> -----Original Message-----
> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> Sent: Tuesday, November 26, 2024 4:56 PM
> To: Carlos Song <carlos.song@xxxxxxx>
> Cc: Frank Li <frank.li@xxxxxxx>; o.rempel@xxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; andi.shyti@xxxxxxxxxx; shawnguo@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; imx@xxxxxxxxxxxxxxx;
> linux-i2c@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: [EXT] Re: [PATCH v2] i2c: imx: support DMA defer probing
>
> On 26.11.2024 16:25:35, carlos.song@xxxxxxx wrote:
> > From: Carlos Song <carlos.song@xxxxxxx>
> >
> > Return -EPROBE_DEFER when dma_request_slave_channel() because DMA
> > driver have not ready yet.
> >
> > Move i2c_imx_dma_request() before registering I2C adapter to avoid
> > infinite loop of .probe() calls to the same driver, see "e8c220fac415
> > Revert "i2c: imx: improve the error handling in i2c_imx_dma_request()""
> > and "Documentation/driver-api/driver-model/driver.rst".
> >
> > Use CPU mode to avoid stuck registering i2c adapter when DMA resources
> > are unavailable.
> >
> > Signed-off-by: Carlos Song <carlos.song@xxxxxxx>
> > Signed-off-by: Clark Wang <xiaoning.wang@xxxxxxx>
> > ---
> > Change for V2:
> > - According to Frank's comments, wrap at 75 char and Simplify fix code
> > at i2c_imx_dma_request().
> > - Use strict patch check, fix alignment warning at
> > i2c_imx_dma_request()
> > ---
> > drivers/i2c/busses/i2c-imx.c | 21 +++++++++++++--------
> > 1 file changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx.c
> > b/drivers/i2c/busses/i2c-imx.c index 5ed4cb61e262..4e5633166a1e 100644
> > --- a/drivers/i2c/busses/i2c-imx.c
> > +++ b/drivers/i2c/busses/i2c-imx.c
> > @@ -397,17 +397,16 @@ static void i2c_imx_reset_regs(struct
> > imx_i2c_struct *i2c_imx) }
> >
> > /* Functions for DMA support */
> > -static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
> > - dma_addr_t phy_addr)
> > +static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
> > +dma_addr_t phy_addr)
> > {
> > struct imx_i2c_dma *dma;
> > struct dma_slave_config dma_sconfig;
> > - struct device *dev = &i2c_imx->adapter.dev;
> > + struct device *dev = i2c_imx->adapter.dev.parent;
> > int ret;
> >
> > dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
> > if (!dma)
> > - return;
> > + return -ENOMEM;
> >
> > dma->chan_tx = dma_request_chan(dev, "tx");
> > if (IS_ERR(dma->chan_tx)) {
> > @@ -452,7 +451,7 @@ static void i2c_imx_dma_request(struct
> imx_i2c_struct *i2c_imx,
> > dev_info(dev, "using %s (tx) and %s (rx) for DMA transfers\n",
> > dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
> >
> > - return;
> > + return 0;
> >
> > fail_rx:
> > dma_release_channel(dma->chan_rx);
> > @@ -460,6 +459,8 @@ static void i2c_imx_dma_request(struct
> imx_i2c_struct *i2c_imx,
> > dma_release_channel(dma->chan_tx);
> > fail_al:
> > devm_kfree(dev, dma);
> > +
> > + return ret;
> > }
> >
> > static void i2c_imx_dma_callback(void *arg) @@ -1803,6 +1804,13 @@
> > static int i2c_imx_probe(struct platform_device *pdev)
> > if (ret == -EPROBE_DEFER)
> > goto clk_notifier_unregister;
> >
> > + /* Init DMA config if supported */
> > + ret = i2c_imx_dma_request(i2c_imx, phy_addr);
> > + if (ret == -EPROBE_DEFER) {
> > + dev_err(&pdev->dev, "DMA not ready, go defer probe!\n");
> > + goto clk_notifier_unregister;
> > + }
>
> Don't spam the logs if the driver defers probing, it's not a error. And it looks
> strange to ignore all other errors here. Either add a comment here, something
> like "continue without DMA", or let the function return
> 0 in case the driver should continue and propagate the error if the caller should
> take care of it.
>
Hi,
Thank you for your suggestion! I agree with you.
I will change to this logic:
ret = i2c_imx_dma_request(i2c_imx, phy_addr);
if (ret) {
if (ret == -EPROBE_DEFER)
goto clk_notifier_unregister;
dev_info(&pdev->dev, "use pio mode\n");
}
Ret = 0 -----> enable DMA successfully -------> no print
Ret!=0 -----> defer probe ---------> no print and try again
Ret!=0 -----> fail to enable DMA ------> remind now is using pio mode
Do you think the logic is acceptable?
> Marc
>
> --
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