From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sekhar Nori Subject: Re: [PATCH RESEND 1/7] tty: serial: 8250: omap: fix kernel crash in suspend-to-ram Date: Thu, 9 Jul 2015 16:45:14 +0530 Message-ID: <559E57C2.5080009@ti.com> References: <559D2DFC.9010602@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <559D2DFC.9010602-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Hurley , Greg Kroah-Hartman , Tony Lindgren Cc: Linux OMAP Mailing List , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Device Tree Mailing List , John Ogness , Sebastian Andrzej Siewior , linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Kevin Hilman List-Id: devicetree@vger.kernel.org Hi Peter, On Wednesday 08 July 2015 07:34 PM, Peter Hurley wrote: > Hi Sekhar, > > On 07/06/2015 05:47 AM, Sekhar Nori wrote: >> omap_device infrastructure has a suspend_noirq hook which >> runtime suspends all devices late in the suspend cycle (see >> _od_suspend_noirq() in arch/arm/mach-omap2/omap_device.c) > > Why is omap2 the only arch/SoC that does this; ie., call the runtime > callbacks after the system pm callbacks? Even I am not sure why this needs to be done. I _think_ it was done to make sure all IPs are idled even if driver did not implement system sleep ops, but I could be wrong. Cc: Kevin Hilman since he added this support. In any case, I think this patch is okay, as the additional NULL pointer check is still valid. Thanks, Sekhar > > Whatever positive it brings, it's a mess at the driver level. > For example, this driver has to hook prepare()/complete() so it can > set local state so that it can detect when the runtime suspend > is being called during system suspend. > > Regards, > Peter Hurley > > >> This leads to a NULL pointer exception in 8250_omap driver >> since by the time omap8250_runtime_suspend() is called, 8250_dma >> driver has already set rxchan to NULL via serial8250_release_dma(). >> >> Make an explicit check to see if rxchan is NULL in >> runtime_{suspend|resume} hooks to fix this. >> >> Signed-off-by: Sekhar Nori >> --- >> Previous version: http://www.spinics.net/lists/linux-omap/msg119459.html >> No change in this version except rebased to v4.2-rc1 >> >> drivers/tty/serial/8250/8250_omap.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c >> index d75a66c72750..20c5b9c4c288 100644 >> --- a/drivers/tty/serial/8250/8250_omap.c >> +++ b/drivers/tty/serial/8250/8250_omap.c >> @@ -1285,7 +1285,7 @@ static int omap8250_runtime_suspend(struct device *dev) >> return -EBUSY; >> } >> >> - if (up->dma) >> + if (up->dma && up->dma->rxchan) >> omap_8250_rx_dma(up, UART_IIR_RX_TIMEOUT); >> >> priv->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE; >> @@ -1310,7 +1310,7 @@ static int omap8250_runtime_resume(struct device *dev) >> if (loss_cntx) >> omap8250_restore_regs(up); >> >> - if (up->dma) >> + if (up->dma && up->dma->rxchan) >> omap_8250_rx_dma(up, 0); >> >> priv->latency = priv->calc_latency; >> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html