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SubjectRe: [RESEND] i2c: imx: defer probing on dma channel request
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On 25/03/2019 15:30, laurentiu.tudor@nxp.com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>
> If the dma controller is not yet probed, defer i2c probe.
> The error path in probe was slightly modified (no functional change)

There is a functional change for cases like:

> ret = pm_runtime_get_sync(&pdev->dev);
> if (ret < 0)
> goto rpm_disable;

...as rpm_disable will no longer fall through to the call of
clk_disable_unprepare().

> to avoid triggering this WARN_ON():
> "cg-pll0-div1 already disabled
> WARNING: CPU: 1 PID: 1 at drivers/clk/clk.c:828 clk_core_disable+0xa8/0xb0"

I'm also not sure how this WARN_ON was hit. i2c_imx_probe() calls
clk_prepare_enable() which should increment the reference count. So it
should always be possible to decrememt the enable_count. What am I missing?

> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
> ---
> 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 42fed40198a0..4e34b1572756 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -1111,7 +1111,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
> pdev->name, i2c_imx);
> if (ret) {
> dev_err(&pdev->dev, "can't claim irq %d\n", irq);
> - goto clk_disable;
> + clk_disable_unprepare(i2c_imx->clk);
> + return ret;
> }
>
> /* Init queue */
> @@ -1161,19 +1162,25 @@ static int i2c_imx_probe(struct platform_device *pdev)
> pm_runtime_mark_last_busy(&pdev->dev);
> pm_runtime_put_autosuspend(&pdev->dev);
>
> + /* Init DMA config if supported */
> + ret = i2c_imx_dma_request(i2c_imx, phy_addr);
> + if (ret) {
> + if (ret != -EPROBE_DEFER)
> + dev_info(&pdev->dev, "can't use DMA, using PIO instead.\n");
> + else
> + goto del_adapter;
> + }
> +

This can be simplified by reversing the condition:

if (ret) {
if (ret == -EPROBE_DEFER)
goto del_adapter;
dev_info();
}

or even:

if (ret == -EPROBE_DEFER)
goto del_adapter;
else if (ret)
dev_info();

> dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", irq);
> dev_dbg(&i2c_imx->adapter.dev, "device resources: %pR\n", res);
> dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n",
> i2c_imx->adapter.name);
>
> - /* Init DMA config if supported */
> - ret = i2c_imx_dma_request(i2c_imx, phy_addr);
> - if (ret < 0)
> - goto clk_notifier_unregister;
> -
> dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
> return 0; /* Return OK */
>
> +del_adapter:
> + i2c_del_adapter(&i2c_imx->adapter);

This looks like a separate fix (previously the call to
i2c_add_numbered_adapter() was not undone in case of later errors). It
worth spelling this out in the commit message.

Thanks,

Steve

> clk_notifier_unregister:
> clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
> rpm_disable:
> @@ -1182,8 +1189,6 @@ static int i2c_imx_probe(struct platform_device *pdev)
> pm_runtime_set_suspended(&pdev->dev);
> pm_runtime_dont_use_autosuspend(&pdev->dev);
>
> -clk_disable:
> - clk_disable_unprepare(i2c_imx->clk);
> return ret;
> }
>
>

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