linux-kernel - Re: [PATCHv5 06/14] remoteproc/omap: Initialize and assign reserved memory node

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Date:   Thu, 30 Jan 2020 21:18:52 +0200
From:   Tero Kristo <t-kristo@...com>
To:     "Andrew F. Davis" <afd@...com>, <bjorn.andersson@...aro.org>,
        <ohad@...ery.com>, <linux-remoteproc@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <mathieu.poirier@...aro.org>,
        <s-anna@...com>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCHv5 06/14] remoteproc/omap: Initialize and assign reserved
 memory node

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.

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.

-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;
>>   }
>>

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