Date:   Tue, 19 Jul 2022 09:53:40 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Puranjay Mohan <p-mohan@...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, kishon@...com,
        robh@...nel.org
Subject: Re: [PATCH v5 4/6] remoteproc: pru: Add pru_rproc_set_ctable()
 function

On Tue, Jun 07, 2022 at 10:26:48AM +0530, Puranjay Mohan wrote:
> From: Roger Quadros <rogerq@...com>
> 
> Some firmwares expect the OS drivers to configure the CTABLE
> entries publishing dynamically allocated memory regions. For
> example, the PRU Ethernet firmwares use the C28 and C30 entries
> for retrieving the Shared RAM and System SRAM (OCMC) areas
> allocated by the PRU Ethernet client driver.
> 
> Provide a way for users to do that through a new API,
> pru_rproc_set_ctable(). The API returns 0 on success and
> a negative value on error.
> 
> NOTE:
> The programmable CTABLE entries are typically re-programmed by
> the PRU firmwares when dealing with a certain block of memory
> during block processing. This API provides an interface to the
> PRU client drivers to publish a dynamically allocated memory
> block with the PRU firmware using a CTABLE entry instead of a
> negotiated address in shared memory. Additional synchronization
> may be needed between the PRU client drivers and firmwares if
> different addresses needs to be published at run-time reusing
> the same CTABLE entry.

In all this the concept of a "ctable" is not explained and as such, I have to
guess it stands for "constant table".  I also have to guess this table stores
memory addresses known to other drivers, making it possible to boot a system
without all components having access to a DT.  Again, those are all guesses
because it is not explained.  And all that guessing makes reviewing this small
patchset quite difficult.

> 
> Co-developed-by: Andrew F. Davis <afd@...com>
> Signed-off-by: Andrew F. Davis <afd@...com>
> Co-developed-by: Suman Anna <s-anna@...com>
> Signed-off-by: Suman Anna <s-anna@...com>
> Signed-off-by: Roger Quadros <rogerq@...com>
> Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
> Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
> Signed-off-by: Puranjay Mohan <p-mohan@...com>
> ---
>  drivers/remoteproc/pru_rproc.c | 59 ++++++++++++++++++++++++++++++++++
>  include/linux/pruss.h          | 22 +++++++++++++
>  2 files changed, 81 insertions(+)
> 
> diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
> index 9fed3e0372d3..d06b763e995e 100644
> --- a/drivers/remoteproc/pru_rproc.c
> +++ b/drivers/remoteproc/pru_rproc.c
> @@ -119,6 +119,7 @@ struct pru_private_data {
>   * @mapped_irq: virtual interrupt numbers of created fw specific mapping
>   * @pru_interrupt_map: pointer to interrupt mapping description (firmware)
>   * @pru_interrupt_map_sz: pru_interrupt_map size
> + * @rmw_lock: lock for read, modify, write operations on registers
>   * @dbg_single_step: debug state variable to set PRU into single step mode
>   * @dbg_continuous: debug state variable to restore PRU execution mode
>   * @evt_count: number of mapped events
> @@ -136,6 +137,7 @@ struct pru_rproc {
>  	unsigned int *mapped_irq;
>  	struct pru_irq_rsc *pru_interrupt_map;
>  	size_t pru_interrupt_map_sz;
> +	spinlock_t rmw_lock; /* register access lock */
>  	u32 dbg_single_step;
>  	u32 dbg_continuous;
>  	u8 evt_count;
> @@ -152,6 +154,23 @@ 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 inline
> +void pru_control_set_reg(struct pru_rproc *pru, unsigned int reg,
> +			 u32 mask, u32 set)
> +{
> +	u32 val;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&pru->rmw_lock, flags);
> +
> +	val = pru_control_read_reg(pru, reg);
> +	val &= ~mask;
> +	val |= (set & mask);
> +	pru_control_write_reg(pru, reg, val);
> +
> +	spin_unlock_irqrestore(&pru->rmw_lock, flags);
> +}
> +
>  static struct rproc *__pru_rproc_get(struct device_node *np, int index)
>  {
>  	struct device_node *rproc_np = NULL;
> @@ -273,6 +292,45 @@ void pru_rproc_put(struct rproc *rproc)
>  }
>  EXPORT_SYMBOL_GPL(pru_rproc_put);
>  
> +/**
> + * pru_rproc_set_ctable() - set the constant table index for the PRU
> + * @rproc: the rproc instance of the PRU
> + * @c: constant table index to set
> + * @addr: physical address to set it to
> + *
> + * Return: 0 on success, or errno in error case.
> + */
> +int pru_rproc_set_ctable(struct rproc *rproc, enum pru_ctable_idx c, u32 addr)
> +{
> +	struct pru_rproc *pru = rproc->priv;
> +	unsigned int reg;
> +	u32 mask, set;
> +	u16 idx;
> +	u16 idx_mask;
> +
> +	if (IS_ERR_OR_NULL(rproc))
> +		return -EINVAL;
> +
> +	if (!rproc->dev.parent || !is_pru_rproc(rproc->dev.parent))
> +		return -ENODEV;
> +
> +	/* pointer is 16 bit and index is 8-bit so mask out the rest */
> +	idx_mask = (c >= PRU_C28) ? 0xFFFF : 0xFF;
> +
> +	/* ctable uses bit 8 and upwards only */
> +	idx = (addr >> 8) & idx_mask;
> +
> +	/* configurable ctable (i.e. C24) starts at PRU_CTRL_CTBIR0 */
> +	reg = PRU_CTRL_CTBIR0 + 4 * (c >> 1);
> +	mask = idx_mask << (16 * (c & 1));
> +	set = idx << (16 * (c & 1));
> +

Please add comments that describe the content and format of the CTABLE.
Otherwise this code becomes unmaintainable.

> +	pru_control_set_reg(pru, reg, mask, set);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(pru_rproc_set_ctable);
> +
>  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);
> @@ -944,6 +1002,7 @@ static int pru_rproc_probe(struct platform_device *pdev)
>  	pru->rproc = rproc;
>  	pru->fw_name = fw_name;
>  	pru->client_np = NULL;
> +	spin_lock_init(&pru->rmw_lock);
>  	mutex_init(&pru->lock);
>  
>  	for (i = 0; i < ARRAY_SIZE(mem_names); i++) {
> diff --git a/include/linux/pruss.h b/include/linux/pruss.h
> index fdc719b43db0..d830e20056c7 100644
> --- a/include/linux/pruss.h
> +++ b/include/linux/pruss.h
> @@ -23,13 +23,29 @@ enum pruss_pru_id {
>  	PRUSS_NUM_PRUS,
>  };
>  
> +/*
> + * enum pru_ctable_idx - Configurable Constant table index identifiers
> + */
> +enum pru_ctable_idx {
> +	PRU_C24 = 0,
> +	PRU_C25,
> +	PRU_C26,
> +	PRU_C27,
> +	PRU_C28,
> +	PRU_C29,
> +	PRU_C30,
> +	PRU_C31,
> +};
> +
>  struct device_node;
> +struct rproc;
>  
>  #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);
> +int pru_rproc_set_ctable(struct rproc *rproc, enum pru_ctable_idx c, u32 addr);
>  
>  #else
>  
> @@ -41,6 +57,12 @@ pru_rproc_get(struct device_node *np, int index, enum pruss_pru_id *pru_id)
>  
>  static inline void pru_rproc_put(struct rproc *rproc) { }
>  
> +static inline int pru_rproc_set_ctable(struct rproc *rproc,
> +				       enum pru_ctable_idx c, u32 addr)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  #endif /* CONFIG_PRU_REMOTEPROC */
>  
>  static inline bool is_pru_rproc(struct device *dev)
> -- 
> 2.17.1
> 

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