Re: [PATCHv7 04/12] driver/core: populate devices in order for IOMMUs

[Grant Likely]

On Thu, 12 Dec 2013 09:57:05 +0200, Hiroshi Doyu <hdoyu@xxxxxxxxxx> wrote:
> IOMMU devices on the bus need to be poplulated first, then iommu
> master devices are done later.
> 
> With CONFIG_OF_IOMMU, "iommus=" DT binding would be used to identify
> whether a device can be an iommu msater or not. If a device can, we'll
> defer to populate that device till an iommu device is populated. Then,
> those deferred iommu master devices are populated and configured with
> help of the already populated iommu device.
> 
> Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> This is related to the following discussion:
>   [RFC PATCH] Documentation: devicetree: add description for generic bus properties
>   http://lists.infradead.org/pipermail/linux-arm-kernel/2013-November/215042.html
> 
> v6:
> Spinned off only driver core part from:
>   [PATCHv5 2/9] driver/core: populate devices in order for IOMMUs
> 
> v5:
> Use "iommus=" binding instread of arm,smmu's "#stream-id-cells".
> 
> v4:
> This is newly added, and the successor of the following RFC:
>   [RFC][PATCHv3+ 1/2] driver/core: Add of_iommu_attach()
>   http://lists.linuxfoundation.org/pipermail/iommu/2013-November/006914.html
> 
> Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx>
> ---
>  drivers/base/dd.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 0605176..0605f52 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -25,6 +25,7 @@
>  #include <linux/async.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/pinctrl/devinfo.h>
> +#include <linux/of_iommu.h>
>  
>  #include "base.h"
>  #include "power/power.h"
> @@ -273,6 +274,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>  
>  	dev->driver = drv;
>  
> +	ret = of_iommu_attach(dev);
> +	if (ret)
> +		goto probe_failed;
> +

As discussed before, I really don't think hooking in to dd.c is the
right thing to do here, and certainly not as a device tree specific
function. ACPI or PCI described devices may have the same constraints
and those won't have DT descriptions.

I don't think we've got a good solution yet for this problem. :-(

g.
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