Re: [PATCH v5 8/8] rpmsg: Turn name service into a stand alone driver

[Arnaud POULIQUEN <arnaud.pouliquen@st.com>]

On 11/12/20 12:51 PM, Guennadi Liakhovetski wrote:
> Hi Arnaud,
> 
> On Thu, Nov 12, 2020 at 11:17:54AM +0100, Arnaud POULIQUEN wrote:
>> Hi Guennadi,
>>
>> On 11/11/20 3:49 PM, Guennadi Liakhovetski wrote:
>>> Hi Arnaud,
> 
> [snip]
> 
>>> From: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
>>> Subject: [PATCH] fixup! rpmsg: Turn name service into a stand alone driver
>>>
>>> Link ns.c with core.c together to guarantee immediate probing.
>>>
>>> Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
>>> ---
>>>  drivers/rpmsg/Makefile                        |  2 +-
>>>  drivers/rpmsg/{rpmsg_core.c => core.c}        | 13 +++--
>>>  drivers/rpmsg/{rpmsg_ns.c => ns.c}            | 49 ++++++++++++++-----
>>>  drivers/rpmsg/virtio_rpmsg_bus.c              |  5 +-
>>>  include/linux/rpmsg.h                         |  4 +-
>>>  .../{rpmsg_byteorder.h => rpmsg/byteorder.h}  |  0
>>>  include/linux/{rpmsg_ns.h => rpmsg/ns.h}      | 16 +++---
>>>  7 files changed, 61 insertions(+), 28 deletions(-)
>>>  rename drivers/rpmsg/{rpmsg_core.c => core.c} (99%)
>>>  rename drivers/rpmsg/{rpmsg_ns.c => ns.c} (76%)
>>>  rename include/linux/{rpmsg_byteorder.h => rpmsg/byteorder.h} (100%)
>>>  rename include/linux/{rpmsg_ns.h => rpmsg/ns.h} (82%)
>>>
>>> diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
>>> index 8d452656f0ee..5aa79e167372 100644
>>> --- a/drivers/rpmsg/Makefile
>>> +++ b/drivers/rpmsg/Makefile
>>> @@ -1,7 +1,7 @@
>>>  # SPDX-License-Identifier: GPL-2.0
>>> +rpmsg_core-objs			:= core.o ns.o
>>>  obj-$(CONFIG_RPMSG)		+= rpmsg_core.o
>>>  obj-$(CONFIG_RPMSG_CHAR)	+= rpmsg_char.o
>>> -obj-$(CONFIG_RPMSG_NS)		+= rpmsg_ns.o
>>>  obj-$(CONFIG_RPMSG_MTK_SCP)	+= mtk_rpmsg.o
>>>  qcom_glink-objs			:= qcom_glink_native.o qcom_glink_ssr.o
>>>  obj-$(CONFIG_RPMSG_QCOM_GLINK) += qcom_glink.o
>>> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/core.c
>>> similarity index 99%
>>> rename from drivers/rpmsg/rpmsg_core.c
>>> rename to drivers/rpmsg/core.c
>>> index 6381c1e00741..0c622cced804 100644
>>> --- a/drivers/rpmsg/rpmsg_core.c
>>> +++ b/drivers/rpmsg/core.c
>>> @@ -14,6 +14,7 @@
>>>  #include <linux/kernel.h>
>>>  #include <linux/module.h>
>>>  #include <linux/rpmsg.h>
>>> +#include <linux/rpmsg/ns.h>
>>>  #include <linux/of_device.h>
>>>  #include <linux/pm_domain.h>
>>>  #include <linux/slab.h>
>>> @@ -625,21 +626,27 @@ void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv)
>>>  }
>>>  EXPORT_SYMBOL(unregister_rpmsg_driver);
>>>  
>>> -
>>>  static int __init rpmsg_init(void)
>>>  {
>>>  	int ret;
>>>  
>>>  	ret = bus_register(&rpmsg_bus);
>>> -	if (ret)
>>> +	if (ret) {
>>>  		pr_err("failed to register rpmsg bus: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = rpmsg_ns_init();
>>> +	if (ret)
>>> +		bus_unregister(&rpmsg_bus);
>>>  
>>>  	return ret;
>>>  }
>>>  postcore_initcall(rpmsg_init);
>>>  
>>> -static void __exit rpmsg_fini(void)
>>> +static void rpmsg_fini(void)
>>>  {
>>> +	rpmsg_ns_exit();
>>>  	bus_unregister(&rpmsg_bus);
>>>  }
>>>  module_exit(rpmsg_fini);
>>
>> The drawback of this solution is that it makes the anoucement service ns
>> mandatory, but it is optional because it depends on the RPMsg backend bus.
>> RPMsg NS should be generic but optional.
>> What about calling this in rpmsg_virtio?
> 
> This just registers a driver. If the backend doesn't register a suitable 
> device by calling rpmsg_ns_register_device(); nothing happens. But if 
> you're concerned about wasted memory, we can make it conditional on a 
> configuration option.
I'm not worried about memory, but I'm trying to understand why this can't be
done in the background rather than the kernel. Doing this in the kernel can be
confusing enough to backend such as GLINK bus that does not use this service.

I saw also this alternative to keep module independent, but i did not test it yet.

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_fb_helper.c#L2274

> 
>>> diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/ns.c
>>> similarity index 76%
>>> rename from drivers/rpmsg/rpmsg_ns.c
>>> rename to drivers/rpmsg/ns.c
>>> index 8e26824ca328..86c011bfb62f 100644
>>> --- a/drivers/rpmsg/rpmsg_ns.c
>>> +++ b/drivers/rpmsg/ns.c
>>> @@ -2,15 +2,47 @@
>>>  /*
>>>   * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
>>>   */
>>> +#include <linux/completion.h>
>>>  #include <linux/device.h>
>>> +#include <linux/export.h>
>>>  #include <linux/kernel.h>
>>>  #include <linux/module.h>
>>> -#include <linux/slab.h>
>>>  #include <linux/rpmsg.h>
>>> -#include <linux/rpmsg_ns.h>
>>> +#include <linux/rpmsg/ns.h>
>>> +#include <linux/slab.h>
>>>  
>>>  #include "rpmsg_internal.h"
>>>  
>>> +int rpmsg_ns_register_device(struct rpmsg_device *rpdev)
>>> +{
>>> +	int ret;
>>> +
>>> +	strcpy(rpdev->id.name, "rpmsg_ns");
>>> +	rpdev->driver_override = "rpmsg_ns";
>>> +	rpdev->src = RPMSG_NS_ADDR;
>>> +	rpdev->dst = RPMSG_NS_ADDR;
>>> +
>>> +	ret = rpmsg_register_device(rpdev);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	if (!wait_for_completion_timeout(&rpdev->ns_ready,
>>> +					 msecs_to_jiffies(1))) {
>>
>> Does this work if called in rproc_virtio_probe? i tried a similar implementation
>> but it always falls in timeout because rpmsg_ns_probe never called, probably due
>> to the serial probing.The rpmsg_ns probe always occurs after the end of the
>> virtio probe.
> 
> It works, yes. As you see, rpmsg_register_device() is called first, that can 
> already result in the .probe() being called and the completion being signalled
> before we actually start a wait on it. That works well. BTW, the version here is 
> missing a call to
> 
> +	init_completion(&rpdev->ns_ready);
> 
> right above the call to rpmsg_register_device(). But yes, it works.
> 
>> For me the wait completion can not be called during the virtio probe. That's why
>> i implemented it in rpmsg_recv_done to ensure that the service is available
>> before first message treatment.
> 
> Why can it not be called in rpmsg_ns_probe()? The only purpose of this completion 
> is to make sure that rpmsg_create_ept() for the NS endpoint has completed before 
> we begin communicating with the remote / host, e.g. by calling 
> virtio_device_ready() in case of the VirtIO backend, right?

How the module driver are probed during device registration is not cristal clear
for me here...
Your approach looks to me a good compromize, I definitively need to apply and
test you patch to well understood the associated scheduling...

Thanks,
Arnaud

> 
> Thanks
> Guennadi
> 
>> Thanks,
>> Arnaud
>>
>>> +		struct rpmsg_channel_info info = {
>>> +			.name = "rpmsg_ns",
>>> +			.src = rpdev->src,
>>> +			.dst = rpdev->dst,
>>> +		};
>>> +
>>> +		rpmsg_unregister_device(rpdev->dev.parent, &info);
>>> +
>>> +		return -ETIMEDOUT;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +EXPORT_SYMBOL(rpmsg_ns_register_device);
>>> +
>>>  /* invoked when a name service announcement arrives */
>>>  static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
>>>  		       void *priv, u32 src)
>>> @@ -76,6 +108,8 @@ static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
>>>  	}
>>>  	rpdev->ept = ns_ept;
>>>  
>>> +	complete(&rpdev->ns_ready);
>>> +
>>>  	return 0;
>>>  }
>>>  
>>> @@ -84,7 +118,7 @@ static struct rpmsg_driver rpmsg_ns_driver = {
>>>  	.probe = rpmsg_ns_probe,
>>>  };
>>>  
>>> -static int rpmsg_ns_init(void)
>>> +int rpmsg_ns_init(void)
>>>  {
>>>  	int ret;
>>>  
>>> @@ -94,15 +128,8 @@ static int rpmsg_ns_init(void)
>>>  
>>>  	return ret;
>>>  }
>>> -postcore_initcall(rpmsg_ns_init);
>>>  
>>> -static void rpmsg_ns_exit(void)
>>> +void rpmsg_ns_exit(void)
>>>  {
>>>  	unregister_rpmsg_driver(&rpmsg_ns_driver);
>>>  }
>>> -module_exit(rpmsg_ns_exit);
>>> -
>>> -MODULE_DESCRIPTION("Name service announcement rpmsg Driver");
>>> -MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
>>> -MODULE_ALIAS("rpmsg_ns");
>>> -MODULE_LICENSE("GPL v2");
>>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> index 10a16be986fc..fdf00cc5f57f 100644
>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> @@ -19,8 +19,8 @@
>>>  #include <linux/mutex.h>
>>>  #include <linux/of_device.h>
>>>  #include <linux/rpmsg.h>
>>> -#include <linux/rpmsg_byteorder.h>
>>> -#include <linux/rpmsg_ns.h>
>>> +#include <linux/rpmsg/byteorder.h>
>>> +#include <linux/rpmsg/ns.h>
>>>  #include <linux/rpmsg/virtio.h>
>>>  #include <linux/scatterlist.h>
>>>  #include <linux/slab.h>
>>> @@ -920,6 +920,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
>>>  	return 0;
>>>  
>>>  free_coherent:
>>> +	kfree(vch);
>>>  	dma_free_coherent(vdev->dev.parent, total_buf_space,
>>>  			  bufs_va, vrp->bufs_dma);
>>>  vqs_del:
>>> diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
>>> index 8ee1b1dab657..71fd15ada5c0 100644
>>> --- a/include/linux/rpmsg.h
>>> +++ b/include/linux/rpmsg.h
>>> @@ -10,6 +10,7 @@
>>>  #ifndef _LINUX_RPMSG_H
>>>  #define _LINUX_RPMSG_H
>>>  
>>> +#include <linux/completion.h>
>>>  #include <linux/types.h>
>>>  #include <linux/device.h>
>>>  #include <linux/err.h>
>>> @@ -17,7 +18,7 @@
>>>  #include <linux/kref.h>
>>>  #include <linux/mutex.h>
>>>  #include <linux/poll.h>
>>> -#include <linux/rpmsg_byteorder.h>
>>> +#include <linux/rpmsg/byteorder.h>
>>>  
>>>  #define RPMSG_ADDR_ANY		0xFFFFFFFF
>>>  
>>> @@ -58,6 +59,7 @@ struct rpmsg_device {
>>>  	struct rpmsg_endpoint *ept;
>>>  	bool announce;
>>>  	bool little_endian;
>>> +	struct completion ns_ready;
>>>  
>>>  	const struct rpmsg_device_ops *ops;
>>>  };
>>> diff --git a/include/linux/rpmsg_byteorder.h b/include/linux/rpmsg/byteorder.h
>>> similarity index 100%
>>> rename from include/linux/rpmsg_byteorder.h
>>> rename to include/linux/rpmsg/byteorder.h
>>> diff --git a/include/linux/rpmsg_ns.h b/include/linux/rpmsg/ns.h
>>> similarity index 82%
>>> rename from include/linux/rpmsg_ns.h
>>> rename to include/linux/rpmsg/ns.h
>>> index 42786bb759b5..2499db0c8c3d 100644
>>> --- a/include/linux/rpmsg_ns.h
>>> +++ b/include/linux/rpmsg/ns.h
>>> @@ -4,8 +4,9 @@
>>>  #define _LINUX_RPMSG_NS_H
>>>  
>>>  #include <linux/mod_devicetable.h>
>>> +#include <linux/rpmsg.h>
>>> +#include <linux/rpmsg/byteorder.h>
>>>  #include <linux/types.h>
>>> -#include <linux/rpmsg_byteorder.h>
>>>  
>>>  /**
>>>   * struct rpmsg_ns_msg - dynamic name service announcement message
>>> @@ -46,14 +47,9 @@ enum rpmsg_ns_flags {
>>>   * This function wraps rpmsg_register_device() preparing the rpdev for use as
>>>   * basis for the rpmsg name service device.
>>>   */
>>> -static inline int rpmsg_ns_register_device(struct rpmsg_device *rpdev)
>>> -{
>>> -       strcpy(rpdev->id.name, "rpmsg_ns");
>>> -       rpdev->driver_override = "rpmsg_ns";
>>> -       rpdev->src = RPMSG_NS_ADDR;
>>> -       rpdev->dst = RPMSG_NS_ADDR;
>>> -
>>> -       return rpmsg_register_device(rpdev);
>>> -}
>>> +int rpmsg_ns_register_device(struct rpmsg_device *rpdev);
>>> +
>>> +int rpmsg_ns_init(void);
>>> +void rpmsg_ns_exit(void);
>>>  
>>>  #endif
>>>