linux-kernel - Re: [PATCH] i2c: stm32: remove unnecessary DMA kernel error log

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Message-ID: <20200910093019.GA1975@gnbcxd0016.gnb.st.com>
Date:   Thu, 10 Sep 2020 11:30:19 +0200
From:   Alain Volmat <alain.volmat@...com>
To:     Holger Assmann <h.assmann@...gutronix.de>
CC:     Pierre Yves MORDRET <pierre-yves.mordret@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Wolfram Sang <wsa@...nel.org>,
        Etienne CARRIERE <etienne.carriere@...com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: stm32: remove unnecessary DMA kernel error log

Hi Holger,

Thanks for your patch.
there is an ongoing tree wide action to update all those common pattern
of checking for the -EPROBE_DEFER.

I thus propose, to first integrate the patch [i2c: stm32: Simplify with dev_err_probe()] that has been proposed few days ago, and on top of that add an
additional patch to check for the -ENODEV error case due to DMA being
optional.

I've prepared a patch for that and will post it now, could you consider it ?

Alain

On Fri, Aug 14, 2020 at 02:13:55PM +0000, Holger Assmann wrote:
> We currently print errors twice when there is an actual error
> when requesting a DMA channel, once in stm32f7_i2c_probe()
> when stm32_i2c_dma_request() fails and once more in
> stm32_i2c_dma_request() itself. stm32_i2c_dma_request() is only
> called from stm32f7_i2c_probe(), so we could drop the duplicate
> error message.
> 
> This has the effect that we no longer warn about absence of a
> DMA channel. This is intended as it is not mandatory for the
> i2c-stm32 devices to have DMA enabled.  Also, the overall number
> of DMA channels on the STM32 is limited and has to be shared
> with other peripherals. This may lead to DMA being intentionally
> off for specific devices.
> 
> This patch removes the unnecessary error message.
> 
> Fixes: e07a89775c71 ("i2c: stm32: don't print an error on probe deferral")
> Signed-off-by: Holger Assmann <h.assmann@...gutronix.de>
> ---
>  drivers/i2c/busses/i2c-stm32.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32.c b/drivers/i2c/busses/i2c-stm32.c
> index 3f69a3bb6119..cc05a4202559 100644
> --- a/drivers/i2c/busses/i2c-stm32.c
> +++ b/drivers/i2c/busses/i2c-stm32.c
> @@ -26,8 +26,6 @@ struct stm32_i2c_dma *stm32_i2c_dma_request(struct device *dev,
>  	dma->chan_tx = dma_request_chan(dev, "tx");
>  	if (IS_ERR(dma->chan_tx)) {
>  		ret = PTR_ERR(dma->chan_tx);
> -		if (ret != -EPROBE_DEFER)
> -			dev_err(dev, "can't request DMA tx channel\n");
>  		goto fail_al;
>  	}
>  
> @@ -46,9 +44,6 @@ struct stm32_i2c_dma *stm32_i2c_dma_request(struct device *dev,
>  	dma->chan_rx = dma_request_chan(dev, "rx");
>  	if (IS_ERR(dma->chan_rx)) {
>  		ret = PTR_ERR(dma->chan_rx);
> -		if (ret != -EPROBE_DEFER)
> -			dev_err(dev, "can't request DMA rx channel\n");
> -
>  		goto fail_tx;
>  	}
>  
> -- 
> 2.20.1
>