| Message ID | 1447047839-5223-2-git-send-email-liguo.zhang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Nov 9, 2015 at 7:43 AM, Liguo Zhang <liguo.zhang@mediatek.com> wrote: > 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. > @@ -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) { Nitpick (optional): ((msgs[0].flags & msgs[1].flags) & I2C_M_RD) ? > + i2c->auto_restart = 0; > + } > + }
On Mon, Nov 9, 2015 at 10:25 PM, Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Mon, Nov 9, 2015 at 7:43 AM, Liguo Zhang <liguo.zhang@mediatek.com> wrote: >> 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. > > >> @@ -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) { > > Nitpick (optional): > > ((msgs[0].flags & msgs[1].flags) & I2C_M_RD) > ? IMHO, this makes the code less readable. Leave this to the compiler's optimizer. -Dan > >> + i2c->auto_restart = 0; >> + } >> + } > > -- > With Best Regards, > Andy Shevchenko > -- > 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/
On Mon, 2015-11-09 at 16:25 +0200, Andy Shevchenko wrote: > On Mon, Nov 9, 2015 at 7:43 AM, Liguo Zhang <liguo.zhang@mediatek.com> wrote: > > 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. > > > > @@ -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) { > > Nitpick (optional): > > ((msgs[0].flags & msgs[1].flags) & I2C_M_RD) > ? These 2 check for different conditions. The original one check the first one must NOT set I2C_M_RD, but second one must set I2C_M_RD. Joe.C
On Mon, Nov 09, 2015 at 01:43:58PM +0800, Liguo Zhang wrote: > 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 <liguo.zhang@mediatek.com> > Reviewed-by: Eddie Huang <eddie.huang@mediatek.com> Applied to for-next, thanks!
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);