Re: [PATCH RESEND 1/7] tty: serial: 8250: omap: fix kernel crash in suspend-to-ram

[Peter Hurley <peter-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org>]

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?

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 <nsekhar-l0cyMroinI0@public.gmane.org>
> ---
> 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