Re: [PATCH v3 2/8] s390/cio: introduce DMA pools to cio

[Halil Pasic <pasic@linux.ibm.com>]

On Mon, 3 Jun 2019 14:09:02 +0200
Michael Mueller <mimu@linux.ibm.com> wrote:

> >> @@ -224,6 +226,8 @@ struct subchannel *css_alloc_subchannel(struct subchannel_id schid,
> >>   	INIT_WORK(&sch->todo_work, css_sch_todo);
> >>   	sch->dev.release = &css_subchannel_release;
> >>   	device_initialize(&sch->dev);  
> > 
> > It might be helpful to add a comment why you use 31 bit here...  
> 
> @Halil, please let me know what comment you prefere here...
> 

How about?

/*
 * The physical addresses of some the dma structures that
 * can belong  to a subchannel need to fit 31 bit width (examples ccw,).
 */


> >   
> >> +	sch->dev.coherent_dma_mask = DMA_BIT_MASK(31);
> >> +	sch->dev.dma_mask = &sch->dev.coherent_dma_mask;
> >>   	return sch;
> >>   
> >>   err:
> >> @@ -899,6 +903,8 @@ static int __init setup_css(int nr)
> >>   	dev_set_name(&css->device, "css%x", nr);
> >>   	css->device.groups = cssdev_attr_groups;
> >>   	css->device.release = channel_subsystem_release;  
> > 
> > ...and 64 bit here.  
> 
> and here.

/*
 * We currently allocate notifier bits with this (using css->device
 * as the device argument with the DMA API), and are fine with 64 bit
 * addresses.
 */

Regards,
Halil