linux-kernel - Re: [PATCH v2] i2c: imx: support DMA defer probing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID:
 <AM0PR0402MB39372380307BC4252BD131ACE82F2@AM0PR0402MB3937.eurprd04.prod.outlook.com>
Date: Tue, 26 Nov 2024 10:15:27 +0000
From: Carlos Song <carlos.song@....com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
CC: Frank Li <frank.li@....com>, "o.rempel@...gutronix.de"
	<o.rempel@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>,
	"andi.shyti@...nel.org" <andi.shyti@...nel.org>, "shawnguo@...nel.org"
	<shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "linux-i2c@...r.kernel.org"
	<linux-i2c@...r.kernel.org>, "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 v2] i2c: imx: support DMA defer probing



> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: Tuesday, November 26, 2024 4:56 PM
> To: Carlos Song <carlos.song@....com>
> Cc: Frank Li <frank.li@....com>; o.rempel@...gutronix.de;
> kernel@...gutronix.de; andi.shyti@...nel.org; shawnguo@...nel.org;
> s.hauer@...gutronix.de; festevam@...il.com; imx@...ts.linux.dev;
> linux-i2c@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH v2] i2c: imx: support DMA defer probing
> 
> On 26.11.2024 16:25:35, carlos.song@....com wrote:
> > From: Carlos Song <carlos.song@....com>
> >
> > 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@....com>
> > Signed-off-by: Clark Wang <xiaoning.wang@....com>
> > ---
> > 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
> 
> --
> Pengutronix e.K.                 | Marc Kleine-Budde          |
> Embedded Linux                   | https://www.pengutronix.de |
> Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |