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Date:   Tue, 6 Sep 2022 13:28:27 -0600
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Md Danish Anwar <a0501179@ti.com>
Cc:     Kishon Vijay Abraham I <kishon@ti.com>,
        Md Danish Anwar <danishanwar@ti.com>,
        linux-kernel@vger.kernel.org, bjorn.andersson@linaro.org,
        krzysztof.kozlowski+dt@linaro.org,
        linux-remoteproc@vger.kernel.org, devicetree@vger.kernel.org,
        nm@ti.com, ssantosh@kernel.org, s-anna@ti.com,
        linux-arm-kernel@lists.infradead.org, rogerq@kernel.org,
        grygorii.strashko@ti.com, vigneshr@ti.com, robh@kernel.org
Subject: Re: [PATCH v5 2/6] remoteproc: pru: Add APIs to get and put the PRU
 cores
Message-ID: <20220906192827.GA65147@p14s>
References: <20220607045650.4999-1-p-mohan@ti.com>
 <20220607045650.4999-3-p-mohan@ti.com>
 <20220712175949.GB2945984@p14s>
 <20220714172015.GA3106020@p14s>
 <20c544ef-40b3-dcbc-1f29-aac140725b57@ti.com>
 <7e7ed572-93fe-a9c8-f11e-d555e5113fd1@ti.com>
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In-Reply-To: <7e7ed572-93fe-a9c8-f11e-d555e5113fd1@ti.com>
Precedence: bulk

On Fri, Sep 02, 2022 at 03:09:04PM +0530, Md Danish Anwar wrote:
> 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@ti.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@ti.com>
> > > > > Signed-off-by: Suman Anna <s-anna@ti.com>
> > > > > Signed-off-by: Tero Kristo <t-kristo@ti.com>
> > > > > Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
> > > > > Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
> > > > > Co-developed-by: Puranjay Mohan <p-mohan@ti.com>
> > > > > Signed-off-by: Puranjay Mohan <p-mohan@ti.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@ti.com>
> > > > >    *	Andrew F. Davis <afd@ti.com>
> > > > >    *	Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org> for Texas Instruments
> > > > > + *	Puranjay Mohan <p-mohan@ti.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().
>

Not optimal.

> 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.
> 

Not optimal.

> 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.
> 

Unacceptable for the reason I already stated.  

> Please let me know which option to continue with.

I suggest building a wrapper that does everything you want around rproc_get_by_phandle().

> 
> 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@ti.com>");
> > > > >   MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
> > > > >   MODULE_AUTHOR("Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>");
> > > > > +MODULE_AUTHOR("Puranjay Mohan <p-mohan@ti.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@ti.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
> > > > >