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Message-ID: <1e17ce716618472f9a0146c48f20b976@BL2PR03MB338.namprd03.prod.outlook.com>
Date: Wed, 26 Mar 2014 03:08:27 +0000
From: Yao Yuan <yao.yuan@...escale.com>
To: Marek Vasut <marex@...x.de>
CC: "wsa@...-dreams.de" <wsa@...-dreams.de>,
"mark.rutland@....com" <mark.rutland@....com>,
"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] i2c: add DMA support for freescale i2c driver
On Sunday, March 23, 2014 @ 11:50:00 AM, Marek Vasut wrote:
> On Thursday, March 13, 2014 at 02:47:56 AM, Yuan Yao wrote:
> > Add dma support for i2c. This function depend on DMA driver.
> > You can turn on it by write both the dmas and dma-name properties in
> > dts node.
> >
> > Signed-off-by: Yuan Yao <yao.yuan@...escale.com>
> > ---
> > drivers/i2c/busses/i2c-imx.c | 354
> > +++++++++++++++++++++++++++++++++++++------ 1 file changed, 306
> > insertions(+), 48 deletions(-)
>
> Changelog is missing.
Sorry for this, Maybe the changelog is in the junk box. It's named "[PATCH v3 0/2] i2c: add DMA support for freescale i2c driver".
> [...]
>
> > +/* Functions for DMA support */
> > +static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
> > + dma_addr_t phy_addr)
> > +{
> > + struct imx_i2c_dma *dma = i2c_imx->dma;
> > + struct dma_slave_config dma_sconfig;
> > + struct device *dev = &i2c_imx->adapter.dev;
> > + int ret;
> > +
> > + dma->chan_tx = dma_request_slave_channel(dev, "tx");
> > + if (!dma->chan_tx) {
> > + dev_err(dev, "Dma tx channel request failed!\n");
>
> DMA is written in all caps, it's an abbrev. for Direct Memory Access .
> Please fix globally.
>
Ok, I will fix it globally.
> [...]
>
> > static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct
> > i2c_msg
> > *msgs) {
>
> [...]
>
> > - /* write data */
> > - for (i = 0; i < msgs->len; i++) {
> > - dev_dbg(&i2c_imx->adapter.dev,
> > - "<%s> write byte: B%d=0x%X\n",
> > - __func__, i, msgs->buf[i]);
> > - imx_i2c_write_reg(msgs->buf[i], i2c_imx, IMX_I2C_I2DR);
> > + 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(IMX_I2C_DMA_TIMEOUT));
> > + if (result <= 0) {
> > + dmaengine_terminate_all(dma->chan_using);
> > + if (result)
> > + return result;
> > + else
> > + return -ETIMEDOUT;
> > + }
> > +
> > + /* waiting for Transfer complete. */
> > + while (timeout--) {
> > + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> > + if (temp & I2SR_ICF)
> > + break;
> > + udelay(10);
> > + }
>
> Do you ever check if this really timed out and handle such case at all ?
> I don't see it , but I might be wrong ...
>
Oh, It's a bug, Thank you very much.
> > + 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;
> > + } else {
> > + /* write slave address */
> > + imx_i2c_write_reg(msgs->addr << 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;
> > +
> > + dev_dbg(&i2c_imx->adapter.dev, "<%s> write data\n", __func__);
> > +
> > + /* write data */
> > + for (i = 0; i < msgs->len; i++) {
> > + dev_dbg(&i2c_imx->adapter.dev,
> > + "<%s> write byte: B%d=0x%X\n",
> > + __func__, i, msgs->buf[i]);
>
> Can you not just have a variable $dev here and avoid having such a long
> noodle in the dev_dbg() call ?
>
Ok, And I don't think the dev_dbg() is very helpful here now.
> > + imx_i2c_write_reg(msgs->buf[i], 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;
> > }
> [...]
>
> > + /* waiting for Transfer complete. */
> > + while (timeout--) {
> > + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> > + if (temp & I2SR_ICF)
> > + break;
> > + udelay(10);
> > + }
>
> Timeout handling here as well ...
>
> [...]
>
> > @@ -696,6 +936,21 @@ static int i2c_imx_probe(struct platform_device
> *pdev)
> > i2c_imx->adapter.name);
> > dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
> >
> > + /* Init DMA config if support*/
> > + i2c_imx->dma = devm_kzalloc(&pdev->dev, sizeof(struct imx_i2c_dma),
> > + GFP_KERNEL);
> > + if (!i2c_imx->dma) {
> > + dev_info(&pdev->dev,
> > + "can't allocate dma struct faild use dma.\n");
>
> Or just have $dev variable and you won't have to break the line at all ...
>
> > + i2c_imx->use_dma = false;
> > + } else if (i2c_imx_dma_request(i2c_imx, (dma_addr_t)phy_addr)) {
> > + dev_info(&pdev->dev,
> > + "can't request dma chan, faild use dma.\n");
> > + i2c_imx->use_dma = false;
> > + } else {
> > + i2c_imx->use_dma = true;
> > + }
>
> Can you not just check if i2c_imx->dma is valid pointer or NULL pointer ?
> Then you won't need a separate variable, for this purpose ... right ?
Sorry and I think what I know is just to check whether it is NULL.
Then for the second question, maybe there are some other ways, But I think it is more tidy and easier
understanding for using a separate variable, for this purpose.
> [...]
>
Best regards,
Yuan Yao
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