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Date: Thu, 27 Feb 2014 21:39:35 +0100
From: Marek Vasut <marex@...x.de>
To: linux-arm-kernel@...ts.infradead.org
Cc: Yuan Yao <yao.yuan@...escale.com>, wsa@...-dreams.de,
mark.rutland@....com, shawn.guo@...aro.org,
linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
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 ...
[...]
> 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 !
[...]
> +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 ?
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 .
> +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.
> +}
> /** 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 .
> + 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...
Besides, full-duplex DMA operation is missing, please explain why.
THanks!
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