Re: [PATCH] iommu: silence iommu group prints

[Laurentiu Tudor <laurentiu.tudor@nxp.com>]

On 04.03.2020 11:33, Russell King - ARM Linux admin wrote:
> On Wed, Mar 04, 2020 at 10:56:06AM +0200, Laurentiu Tudor wrote:
>>
>> On 04.03.2020 00:17, Russell King - ARM Linux admin wrote:
>>> On Tue, Mar 03, 2020 at 05:55:05PM +0200, Laurentiu Tudor wrote:
>>>>   From c98dc05cdd45ae923654f2427985bd28bcde4bb2 Mon Sep 17 00:00:00 2001
>>>> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>>>> Date: Thu, 13 Feb 2020 11:59:12 +0200
>>>> Subject: [PATCH 1/4] bus: fsl-mc: add custom .dma_configure implementation
>>>> Content-Type: text/plain; charset="us-ascii"
>>>>
>>>> The devices on this bus are not discovered by way of device tree
>>>> but by queries to the firmware. It makes little sense to trick the
>>>> generic of layer into thinking that these devices are of related so
>>>> that we can get our dma configuration. Instead of doing that, add
>>>> our custom dma configuration implementation.
>>>
>>> Firstly, applying this to v5.5 results in a build failure, due to a
>>> missing linux/iommu.h include.
>>>
>>> Secondly, this on its own appears to make the DPAA2 network interfaces
>>> completely disappear.  Looking in /sys/bus/fsl-mc/drivers/*, none of
>>> the DPAA2 drivers are bound to anything, and looking in
>>> /sys/bus/fsl-mc/devices/, there is:
>>>
>>> lrwxrwxrwx 1 root root 0 Mar  3 22:06 dprc.1 -> ../../../devices/platform/soc/80c000000.fsl-mc/dprc.1
>>>
>>> This is booting with u-boot, so using DT rather than ACPI.
>>>
>>>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>>>> ---
>>>>    drivers/bus/fsl-mc/fsl-mc-bus.c | 42 ++++++++++++++++++++++++++++++++-
>>>>    1 file changed, 41 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
>>>> index 36eb25f82c8e..3df015eedae4 100644
>>>> --- a/drivers/bus/fsl-mc/fsl-mc-bus.c
>>>> +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
>>>> @@ -132,11 +132,51 @@ static int fsl_mc_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
>>>>    static int fsl_mc_dma_configure(struct device *dev)
>>>>    {
>>>>    	struct device *dma_dev = dev;
>>>> +	struct iommu_fwspec *fwspec;
>>>> +	const struct iommu_ops *iommu_ops;
>>>> +	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
>>>> +	int ret;
>>>> +	u32 icid;
>>>> +
>>>> +	/* Skip DMA setup for devices that are not DMA masters */
>>>> +	if (dev->type == &fsl_mc_bus_dpmcp_type ||
>>>> +	    dev->type == &fsl_mc_bus_dpbp_type ||
>>>> +	    dev->type == &fsl_mc_bus_dpcon_type ||
>>>> +	    dev->type == &fsl_mc_bus_dpio_type)
>>>> +		return 0;
>>>>    	while (dev_is_fsl_mc(dma_dev))
>>>>    		dma_dev = dma_dev->parent;
>>>> -	return of_dma_configure(dev, dma_dev->of_node, 0);
>>>> +	fwspec = dev_iommu_fwspec_get(dma_dev);
>>>> +	if (!fwspec)
>>>> +		return -ENODEV;
>>>
>>> The problem appears to be here - fwspec is NULL for dprc.1.
>>
>> Ok, that's because the iommu config is missing from the DT node that's
>> exposing the MC firmware. I've attached a fresh set of patches that include
>> on top the missing config and a workaround that makes MC work over SMMU.
>> Also added the missing #include, thanks for pointing out.
>> Let me know how it goes.
> 
> Shouldn't patch 6 should be first in the series, so that patch 1 does
> not cause a regression and bisectability damage?
> 

Correct, width one comment: both 5 and 6 should go first. Once iommu-map 
is added in the device tree the workaround for MC with the 
arm-smmu.disable_bypass boot arg will no longer work.

---
Best Regards, Laurentiu
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