Date:   Fri, 2 Sep 2022 15:09:04 +0530
From:   Md Danish Anwar <a0501179@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Md Danish Anwar <danishanwar@...com>
CC:     <linux-kernel@...r.kernel.org>, <bjorn.andersson@...aro.org>,
        <krzysztof.kozlowski+dt@...aro.org>,
        <linux-remoteproc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <nm@...com>, <ssantosh@...nel.org>, <s-anna@...com>,
        <linux-arm-kernel@...ts.infradead.org>, <rogerq@...nel.org>,
        <grygorii.strashko@...com>, <vigneshr@...com>, <robh@...nel.org>
Subject: Re: [PATCH v5 2/6] remoteproc: pru: Add APIs to get and put the PRU
 cores

Hi Mathieu,


On 15/07/22 11:52, Kishon Vijay Abraham I wrote:
> +Danish
> 
> Hi Mathieu,
> 
> On 14/07/22 22:50, Mathieu Poirier wrote:
>> On Tue, Jul 12, 2022 at 11:59:49AM -0600, Mathieu Poirier wrote:
>>> Hi Puranjay,
> 
> Removed Puranjay (as he is no longer with TI) and adding Danish.
> 
> Regards,
> Kishon
>>>
>>> On Tue, Jun 07, 2022 at 10:26:46AM +0530, Puranjay Mohan wrote:
>>>> From: Tero Kristo <t-kristo@...com>
>>>>
>>>> Add two new APIs, pru_rproc_get() and pru_rproc_put(), to the PRU
>>>> driver to allow client drivers to acquire and release the remoteproc
>>>> device associated with a PRU core. The PRU cores are treated as
>>>> resources with only one client owning it at a time.
>>>>
>>>> The pru_rproc_get() function returns the rproc handle corresponding
>>>> to a PRU core identified by the device tree "ti,prus" property under
>>>> the client node. The pru_rproc_put() is the complementary function
>>>> to pru_rproc_get().
>>>>
>>>> Co-developed-by: Suman Anna <s-anna@...com>
>>>> Signed-off-by: Suman Anna <s-anna@...com>
>>>> Signed-off-by: Tero Kristo <t-kristo@...com>
>>>> Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
>>>> Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
>>>> Co-developed-by: Puranjay Mohan <p-mohan@...com>
>>>> Signed-off-by: Puranjay Mohan <p-mohan@...com>
>>>> ---
>>>>   drivers/remoteproc/pru_rproc.c | 138 +++++++++++++++++++++++++++++++--
>>>>   include/linux/pruss.h          |  56 +++++++++++++
>>>>   2 files changed, 189 insertions(+), 5 deletions(-)
>>>>   create mode 100644 include/linux/pruss.h
>>>>
>>>> diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
>>>> index 1777a01fa84e..7a35b400287a 100644
>>>> --- a/drivers/remoteproc/pru_rproc.c
>>>> +++ b/drivers/remoteproc/pru_rproc.c
>>>> @@ -2,12 +2,13 @@
>>>>   /*
>>>>    * PRU-ICSS remoteproc driver for various TI SoCs
>>>>    *
>>>> - * Copyright (C) 2014-2020 Texas Instruments Incorporated - https://www.ti.com/
>>>> + * Copyright (C) 2014-2022 Texas Instruments Incorporated - https://www.ti.com/
>>>>    *
>>>>    * Author(s):
>>>>    *	Suman Anna <s-anna@...com>
>>>>    *	Andrew F. Davis <afd@...com>
>>>>    *	Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org> for Texas Instruments
>>>> + *	Puranjay Mohan <p-mohan@...com>
>>>>    */
>>>>   
>>>>   #include <linux/bitops.h>
>>>> @@ -16,6 +17,7 @@
>>>>   #include <linux/module.h>
>>>>   #include <linux/of_device.h>
>>>>   #include <linux/of_irq.h>
>>>> +#include <linux/pruss.h>
>>>>   #include <linux/pruss_driver.h>
>>>>   #include <linux/remoteproc.h>
>>>>   
>>>> @@ -111,6 +113,8 @@ struct pru_private_data {
>>>>    * @rproc: remoteproc pointer for this PRU core
>>>>    * @data: PRU core specific data
>>>>    * @mem_regions: data for each of the PRU memory regions
>>>> + * @client_np: client device node
>>>> + * @lock: mutex to protect client usage
>>>>    * @fw_name: name of firmware image used during loading
>>>>    * @mapped_irq: virtual interrupt numbers of created fw specific mapping
>>>>    * @pru_interrupt_map: pointer to interrupt mapping description (firmware)
>>>> @@ -126,6 +130,8 @@ struct pru_rproc {
>>>>   	struct rproc *rproc;
>>>>   	const struct pru_private_data *data;
>>>>   	struct pruss_mem_region mem_regions[PRU_IOMEM_MAX];
>>>> +	struct device_node *client_np;
>>>> +	struct mutex lock; /* client access lock */
>>>>   	const char *fw_name;
>>>>   	unsigned int *mapped_irq;
>>>>   	struct pru_irq_rsc *pru_interrupt_map;
>>>> @@ -146,6 +152,125 @@ void pru_control_write_reg(struct pru_rproc *pru, unsigned int reg, u32 val)
>>>>   	writel_relaxed(val, pru->mem_regions[PRU_IOMEM_CTRL].va + reg);
>>>>   }
>>>>   
>>>> +static struct rproc *__pru_rproc_get(struct device_node *np, int index)
>>>> +{
>>>> +	struct device_node *rproc_np = NULL;
>>>> +	struct platform_device *pdev;
>>>> +	struct rproc *rproc;
>>>> +
>>>> +	rproc_np = of_parse_phandle(np, "ti,prus", index);
>>>> +	if (!rproc_np || !of_device_is_available(rproc_np))
>>>> +		return ERR_PTR(-ENODEV);
>>>> +
>>>> +	pdev = of_find_device_by_node(rproc_np);
>>>> +	of_node_put(rproc_np);
>>>> +
>>>> +	if (!pdev || !(&pdev->dev) || !((&pdev->dev)->driver))
>>>> +		/* probably PRU not yet probed */
>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>> +
>>>> +	/* make sure it is PRU rproc */
>>>> +	if (!is_pru_rproc(&pdev->dev)) {
>>>> +		put_device(&pdev->dev);
>>>> +		return ERR_PTR(-ENODEV);
>>>> +	}
>>>> +
>>>> +	rproc = platform_get_drvdata(pdev);
>>>> +	put_device(&pdev->dev);
>>>> +	if (!rproc)
>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>> +
>>>> +	get_device(&rproc->dev);
>>>> +
>>>> +	return rproc;
>>>> +}
>>>> +
>>>> +/**
>>>> + * pru_rproc_get() - get the PRU rproc instance from a device node
>>>> + * @np: the user/client device node
>>>> + * @index: index to use for the ti,prus property
>>>> + * @pru_id: optional pointer to return the PRU remoteproc processor id
>>>> + *
>>>> + * This function looks through a client device node's "ti,prus" property at
>>>> + * index @index and returns the rproc handle for a valid PRU remote processor if
>>>> + * found. The function allows only one user to own the PRU rproc resource at a
>>>> + * time. Caller must call pru_rproc_put() when done with using the rproc, not
>>>> + * required if the function returns a failure.
>>>> + *
>>>> + * When optional @pru_id pointer is passed the PRU remoteproc processor id is
>>>> + * returned.
>>>> + *
>>>> + * Return: rproc handle on success, and an ERR_PTR on failure using one
>>>> + * of the following error values
>>>> + *    -ENODEV if device is not found
>>>> + *    -EBUSY if PRU is already acquired by anyone
>>>> + *    -EPROBE_DEFER is PRU device is not probed yet
>>>> + */
>>>> +struct rproc *pru_rproc_get(struct device_node *np, int index,
>>>> +			    enum pruss_pru_id *pru_id)
>>>> +{
>>>> +	struct rproc *rproc;
>>>> +	struct pru_rproc *pru;
>>>> +	struct device *dev;
>>>> +
>>>> +	try_module_get(THIS_MODULE);
>>>
>>> There should be a module_put() in pru_rproc_put()...
>>
>> ... and in the error path of this function.
>>
>>>
>>> More comments to come tomorrow.  I'm especially worried about this API racing
>>> with a remote processor being removed or detached.
>>>
>>
>> Looking at what is done in wkup_m3_ipc_probe(), it should be possible to call
>> rproc_get_by_handle() here and that would make sure the remote processor doesn't
>> go away before the end of the function.
>>
>> More comments to come...

It is possible to call rproc_get_by_handle() here instead of 
__pru_get_proc(), but that would not provide multiple functionality.

The API rproc_get_by_handle() returns rproc handle on success, and NULL 
on failure where as __pru_get_proc() returns ERR_PTR on failure which 
provides multiple functionality and opportunity for us to distinguish 
between multiple errors.

So we have these three options.

1. If we're using the API rproc_get_by_handle() and we want the multiple 
ERR_PTR on failure then we will need to change the API 
rproc_get_by_handle() and also all the functions that uses 
rproc_get_by_handle().

2. Keep the API rproc_get_by_handle() as it is. That will restrict us 
from using multiple ERR_PTR on different kinds of error.

3. Instead of using rproc_get_by_handle(), keep using __pru_get_proc(). 
This will make sure we have the proper ERR_PTR to retrun for different 
kinds of errors.

Please let me know which option to continue with.

Thanks,
Danish


>>
>>
>>> Thanks,
>>> Mathieu
>>>
>>>> +
>>>> +	rproc = __pru_rproc_get(np, index);
>>>> +	if (IS_ERR(rproc))
>>>> +		return rproc;
>>>> +
>>>> +	pru = rproc->priv;
>>>> +	dev = &rproc->dev;
>>>> +
>>>> +	mutex_lock(&pru->lock);
>>>> +
>>>> +	if (pru->client_np) {
>>>> +		mutex_unlock(&pru->lock);
>>>> +		put_device(dev);
>>>> +		return ERR_PTR(-EBUSY);
>>>> +	}
>>>> +
>>>> +	pru->client_np = np;
>>>> +
>>>> +	mutex_unlock(&pru->lock);
>>>> +
>>>> +	if (pru_id)
>>>> +		*pru_id = pru->id;
>>>> +
>>>> +	return rproc;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(pru_rproc_get);
>>>> +
>>>> +/**
>>>> + * pru_rproc_put() - release the PRU rproc resource
>>>> + * @rproc: the rproc resource to release
>>>> + *
>>>> + * Releases the PRU rproc resource and makes it available to other
>>>> + * users.
>>>> + */
>>>> +void pru_rproc_put(struct rproc *rproc)
>>>> +{
>>>> +	struct pru_rproc *pru;
>>>> +
>>>> +	if (IS_ERR_OR_NULL(rproc) || !is_pru_rproc(rproc->dev.parent))
>>>> +		return;
>>>> +
>>>> +	pru = rproc->priv;
>>>> +
>>>> +	mutex_lock(&pru->lock);
>>>> +
>>>> +	if (!pru->client_np) {
>>>> +		mutex_unlock(&pru->lock);
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	pru->client_np = NULL;
>>>> +	mutex_unlock(&pru->lock);
>>>> +
>>>> +	put_device(&rproc->dev);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(pru_rproc_put);
>>>> +
>>>>   static inline u32 pru_debug_read_reg(struct pru_rproc *pru, unsigned int reg)
>>>>   {
>>>>   	return readl_relaxed(pru->mem_regions[PRU_IOMEM_DEBUG].va + reg);
>>>> @@ -438,7 +563,7 @@ static void *pru_d_da_to_va(struct pru_rproc *pru, u32 da, size_t len)
>>>>   	dram0 = pruss->mem_regions[PRUSS_MEM_DRAM0];
>>>>   	dram1 = pruss->mem_regions[PRUSS_MEM_DRAM1];
>>>>   	/* PRU1 has its local RAM addresses reversed */
>>>> -	if (pru->id == 1)
>>>> +	if (pru->id == PRUSS_PRU1)
>>>>   		swap(dram0, dram1);
>>>>   	shrd_ram = pruss->mem_regions[PRUSS_MEM_SHRD_RAM2];
>>>>   
>>>> @@ -747,14 +872,14 @@ static int pru_rproc_set_id(struct pru_rproc *pru)
>>>>   	case RTU0_IRAM_ADDR_MASK:
>>>>   		fallthrough;
>>>>   	case PRU0_IRAM_ADDR_MASK:
>>>> -		pru->id = 0;
>>>> +		pru->id = PRUSS_PRU0;
>>>>   		break;
>>>>   	case TX_PRU1_IRAM_ADDR_MASK:
>>>>   		fallthrough;
>>>>   	case RTU1_IRAM_ADDR_MASK:
>>>>   		fallthrough;
>>>>   	case PRU1_IRAM_ADDR_MASK:
>>>> -		pru->id = 1;
>>>> +		pru->id = PRUSS_PRU1;
>>>>   		break;
>>>>   	default:
>>>>   		ret = -EINVAL;
>>>> @@ -816,6 +941,8 @@ static int pru_rproc_probe(struct platform_device *pdev)
>>>>   	pru->pruss = platform_get_drvdata(ppdev);
>>>>   	pru->rproc = rproc;
>>>>   	pru->fw_name = fw_name;
>>>> +	pru->client_np = NULL;
>>>> +	mutex_init(&pru->lock);
>>>>   
>>>>   	for (i = 0; i < ARRAY_SIZE(mem_names); i++) {
>>>>   		res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
>>>> @@ -903,7 +1030,7 @@ MODULE_DEVICE_TABLE(of, pru_rproc_match);
>>>>   
>>>>   static struct platform_driver pru_rproc_driver = {
>>>>   	.driver = {
>>>> -		.name   = "pru-rproc",
>>>> +		.name   = PRU_RPROC_DRVNAME,
>>>>   		.of_match_table = pru_rproc_match,
>>>>   		.suppress_bind_attrs = true,
>>>>   	},
>>>> @@ -915,5 +1042,6 @@ module_platform_driver(pru_rproc_driver);
>>>>   MODULE_AUTHOR("Suman Anna <s-anna@...com>");
>>>>   MODULE_AUTHOR("Andrew F. Davis <afd@...com>");
>>>>   MODULE_AUTHOR("Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>");
>>>> +MODULE_AUTHOR("Puranjay Mohan <p-mohan@...com>");
>>>>   MODULE_DESCRIPTION("PRU-ICSS Remote Processor Driver");
>>>>   MODULE_LICENSE("GPL v2");
>>>> diff --git a/include/linux/pruss.h b/include/linux/pruss.h
>>>> new file mode 100644
>>>> index 000000000000..fdc719b43db0
>>>> --- /dev/null
>>>> +++ b/include/linux/pruss.h
>>>> @@ -0,0 +1,56 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>>> +/**
>>>> + * PRU-ICSS Subsystem user interfaces
>>>> + *
>>>> + * Copyright (C) 2015-2022 Texas Instruments Incorporated - http://www.ti.com
>>>> + *	Suman Anna <s-anna@...com>
>>>> + */
>>>> +
>>>> +#ifndef __LINUX_PRUSS_H
>>>> +#define __LINUX_PRUSS_H
>>>> +
>>>> +#include <linux/device.h>
>>>> +#include <linux/types.h>
>>>> +
>>>> +#define PRU_RPROC_DRVNAME "pru-rproc"
>>>> +
>>>> +/*
>>>> + * enum pruss_pru_id - PRU core identifiers
>>>> + */
>>>> +enum pruss_pru_id {
>>>> +	PRUSS_PRU0 = 0,
>>>> +	PRUSS_PRU1,
>>>> +	PRUSS_NUM_PRUS,
>>>> +};
>>>> +
>>>> +struct device_node;
>>>> +
>>>> +#if IS_ENABLED(CONFIG_PRU_REMOTEPROC)
>>>> +
>>>> +struct rproc *pru_rproc_get(struct device_node *np, int index,
>>>> +			    enum pruss_pru_id *pru_id);
>>>> +void pru_rproc_put(struct rproc *rproc);
>>>> +
>>>> +#else
>>>> +
>>>> +static inline struct rproc *
>>>> +pru_rproc_get(struct device_node *np, int index, enum pruss_pru_id *pru_id)
>>>> +{
>>>> +	return ERR_PTR(-EOPNOTSUPP);
>>>> +}
>>>> +
>>>> +static inline void pru_rproc_put(struct rproc *rproc) { }
>>>> +
>>>> +#endif /* CONFIG_PRU_REMOTEPROC */
>>>> +
>>>> +static inline bool is_pru_rproc(struct device *dev)
>>>> +{
>>>> +	const char *drv_name = dev_driver_string(dev);
>>>> +
>>>> +	if (strncmp(drv_name, PRU_RPROC_DRVNAME, sizeof(PRU_RPROC_DRVNAME)))
>>>> +		return false;
>>>> +
>>>> +	return true;
>>>> +}
>>>> +
>>>> +#endif /* __LINUX_PRUSS_H */
>>>> -- 
>>>> 2.17.1
>>>>

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