Hi Marek, Thank you very much for your suggestion. > -----Original Message----- > From: Marek Vasut [mailto:marex@xxxxxxx] > Sent: Friday, February 28, 2014 4:40 AM > To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: Yuan Yao-B46683; wsa@xxxxxxxxxxxxx; mark.rutland@xxxxxxx; > shawn.guo@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux- > i2c@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/3] i2c: add DMA support for freescale i2c driver > > On Thursday, February 27, 2014 at 07:05:14 AM, Yuan Yao wrote: > > [...] > > > *****/ @@ -63,6 +68,9 @@ > > /* Default value */ > > #define IMX_I2C_BIT_RATE 100000 /* 100kHz */ > > > > +/* enable DMA if transfer size is bigger than this threshold */ > > +#define IMX_I2C_DMA_THRESHOLD 16 > > So what's the unit here , potatoes or beers or what ? I suppose it's > bytes , but please make it explicit in the comment ... > Yes it's bytes. I will make it explicit in the comment. > [...] > > > static const struct imx_i2c_hwdata imx1_i2c_hwdata = { @@ -193,6 > > +216,7 @@ static const struct imx_i2c_hwdata imx1_i2c_hwdata = { > > .ndivs = ARRAY_SIZE(imx_i2c_clk_div), > > .i2sr_clr_opcode = I2SR_CLR_OPCODE_W0C, > > .i2cr_ien_opcode = I2CR_IEN_OPCODE_1, > > + .has_dma_support = false, > > > > }; > > > > @@ -203,6 +227,7 @@ static const struct imx_i2c_hwdata imx21_i2c_hwdata > = > > { .ndivs = ARRAY_SIZE(imx_i2c_clk_div), > > .i2sr_clr_opcode = I2SR_CLR_OPCODE_W0C, > > .i2cr_ien_opcode = I2CR_IEN_OPCODE_1, > > + .has_dma_support = false, > > > > }; > > > > @@ -213,6 +238,7 @@ static struct imx_i2c_hwdata vf610_i2c_hwdata = { > > .ndivs = ARRAY_SIZE(vf610_i2c_clk_div), > > .i2sr_clr_opcode = I2SR_CLR_OPCODE_W1C, > > .i2cr_ien_opcode = I2CR_IEN_OPCODE_0, > > + .has_dma_support = true, > > So why exactly don't we have a DT prop for determining whether the > controller has DMA support ? > > What about the other controllers, do they not support DMA for some > specific reason? Please elaborate on that, thank you ! Sorry for my fault. I will modify it. > [...] > > > +static void i2c_imx_dma_tx_callback(void *arg) > [...] > > +static int i2c_imx_dma_tx(struct imx_i2c_struct *i2c_imx, struct > > +i2c_msg > > *msgs) +{ > [...] > > +static void i2c_imx_dma_rx_callback(void *arg) > [...] > > +static int i2c_imx_dma_rx(struct imx_i2c_struct *i2c_imx, struct > > +i2c_msg > > *msgs) +{ > [...] > > Looks like there's quite a bit of code duplication in the four functions > above, can you not unify them ? > Yes, There's looks like quite a bit of code duplication in the four functions above. I also hate quite a bit of code duplication. But there are many differences in fact. If unify them we should add many conditional statements and auxiliary variable. I think it's superfluous and will damage the readability. So, I am very confused. And if you think unify them will be better I will modify it. Thanks for your suggestion and looking forward to hearing from you. > Also, can the DMA not do full-duplex operation ? What I see here is just > half- duplex operations , one for RX and the other one for TX . > Yes, here have two dma channels, one for RX and the other one for TX. When we request the channel we should determine it for TX or RX. > > +static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) { > > + struct imx_i2c_dma *dma = i2c_imx->dma; > > + struct dma_chan *dma_chan; > > + > > + dma_chan = dma->chan_tx; > > + dma->chan_tx = NULL; > > + dma->buf_tx = 0; > > + dma->len_tx = 0; > > + dma_release_channel(dma_chan); > > + > > + dma_chan = dma->chan_rx; > > + dma->chan_tx = NULL; > > + dma->buf_rx = 0; > > + dma->len_rx = 0; > > + dma_release_channel(dma_chan); > > You must make _DEAD_ _SURE_ this function is not ever called while the > DMA is still active. In your case, I have a feeling that's not handled. > I think this function will not called while the DMA is still active because of the Linux synchronization mechanism - completion. I used it in the dma function. > > +} > > /** Functions for IMX I2C adapter driver > > *************************************** > > ********************************************************************** > > **** > > *****/ > > > > @@ -425,7 +600,8 @@ static irqreturn_t i2c_imx_isr(int irq, void > *dev_id) > > return IRQ_NONE; > > } > > > > -static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct > > i2c_msg > > *msgs) +static int i2c_imx_pio_write(struct imx_i2c_struct *i2c_imx, > > + struct i2c_msg *msgs) > > { > > int i, result; > > > > @@ -458,7 +634,56 @@ static int i2c_imx_write(struct imx_i2c_struct > > *i2c_imx, struct i2c_msg *msgs) return 0; } > > > > -static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct > > i2c_msg > > *msgs) +static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx, > > + struct i2c_msg *msgs) > > +{ > > + int result, timeout=1000; > > + unsigned int temp = 0; > > + > > + reinit_completion(&i2c_imx->dma->cmd_complete); > > + result = i2c_imx_dma_tx(i2c_imx, msgs); > > + if(result) > > + return result; > > + > > + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); > > + temp |= I2CR_DMAEN; > > + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); > > + > > + /* write slave address */ > > + imx_i2c_write_reg(msgs->addr << 1, i2c_imx, IMX_I2C_I2DR); > > + result = wait_for_completion_interruptible_timeout( > > + &i2c_imx->dma->cmd_complete, > > + msecs_to_jiffies(1000)); > > Pull the magic constant of 1000 out and #define it as some > I2C_IMX_DMA_TIMEOUT please . > Thanks, I will modify it. > > + if (result == 0) > > + return -ETIMEDOUT; > > + > > + /* waiting for Transfer complete. */ > > + while(timeout--) { > > + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR); > > + if (temp & 0x80) > > + break; > > + udelay(10); > > + } > > + > > + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); > > + temp &= ~I2CR_DMAEN; > > + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); > > + > > + /* write the last byte */ > > + imx_i2c_write_reg(msgs->buf[msgs->len-1], i2c_imx, IMX_I2C_I2DR); > > + result = i2c_imx_trx_complete(i2c_imx); > > + if (result) > > + return result; > > + > > + result = i2c_imx_acked(i2c_imx); > > + if (result) > > + return result; > > + > > + return 0; > > +} > > + > > +static int i2c_imx_pio_read(struct imx_i2c_struct *i2c_imx, > > + struct i2c_msg *msgs) > > { > > int i, result; > > unsigned int temp; > > @@ -518,6 +743,80 @@ static int i2c_imx_read(struct imx_i2c_struct > > *i2c_imx, struct i2c_msg *msgs) return 0; } > > > > +static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx, > > + struct i2c_msg *msgs) > > +{ > > Looks like almost an duplication as well... > Considering the symmetric with them i2c_imx_dma_write. i2c_imx_dma_write and i2c_imx_pio_write have many differences. So I separate them. But i2c_imx_dma_read and i2c_imx_pio_read is the same at first part. I may should unify them. But it's will not symmetric with them i2c_imx_dma_write if unified them. So I don't know which will be better? Looking forward to hearing from you. > Besides, full-duplex DMA operation is missing, please explain why. > > THanks! > ��.n��������+%������w��{.n�����{��-��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
