date: Mon, 9 Nov 2015 13:43:58 +0800 Message-ID: <1447047839-5223-2-git-send-email-liguo.zhang@mediatek.com> X-Mailer: git-send-email 1.8.1.1.dirty In-Reply-To: <1447047839-5223-1-git-send-email-liguo.zhang@mediatek.com> References: <1447047839-5223-1-git-send-email-liguo.zhang@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4298 Lines: 134 For platform with auto restart support, between every transfer, i2c controller will trigger an interrupt and SW need to handle it to start new transfer. When doing write-then-read transfer, instead of restart mechanism, using WRRD mode to have controller send both transfer in one request to reduce latency. Signed-off-by: Liguo Zhang Reviewed-by: Eddie Huang --- drivers/i2c/busses/i2c-mt65xx.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c index 9b86716..dc4aac6 100644 --- a/drivers/i2c/busses/i2c-mt65xx.c +++ b/drivers/i2c/busses/i2c-mt65xx.c @@ -132,6 +132,7 @@ struct mtk_i2c_compatible { unsigned char pmic_i2c: 1; unsigned char dcm: 1; unsigned char auto_restart: 1; + unsigned char aux_len_reg: 1; }; struct mtk_i2c { @@ -153,6 +154,7 @@ struct mtk_i2c { enum mtk_trans_op op; u16 timing_reg; u16 high_speed_reg; + unsigned char auto_restart; const struct mtk_i2c_compatible *dev_comp; }; @@ -178,6 +180,7 @@ static const struct mtk_i2c_compatible mt6577_compat = { .pmic_i2c = 0, .dcm = 1, .auto_restart = 0, + .aux_len_reg = 0, }; static const struct mtk_i2c_compatible mt6589_compat = { @@ -185,6 +188,7 @@ static const struct mtk_i2c_compatible mt6589_compat = { .pmic_i2c = 1, .dcm = 0, .auto_restart = 0, + .aux_len_reg = 0, }; static const struct mtk_i2c_compatible mt8173_compat = { @@ -192,6 +196,7 @@ static const struct mtk_i2c_compatible mt8173_compat = { .pmic_i2c = 0, .dcm = 1, .auto_restart = 1, + .aux_len_reg = 1, }; static const struct of_device_id mtk_i2c_of_match[] = { @@ -373,7 +378,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs, i2c->irq_stat = 0; - if (i2c->dev_comp->auto_restart) + if (i2c->auto_restart) restart_flag = I2C_RS_TRANSFER; reinit_completion(&i2c->msg_complete); @@ -411,8 +416,14 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs, /* Set transfer and transaction len */ if (i2c->op == I2C_MASTER_WRRD) { - writew(msgs->len | ((msgs + 1)->len) << 8, - i2c->base + OFFSET_TRANSFER_LEN); + if (i2c->dev_comp->aux_len_reg) { + writew(msgs->len, i2c->base + OFFSET_TRANSFER_LEN); + writew((msgs + 1)->len, i2c->base + + OFFSET_TRANSFER_LEN_AUX); + } else { + writew(msgs->len | ((msgs + 1)->len) << 8, + i2c->base + OFFSET_TRANSFER_LEN); + } writew(I2C_WRRD_TRANAC_VALUE, i2c->base + OFFSET_TRANSAC_LEN); } else { writew(msgs->len, i2c->base + OFFSET_TRANSFER_LEN); @@ -461,7 +472,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs, writel(I2C_DMA_START_EN, i2c->pdmabase + OFFSET_EN); - if (!i2c->dev_comp->auto_restart) { + if (!i2c->auto_restart) { start_reg = I2C_TRANSAC_START; } else { start_reg = I2C_TRANSAC_START | I2C_RS_MUL_TRIG; @@ -518,6 +529,16 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap, if (ret) return ret; + i2c->auto_restart = i2c->dev_comp->auto_restart; + + /* checking if we can skip restart and optimize using WRRD mode */ + if (i2c->auto_restart && num == 2) { + if (!(msgs[0].flags & I2C_M_RD) && (msgs[1].flags & I2C_M_RD) && + msgs[0].addr == msgs[1].addr) { + i2c->auto_restart = 0; + } + } + while (left_num--) { if (!msgs->buf) { dev_dbg(i2c->dev, "data buffer is NULL.\n"); @@ -530,7 +551,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap, else i2c->op = I2C_MASTER_WR; - if (!i2c->dev_comp->auto_restart) { + if (!i2c->auto_restart) { if (num > 1) { /* combined two messages into one transaction */ i2c->op = I2C_MASTER_WRRD; @@ -559,7 +580,7 @@ static irqreturn_t mtk_i2c_irq(int irqno, void *dev_id) u16 restart_flag = 0; u16 intr_stat; - if (i2c->dev_comp->auto_restart) + if (i2c->auto_restart) restart_flag = I2C_RS_TRANSFER; intr_stat = readw(i2c->base + OFFSET_INTR_STAT); -- 1.8.1.1.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/