linux-kernel - RE: [PATCH 13/13] rapidio/switches: add driver for IDT gen3 switches

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Date:	Thu, 21 Jul 2016 18:48:17 +0000
From:	"Bounine, Alexandre" <Alexandre.Bounine@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Matt Porter <mporter@...nel.crashing.org>,
	Andre van Herk <andre.van.herk@...drive-technologies.com>,
	"Wood, Barry" <Barry.Wood@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 13/13] rapidio/switches: add driver for IDT gen3 switches

> -----Original Message-----
> From: Andrew Morton [mailto:akpm@...ux-foundation.org]
> Sent: Thursday, July 21, 2016 2:37 PM
> To: Bounine, Alexandre
> Cc: Matt Porter; Andre van Herk; Wood, Barry; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 13/13] rapidio/switches: add driver for IDT gen3
> switches
> 
> On Thu, 21 Jul 2016 14:18:54 -0400 Alexandre Bounine
> <alexandre.bounine@....com> wrote:
> 
> > Add RapidIO switch driver for IDT Gen3 switch devices: RXS1632 and
> RXS2448.
> >
> > ...
> >
> > +static int
> > +idtg3_em_handler(struct rio_dev *rdev, u8 pnum)
> > +{
> > +	u32 err_status;
> > +	u32 rval;
> > +
> > +	rio_read_config_32(rdev,
> > +			RIO_DEV_PORT_N_ERR_STS_CSR(rdev, pnum),
> > +			&err_status);
> > +
> > +	/* Do nothing for device/link removal */
> > +	if (err_status & RIO_PORT_N_ERR_STS_PORT_UNINIT)
> > +		return 0;
> > +
> > +	/* When link is OK we have a device insertion.
> > +	 * Request port soft reset to clear errors if they present.
> > +	 * Inbound and outbound ackIDs will be 0 after reset.
> > +	 */
> > +	if (err_status & (RIO_PORT_N_ERR_STS_OUT_ES |
> > +				RIO_PORT_N_ERR_STS_INP_ES)) {
> > +		rio_read_config_32(rdev, RIO_PLM_SPx_IMP_SPEC_CTL(pnum),
> &rval);
> > +		rio_write_config_32(rdev, RIO_PLM_SPx_IMP_SPEC_CTL(pnum),
> > +				    rval | RIO_PLM_SPx_IMP_SPEC_CTL_SOFT_RST);
> > +		udelay(10);
> > +		rio_write_config_32(rdev, RIO_PLM_SPx_IMP_SPEC_CTL(pnum),
> rval);
> > +		mdelay(500);
> 
> Yikes, that's a very long busywait.  A half-second machine freeze on
> uniprocessor (if such exists ;)).  We can't use msleep()?
> 

My bad ;) No problem with msleep() at all. We just need to give enough time
for Rapidio link to get back (spec defines 500mS).
Do you want a patch on patch? 

> > +	}
> > +
> > +	return 0;
> > +}
> >
> > ...
> >