Re: [RFC PATCH 5/5] PCI: rcar-ep: Add support for DMAC

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Wed, Jan 26, 2022 at 07:50:43PM +0000, Lad Prabhakar wrote:
> R-Car PCIe controller has an internal DMAC to support data transfer
> between Internal Bus -> PCI Express and vice versa.
> 
> This patch fills in the required flags and ops for the PCIe EP to
> support DMAC transfer.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
>  drivers/pci/controller/pcie-rcar-ep.c | 227 ++++++++++++++++++++++++++
>  drivers/pci/controller/pcie-rcar.h    |  23 +++
>  2 files changed, 250 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-rcar-ep.c b/drivers/pci/controller/pcie-rcar-ep.c
> index f9682df1da61..c49b25069328 100644
> --- a/drivers/pci/controller/pcie-rcar-ep.c
> +++ b/drivers/pci/controller/pcie-rcar-ep.c
> @@ -18,6 +18,21 @@
>  
>  #define RCAR_EPC_MAX_FUNCTIONS		1
>  
> +#define RCAR_PCIE_MAX_DMAC_BYTE_COUNT		0x7FFFFFFU
> +#define RCAR_PCIE_DMAC_BYTE_COUNT_MULTIPLE	8
> +#define RCAR_PCIE_DMAC_TIMEOUT			(msecs_to_jiffies(3 * 1000))
> +#define RCAR_PCIE_DMAC_DEFAULT_CHANNEL		0
> +
> +enum rcar_pcie_ep_dmac_xfr_status {
> +	RCAR_PCIE_DMA_XFR_SUCCESS,
> +	RCAR_PCIE_DMA_XFR_ERROR,
> +};
> +
> +struct rcar_pcie_ep_dmac_info {
> +	enum rcar_pcie_ep_dmac_xfr_status status;
> +	size_t bytes;
> +};
> +
>  /* Structure representing the PCIe interface */
>  struct rcar_pcie_endpoint {
>  	struct rcar_pcie	pcie;
> @@ -28,8 +43,114 @@ struct rcar_pcie_endpoint {
>  	unsigned long		*ib_window_map;
>  	u32			num_ib_windows;
>  	u32			num_ob_windows;
> +	struct completion	irq_raised;
> +	struct mutex		dma_operation;
> +	spinlock_t		lock;

Locks should be documented.

> +	struct rcar_pcie_ep_dmac_info xfr;
>  };
>  
> +static inline bool rcar_pcie_ep_is_dmac_active(struct rcar_pcie_endpoint *ep)

No need of "inline", compiler should be able to judge it.

> +{
> +	if (rcar_pci_read_reg(&ep->pcie, PCIEDMAOR) & PCIEDMAOR_DMAACT)
> +		return true;
> +
> +	return false;
> +}
> +
> +static void
> +rcar_pcie_ep_setup_dmac_request(struct rcar_pcie_endpoint *ep,
> +				dma_addr_t dma_dst, dma_addr_t dma_src,
> +				size_t len, enum pci_epf_xfr_direction dir, u8 ch)
> +{
> +	struct rcar_pcie *pcie = &ep->pcie;
> +	u32 val;
> +
> +	ep->xfr.status = RCAR_PCIE_DMA_XFR_ERROR;
> +	ep->xfr.bytes = RCAR_PCIE_MAX_DMAC_BYTE_COUNT;
> +
> +	/* swap values if xfr is from pcie to internal */
> +	if (dir == PCIE_TO_INTERNAL)
> +		swap(dma_dst, dma_src);
> +
> +	/* Configure the PCI Express lower */
> +	rcar_pci_write_reg(pcie, lower_32_bits(dma_dst), PCIEDMPALR(ch));
> +
> +	/* Configure the PCI Express upper */
> +	rcar_pci_write_reg(pcie, upper_32_bits(dma_dst), PCIEDMPAUR(ch));
> +
> +	/* Configure the internal bus address */
> +	rcar_pci_write_reg(pcie, lower_32_bits(dma_src), PCIEDMIAR(ch));
> +
> +	/* Configure the byte count values */
> +	rcar_pci_write_reg(pcie, len, PCIEDMBCNTR(ch));
> +
> +	/* Enable interrupts */
> +	val = rcar_pci_read_reg(pcie, PCIEDMCHSR(ch));
> +
> +	/* set enable flags */
> +	val |= PCIEDMCHSR_IE;
> +	val |= PCIEDMCHSR_IBEE;
> +	val |= PCIEDMCHSR_PEEE;
> +	val |= PCIEDMCHSR_CHTCE;
> +
> +	/* Clear error flags */
> +	val &= ~PCIEDMCHSR_TE;
> +	val &= ~PCIEDMCHSR_PEE;
> +	val &= ~PCIEDMCHSR_IBE;
> +	val &= ~PCIEDMCHSR_CHTC;
> +

Can you use bitfield operations everywhere?

> +	rcar_pci_write_reg(pcie, val, PCIEDMCHSR(ch));
> +
> +	wmb(); /* flush the settings */

Since the write is at the end of the function, no need to put a barrier here.

> +}
> +
> +static void rcar_pcie_ep_execute_dmac_request(struct rcar_pcie_endpoint *ep,
> +					      enum pci_epf_xfr_direction dir, u8 ch)
> +{
> +	struct rcar_pcie *pcie = &ep->pcie;
> +	u32 val;
> +
> +	/* Enable DMA */
> +	val = rcar_pci_read_reg(pcie, PCIEDMAOR);
> +	val |= PCIEDMAOR_DMAE;
> +	rcar_pci_write_reg(pcie, val, PCIEDMAOR);
> +
> +	/* Configure the DMA direction */
> +	val = rcar_pci_read_reg(pcie, PCIEDMCHCR(ch));
> +	if (dir == INTERNAL_TO_PCIE)
> +		val |= PCIEDMCHCR_DIR;
> +	else
> +		val &= ~PCIEDMCHCR_DIR;
> +
> +	val |= PCIEDMCHCR_CHE;
> +	rcar_pci_write_reg(pcie, val, PCIEDMCHCR(ch));
> +
> +	wmb(); /* flush the settings */

Same here.

> +}
> +
> +static enum rcar_pcie_ep_dmac_xfr_status
> +rcar_pcie_ep_get_dmac_status(struct rcar_pcie_endpoint *ep,
> +			     size_t *count, u8 ch)

ch is unused.

> +{
> +	*count = ep->xfr.bytes;
> +	return ep->xfr.status;
> +}
> +
> +static void rcar_pcie_ep_stop_dmac_request(struct rcar_pcie_endpoint *ep, u8 ch)
> +{
> +	struct rcar_pcie *pcie = &ep->pcie;
> +	u32 val;
> +
> +	val = rcar_pci_read_reg(pcie, PCIEDMCHCR(ch));
> +	val &= ~PCIEDMCHCR_CHE;
> +	rcar_pci_write_reg(pcie, val, PCIEDMCHCR(ch));
> +
> +	/* Disable interrupt */
> +	val = rcar_pci_read_reg(pcie, PCIEDMAOR);
> +	val &= ~PCIEDMAOR_DMAE;
> +	rcar_pci_write_reg(pcie, val, PCIEDMAOR);
> +}
> +
>  static void rcar_pcie_ep_hw_init(struct rcar_pcie *pcie)
>  {
>  	u32 val;
> @@ -419,6 +540,44 @@ static int rcar_pcie_ep_raise_irq(struct pci_epc *epc, u8 fn, u8 vfn,
>  	}
>  }
>  
> +static int rcar_pcie_ep_data_transfer(struct pci_epc *epc, struct pci_epf *epf,
> +				      dma_addr_t dma_dst, dma_addr_t dma_src,
> +				      size_t len, enum pci_epf_xfr_direction dir)
> +{
> +	struct rcar_pcie_endpoint *ep = epc_get_drvdata(epc);
> +	u8 ch = RCAR_PCIE_DMAC_DEFAULT_CHANNEL;
> +	enum rcar_pcie_ep_dmac_xfr_status stat;
> +	int ret = -EINVAL;
> +	long wait_status;
> +	size_t count;
> +
> +	if (len > RCAR_PCIE_MAX_DMAC_BYTE_COUNT ||
> +	    (len % RCAR_PCIE_DMAC_BYTE_COUNT_MULTIPLE) != 0)
> +		return -EINVAL;

A comment here would be informative.

> +
> +	if (mutex_is_locked(&ep->dma_operation) || rcar_pcie_ep_is_dmac_active(ep))

Why the mutex should be checked here? Why can't this thread sleep below if mutex
is not available?

> +		return -EBUSY;
> +
> +	mutex_lock(&ep->dma_operation);
> +
> +	rcar_pcie_ep_setup_dmac_request(ep, dma_dst, dma_src, len, dir, ch);
> +
> +	rcar_pcie_ep_execute_dmac_request(ep, dir, ch);
> +
> +	wait_status = wait_for_completion_interruptible_timeout(&ep->irq_raised,
> +								RCAR_PCIE_DMAC_TIMEOUT);
> +	if (wait_status <= 0) {
> +		rcar_pcie_ep_stop_dmac_request(ep, ch);

ret = -ETIMEDOUT;?

> +	} else {
> +		stat = rcar_pcie_ep_get_dmac_status(ep, &count, ch);
> +		if (stat == RCAR_PCIE_DMA_XFR_SUCCESS && !count)
> +			ret = 0;
> +	}
> +
> +	mutex_unlock(&ep->dma_operation);
> +	return ret;
> +}
> +
>  static int rcar_pcie_ep_start(struct pci_epc *epc)
>  {
>  	struct rcar_pcie_endpoint *ep = epc_get_drvdata(epc);
> @@ -429,6 +588,55 @@ static int rcar_pcie_ep_start(struct pci_epc *epc)
>  	return 0;
>  }
>  
> +static irqreturn_t rcar_pcie_ep_dmac_irq_handler(int irq, void *arg)
> +{
> +	u8 ch = RCAR_PCIE_DMAC_DEFAULT_CHANNEL;
> +	struct rcar_pcie_endpoint *ep = arg;
> +	struct rcar_pcie *pcie = &ep->pcie;
> +	unsigned long flags;
> +	u32 chsr_val;
> +	u32 chcr_val;
> +	u32 bytes;
> +
> +	spin_lock_irqsave(&ep->lock, flags);

Since the lock is taken in isr, there is no need to do irqsave/restore.
Just spin_lock/unlock is enough.

Also, this lock is only used in isr. I'm wondering why the lock is needed.

> +
> +	chsr_val = rcar_pci_read_reg(pcie, PCIEDMCHSR(ch));
> +
> +	chcr_val = rcar_pci_read_reg(pcie, PCIEDMCHCR(ch));
> +
> +	if (mutex_is_locked(&ep->dma_operation)) {

Why should the mutex be checked? Are you expecting the irq after transfer
timeout?

> +		if ((chsr_val &  PCIEDMCHSR_PEE) ||
> +		    (chsr_val & PCIEDMCHSR_IBE) ||
> +		    (chsr_val & PCIEDMCHSR_CHTC))
> +			ep->xfr.status = RCAR_PCIE_DMA_XFR_ERROR;
> +		else if (chsr_val & PCIEDMCHSR_TE)
> +			ep->xfr.status = RCAR_PCIE_DMA_XFR_SUCCESS;
> +
> +		/* get byte count */
> +		bytes = rcar_pci_read_reg(pcie, PCIEDMBCNTR(ch));
> +		ep->xfr.bytes = bytes;
> +
> +		if ((chsr_val & PCIEDMCHSR_PEE) || (chsr_val & PCIEDMCHSR_IBE) ||
> +		    (chsr_val & PCIEDMCHSR_TE) || (chsr_val & PCIEDMCHSR_CHTC)) {
> +			complete(&ep->irq_raised);
> +		}
> +	} else {
> +		spin_unlock_irqrestore(&ep->lock, flags);
> +		return IRQ_NONE;
> +	}
> +
> +	if (chcr_val & PCIEDMCHCR_CHE)
> +		chcr_val &= ~PCIEDMCHCR_CHE;
> +	rcar_pci_write_reg(pcie, chcr_val, PCIEDMCHCR(ch));
> +
> +	/* Clear DMA interrupt source */
> +	rcar_pci_write_reg(pcie, chsr_val, PCIEDMCHSR(ch));
> +
> +	spin_unlock_irqrestore(&ep->lock, flags);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static void rcar_pcie_ep_stop(struct pci_epc *epc)
>  {
>  	struct rcar_pcie_endpoint *ep = epc_get_drvdata(epc);
> @@ -446,6 +654,8 @@ static const struct pci_epc_features rcar_pcie_epc_features = {
>  	.bar_fixed_size[0] = 128,
>  	.bar_fixed_size[2] = 256,
>  	.bar_fixed_size[4] = 256,
> +	.internal_dmac = true,
> +	.internal_dmac_mask = DMA_BIT_MASK(32),
>  };
>  
>  static const struct pci_epc_features*
> @@ -466,6 +676,7 @@ static const struct pci_epc_ops rcar_pcie_epc_ops = {
>  	.start		= rcar_pcie_ep_start,
>  	.stop		= rcar_pcie_ep_stop,
>  	.get_features	= rcar_pcie_ep_get_features,
> +	.dmac_transfer	= rcar_pcie_ep_data_transfer,
>  };
>  
>  static const struct of_device_id rcar_pcie_ep_of_match[] = {
> @@ -480,6 +691,7 @@ static int rcar_pcie_ep_probe(struct platform_device *pdev)
>  	struct rcar_pcie_endpoint *ep;
>  	struct rcar_pcie *pcie;
>  	struct pci_epc *epc;
> +	int dmac_irq;
>  	int err;
>  
>  	ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
> @@ -502,6 +714,14 @@ static int rcar_pcie_ep_probe(struct platform_device *pdev)
>  		goto err_pm_put;
>  	}
>  
> +	dmac_irq = platform_get_irq(pdev, 1);
> +	if (dmac_irq < 0)

"err = dmac_irq" or just use "err".

Thanks,
Mani
> +		goto err_pm_put;
> +
> +	init_completion(&ep->irq_raised);
> +	mutex_init(&ep->dma_operation);
> +	spin_lock_init(&ep->lock);
> +
>  	ep->num_ib_windows = MAX_NR_INBOUND_MAPS;
>  	ep->ib_window_map =
>  			devm_kcalloc(dev, BITS_TO_LONGS(ep->num_ib_windows),
> @@ -533,6 +753,13 @@ static int rcar_pcie_ep_probe(struct platform_device *pdev)
>  
>  	rcar_pcie_ep_hw_init(pcie);
>  
> +	err = devm_request_irq(dev, dmac_irq, rcar_pcie_ep_dmac_irq_handler,
> +			       0, "pcie-rcar-ep-dmac", pcie);
> +	if (err) {
> +		dev_err(dev, "failed to request dmac irq\n");
> +		goto err_pm_put;
> +	}
> +
>  	err = pci_epc_multi_mem_init(epc, ep->ob_window, ep->num_ob_windows);
>  	if (err < 0) {
>  		dev_err(dev, "failed to initialize the epc memory space\n");
> diff --git a/drivers/pci/controller/pcie-rcar.h b/drivers/pci/controller/pcie-rcar.h
> index 9bb125db85c6..874f8a384e6d 100644
> --- a/drivers/pci/controller/pcie-rcar.h
> +++ b/drivers/pci/controller/pcie-rcar.h
> @@ -54,6 +54,29 @@
>  #define  PAR_ENABLE		BIT(31)
>  #define  IO_SPACE		BIT(8)
>  
> +/* PCIe DMAC control reg & mask */
> +#define PCIEDMAOR		0x04000
> +#define  PCIEDMAOR_DMAE		BIT(31)
> +#define  PCIEDMAOR_DMAACT	BIT(16)
> +#define PCIEDMPALR(x)		(0x04100 + ((x) * 0x40))
> +#define PCIEDMPAUR(x)		(0x04104 + ((x) * 0x40))
> +#define PCIEDMIAR(x)		(0x04108 + ((x) * 0x40))
> +#define PCIEDMBCNTR(x)		(0x04110 + ((x) * 0x40))
> +#define PCIEDMCCAR(x)		(0x04120 + ((x) * 0x40))
> +#define PCIEDMCHCR(x)		(0x04128 + ((x) * 0x40))
> +#define  PCIEDMCHCR_CHE		BIT(31)
> +#define  PCIEDMCHCR_DIR		BIT(30)
> +#define PCIEDMCHSR(x)		(0x0412c + ((x) * 0x40))
> +#define  PCIEDMCHSR_CHTCE	BIT(28)
> +#define  PCIEDMCHSR_PEEE	BIT(27)
> +#define  PCIEDMCHSR_IBEE	BIT(25)
> +#define  PCIEDMCHSR_CHTC	BIT(12)
> +#define  PCIEDMCHSR_PEE		BIT(11)
> +#define  PCIEDMCHSR_IBE		BIT(9)
> +#define  PCIEDMCHSR_IE		BIT(3)
> +#define  PCIEDMCHSR_TE		BIT(0)
> +#define PCIEDMCHC2R(x)		(0x04130 + ((x) * 0x40))
> +
>  /* Configuration */
>  #define PCICONF(x)		(0x010000 + ((x) * 0x4))
>  #define  INTDIS			BIT(10)
> -- 
> 2.25.1
>