On 26.11.2024 12:07:59, Carlos Song wrote:
>
>
> > -----Original Message-----
> > From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> > Sent: Tuesday, November 26, 2024 6:24 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 10:15:27, Carlos Song wrote:
> > > > > 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?
> >
> > Yes, the other option is to move the logic into i2c_imx_dma_request() and let it
> > return 0 in case of DMA or fallback to PIO, or an error in case of probe defer or a
> > fatal error.
> >
> > This way the probe function will look like this:
> >
> > ret = i2c_imx_dma_request(i2c_imx, phy_addr);
> > if (ret)
> > return dev_err_probe(&pdev->dev, ret, "Failed to setup
> > DMA\n");
> >
>
> Sorry, I have some different ideas...
> 1. DMA mode should be optional for i2c-imx, because i2c-imx can accept DMA mode not enabled, because it still can work in CPU mode.
ACK
> If we use return dev_err_probe(), we have to return error at i2c_imx_dma_request() for "some fatal error", it will cause i2c_adapter can not be registered, then kill i2c adapter register.
i2c_imx_dma_request should only return an error if PIO mode is not an
option.
> If we always return 0 at i2c_imx_dma_request(), dev_err_probe will not work forever. So from my point, if DMA is not working well, just output a log to remind now i2c is always
> working at CPU mode, we have no DMA, this is enough.
ACK
> 2. when really defer probe, return dev_err_probe will return defer probe directly, but we still need to goto clk_notifier_unregister branch to free irq, clk_notifier_unregister and disable runtime pm.
> So we still need more judgement at probe function to handle this.
Not quite "dev_err_probe()" will not defer probe directly, the return in
"return dev_err_probe();" does. This should work:
ret = i2c_imx_dma_request(i2c_imx, phy_addr);
if (ret) {
dev_err_probe(&pdev->dev, ret, "Failed to setup DMA\n");
goto clk_notifier_unregister;
}
> So I prefer this logic:
This also works, LGTM!
> 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");
> }
regards,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
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Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
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