Date:   Thu, 30 Jan 2020 15:39:54 -0600
From:   Suman Anna <s-anna@...com>
To:     "Andrew F. Davis" <afd@...com>, Tero Kristo <t-kristo@...com>,
        <bjorn.andersson@...aro.org>, <ohad@...ery.com>,
        <linux-remoteproc@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <mathieu.poirier@...aro.org>,
        <linux-omap@...r.kernel.org>
Subject: Re: [PATCHv5 06/14] remoteproc/omap: Initialize and assign reserved
 memory node

On 1/30/20 3:19 PM, Andrew F. Davis wrote:
> On 1/30/20 3:39 PM, Suman Anna wrote:
>> On 1/30/20 2:22 PM, Andrew F. Davis wrote:
>>> On 1/30/20 2:55 PM, Suman Anna wrote:
>>>> On 1/30/20 1:42 PM, Tero Kristo wrote:
>>>>> On 30/01/2020 21:20, Andrew F. Davis wrote:
>>>>>> On 1/30/20 2:18 PM, Tero Kristo wrote:
>>>>>>> On 30/01/2020 20:11, Andrew F. Davis wrote:
>>>>>>>> On 1/16/20 8:53 AM, Tero Kristo wrote:
>>>>>>>>> From: Suman Anna <s-anna@...com>
>>>>>>>>>
>>>>>>>>> The reserved memory nodes are not assigned to platform devices by
>>>>>>>>> default in the driver core to avoid the lookup for every platform
>>>>>>>>> device and incur a penalty as the real users are expected to be
>>>>>>>>> only a few devices.
>>>>>>>>>
>>>>>>>>> OMAP remoteproc devices fall into the above category and the OMAP
>>>>>>>>> remoteproc driver _requires_ specific CMA pools to be assigned
>>>>>>>>> for each device at the moment to align on the location of the
>>>>>>>>> vrings and vring buffers in the RTOS-side firmware images. So,
>>>>>>>>
>>>>>>>>
>>>>>>>> Same comment as before, this is a firmware issue for only some
>>>>>>>> firmwares
>>>>>>>> that do not handle being assigned vring locations correctly and instead
>>>>>>>> hard-code them.
>>>>
>>>> As for this statement, this can do with some updating. Post 4.20,
>>>> because of the lazy allocation scheme used for carveouts including the
>>>> vrings, the resource tables now have to use FW_RSC_ADDR_ANY and will
>>>> have to wait for the vdev synchronization to happen.
>>>>
>>>>>>>
>>>>>>> I believe we discussed this topic in length in previous version but
>>>>>>> there was no conclusion on it.
>>>>>>>
>>>>>>> The commit desc might be a bit misleading, we are not actually forced to
>>>>>>> use specific CMA buffers, as we use IOMMU to map these to device
>>>>>>> addresses. For example IPU1/IPU2 use internally exact same memory
>>>>>>> addresses, iommu is used to map these to specific CMA buffer.
>>>>>>>
>>>>>>> CMA buffers are mostly used so that we get aligned large chunk of memory
>>>>>>> which can be mapped properly with the limited IOMMU OMAP family of chips
>>>>>>> have. Not sure if there is any sane way to get this done in any other
>>>>>>> manner.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> Why not use the default CMA area?
>>>>>
>>>>> I think using default CMA area getting the actual memory block is not
>>>>> guaranteed and might fail. There are other users for the memory, and it
>>>>> might get fragmented at the very late phase we are grabbing the memory
>>>>> (omap remoteproc driver probe time.) Some chunks we need are pretty large.
>>>>>
>>>>> I believe I could experiment with this a bit though and see, or Suman
>>>>> could maybe provide feedback why this was designed initially like this
>>>>> and why this would not be a good idea.
>>>>
>>>> I have given some explanation on this on v4 as well, but if it is not
>>>> clear, there are restrictions with using default CMA. Default CMA has
>>>> switched to be assigned from the top of the memory (higher addresses,
>>>> since 3.18 IIRC), and the MMUs on IPUs and DSPs can only address
>>>> 32-bits. So, we cannot blindly use the default CMA pool, and this will
>>>> definitely not work on boards > 2 GB RAM. And, if you want to add in any
>>>> firewall capability, then specific physical addresses becomes mandatory.
>>>>
>>>
>>>
>>> If you need 32bit range allocations then
>>> dma_set_mask(dev, DMA_BIT_MASK(32));
>>>
>>> I'm not saying don't have support for carveouts, just make them
>>> optional, keystone_remoteproc.c does this:
>>>
>>> if (of_reserved_mem_device_init(dev))
>>> 	dev_warn(dev, "device does not have specific CMA pool\n");
>>>
>>> There doesn't even needs to be a warning but that is up to you.
>>
>> It is not exactly an apples to apples comparison. K2s do not have MMUs,
>> and most of our firmware images on K2 are actually running out of the
>> DSP internal memory.
>>
> 
> 
> So again we circle back to it being a firmware issue, if K2 can get away
> without needing carveouts and it doesn't even have an MMU then certainly
> OMAP/DRA7x class devices can handle it even better given they *do* have
> an IOMMU. Unless someone is hard-coding the IOMMU configuration.. In
> which case we are still just hacking around the problem here with
> mandatory specific address memory carveouts.

Optional carveouts on OMAP remoteprocs can be an enhancement in the
future, but at the moment, we won't be able to run use-cases without
this. And I have already given some of the reasons for the same here and
on v4.

regards
Suman

> 
> Andrew
> 
> 
>> regards
>> Suman
>>
>>>
>>> Andrew
>>>
>>>
>>>> regards
>>>> Suman
>>>>
>>>>>
>>>>> -Tero
>>>>>
>>>>>>
>>>>>> Andrew
>>>>>>
>>>>>>
>>>>>>> -Tero
>>>>>>>
>>>>>>>>
>>>>>>>> This is not a requirement of the remote processor itself and so it
>>>>>>>> should not fail to probe if a specific memory carveout isn't given.
>>>>>>>>
>>>>>>>>
>>>>>>>>> use the of_reserved_mem_device_init/release() API appropriately
>>>>>>>>> to assign the corresponding reserved memory region to the OMAP
>>>>>>>>> remoteproc device. Note that only one region per device is
>>>>>>>>> allowed by the framework.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Suman Anna <s-anna@...com>
>>>>>>>>> Signed-off-by: Tero Kristo <t-kristo@...com>
>>>>>>>>> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>>>>>>>>> ---
>>>>>>>>> v5: no changes
>>>>>>>>>
>>>>>>>>>    drivers/remoteproc/omap_remoteproc.c | 12 +++++++++++-
>>>>>>>>>    1 file changed, 11 insertions(+), 1 deletion(-)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/remoteproc/omap_remoteproc.c
>>>>>>>>> b/drivers/remoteproc/omap_remoteproc.c
>>>>>>>>> index 0846839b2c97..194303b860b2 100644
>>>>>>>>> --- a/drivers/remoteproc/omap_remoteproc.c
>>>>>>>>> +++ b/drivers/remoteproc/omap_remoteproc.c
>>>>>>>>> @@ -17,6 +17,7 @@
>>>>>>>>>    #include <linux/module.h>
>>>>>>>>>    #include <linux/err.h>
>>>>>>>>>    #include <linux/of_device.h>
>>>>>>>>> +#include <linux/of_reserved_mem.h>
>>>>>>>>>    #include <linux/platform_device.h>
>>>>>>>>>    #include <linux/dma-mapping.h>
>>>>>>>>>    #include <linux/remoteproc.h>
>>>>>>>>> @@ -480,14 +481,22 @@ static int omap_rproc_probe(struct
>>>>>>>>> platform_device *pdev)
>>>>>>>>>        if (ret)
>>>>>>>>>            goto free_rproc;
>>>>>>>>>    +    ret = of_reserved_mem_device_init(&pdev->dev);
>>>>>>>>> +    if (ret) {
>>>>>>>>> +        dev_err(&pdev->dev, "device does not have specific CMA
>>>>>>>>> pool\n");
>>>>>>>>> +        goto free_rproc;
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>>        platform_set_drvdata(pdev, rproc);
>>>>>>>>>          ret = rproc_add(rproc);
>>>>>>>>>        if (ret)
>>>>>>>>> -        goto free_rproc;
>>>>>>>>> +        goto release_mem;
>>>>>>>>>          return 0;
>>>>>>>>>    +release_mem:
>>>>>>>>> +    of_reserved_mem_device_release(&pdev->dev);
>>>>>>>>>    free_rproc:
>>>>>>>>>        rproc_free(rproc);
>>>>>>>>>        return ret;
>>>>>>>>> @@ -499,6 +508,7 @@ static int omap_rproc_remove(struct
>>>>>>>>> platform_device *pdev)
>>>>>>>>>          rproc_del(rproc);
>>>>>>>>>        rproc_free(rproc);
>>>>>>>>> +    of_reserved_mem_device_release(&pdev->dev);
>>>>>>>>>          return 0;
>>>>>>>>>    }
>>>>>>>>>
>>>>>>>
>>>>>>> -- 
>>>>>
>>>>> -- 
>>>>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>>>>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>>>
>>

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