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Date:   Wed, 22 Jan 2020 09:50:20 +0100
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Kamal Dasu <kdasu.kdev@gmail.com>
Cc:     linux-mtd@lists.infradead.org,
        bcm-kernel-feedback-list@broadcom.com,
        linux-kernel@vger.kernel.org,
        Brian Norris <computersforpeace@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH V2 3/3] mtd: rawnand: brcmnand: Add support for
 flash-edu for dma transfers
Message-ID: <20200122095020.4b916f34@xps13>
In-Reply-To: <20200121200011.32296-3-kdasu.kdev@gmail.com>
References: <20200121200011.32296-1-kdasu.kdev@gmail.com>
        <20200121200011.32296-3-kdasu.kdev@gmail.com>
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Hi Kamal,

I'm fine with the patch, nitpicking below :)

Kamal Dasu <kdasu.kdev@gmail.com> wrote on Tue, 21 Jan 2020 15:00:08
-0500:

> Legacy mips soc platforms that have controller v5.0 and 6.0 use
> flash-edu block for dma transfers. This change adds support for
> nand dma transfers using the EDU block.
> 
> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> ---
>  drivers/mtd/nand/raw/brcmnand/brcmnand.c | 296 ++++++++++++++++++++++-
>  1 file changed, 290 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> index 1a66b1cd51c0..61347607f1da 100644
> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> @@ -102,6 +102,45 @@ struct brcm_nand_dma_desc {
>  #define NAND_CTRL_RDY			(INTFC_CTLR_READY | INTFC_FLASH_READY)
>  #define NAND_POLL_STATUS_TIMEOUT_MS	100
>  
> +#define EDU_CMD_WRITE          0x00
> +#define EDU_CMD_READ           0x01
> +#define EDU_STATUS_ACTIVE      BIT(0)
> +#define EDU_ERR_STATUS_ERRACK  BIT(0)
> +#define EDU_DONE_MASK		GENMASK(1, 0)
> +
> +#define EDU_CONFIG_MODE_NAND   BIT(0)
> +#define EDU_CONFIG_SWAP_BYTE   BIT(1)
> +#ifdef CONFIG_CPU_BIG_ENDIAN
> +#define EDU_CONFIG_SWAP_CFG     EDU_CONFIG_SWAP_BYTE
> +#else
> +#define EDU_CONFIG_SWAP_CFG     0
> +#endif
> +
> +/* edu registers */
> +enum edu_reg {
> +	EDU_CONFIG = 0,
> +	EDU_DRAM_ADDR,
> +	EDU_EXT_ADDR,
> +	EDU_LENGTH,
> +	EDU_CMD,
> +	EDU_STOP,
> +	EDU_STATUS,
> +	EDU_DONE,
> +	EDU_ERR_STATUS,
> +};
> +
> +static const u16  edu_regs[] = {
> +	[EDU_CONFIG] = 0x00,
> +	[EDU_DRAM_ADDR] = 0x04,
> +	[EDU_EXT_ADDR] = 0x08,
> +	[EDU_LENGTH] = 0x0c,
> +	[EDU_CMD] = 0x10,
> +	[EDU_STOP] = 0x14,
> +	[EDU_STATUS] = 0x18,
> +	[EDU_DONE] = 0x1c,
> +	[EDU_ERR_STATUS] = 0x20,
> +};

Why not defining the offsets in the enum directly?

> +
>  /* flash_dma registers */
>  enum flash_dma_reg {
>  	FLASH_DMA_REVISION = 0,
> @@ -167,6 +206,8 @@ enum {
>  	BRCMNAND_HAS_WP				= BIT(3),
>  };
>  
> +struct brcmnand_host;
> +
>  struct brcmnand_controller {
>  	struct device		*dev;
>  	struct nand_controller	controller;
> @@ -185,17 +226,32 @@ struct brcmnand_controller {
>  
>  	int			cmd_pending;
>  	bool			dma_pending;
> +	bool                    edu_pending;
>  	struct completion	done;
>  	struct completion	dma_done;
> +	struct completion       edu_done;
>  
>  	/* List of NAND hosts (one for each chip-select) */
>  	struct list_head host_list;
>  
> +	/* EDU info, per-transaction */
> +	const u16               *edu_offsets;
> +	void __iomem            *edu_base;
> +	unsigned int            edu_irq;
> +	int                     edu_count;
> +	u64                     edu_dram_addr;
> +	u32                     edu_ext_addr;
> +	u32                     edu_cmd;
> +	u32                     edu_config;
> +
>  	/* flash_dma reg */
>  	const u16		*flash_dma_offsets;
>  	struct brcm_nand_dma_desc *dma_desc;
>  	dma_addr_t		dma_pa;
>  
> +	int (*dma_trans)(struct brcmnand_host *host, u64 addr, u32 *buf,
> +			 u32 len, u8 dma_cmd);
> +
>  	/* in-memory cache of the FLASH_CACHE, used only for some commands */
>  	u8			flash_cache[FC_BYTES];
>  
> @@ -216,6 +272,7 @@ struct brcmnand_controller {
>  	u32			nand_cs_nand_xor;
>  	u32			corr_stat_threshold;
>  	u32			flash_dma_mode;
> +	u32                     flash_edu_mode;
>  	bool			pio_poll_mode;
>  };
>  
> @@ -657,6 +714,22 @@ static inline void brcmnand_write_fc(struct brcmnand_controller *ctrl,
>  	__raw_writel(val, ctrl->nand_fc + word * 4);
>  }
>  
> +static inline void edu_writel(struct brcmnand_controller *ctrl,
> +			      enum edu_reg reg, u32 val)
> +{
> +	u16 offs = ctrl->edu_offsets[reg];
> +
> +	brcmnand_writel(val, ctrl->edu_base + offs);
> +}
> +
> +static inline u32 edu_readl(struct brcmnand_controller *ctrl,
> +			    enum edu_reg reg)
> +{
> +	u16 offs = ctrl->edu_offsets[reg];
> +
> +	return brcmnand_readl(ctrl->edu_base + offs);
> +}
> +
>  static void brcmnand_clear_ecc_addr(struct brcmnand_controller *ctrl)
>  {
>  
> @@ -926,6 +999,16 @@ static inline bool has_flash_dma(struct brcmnand_controller *ctrl)
>  	return ctrl->flash_dma_base;
>  }
>  
> +static inline bool has_edu(struct brcmnand_controller *ctrl)
> +{
> +	return ctrl->edu_base;
> +}
> +
> +static inline bool use_dma(struct brcmnand_controller *ctrl)
> +{
> +	return has_flash_dma(ctrl) || has_edu(ctrl);
> +}
> +
>  static inline void disable_ctrl_irqs(struct brcmnand_controller *ctrl)
>  {
>  	if (ctrl->pio_poll_mode)
> @@ -1299,6 +1382,52 @@ static int write_oob_to_regs(struct brcmnand_controller *ctrl, int i,
>  	return tbytes;
>  }
>  
> +static void brcmnand_edu_init(struct brcmnand_controller *ctrl)
> +{
> +	/* initialize edu */
> +	edu_writel(ctrl, EDU_ERR_STATUS, 0);
> +	edu_readl(ctrl, EDU_ERR_STATUS);
> +	edu_writel(ctrl, EDU_DONE, 0);
> +	edu_writel(ctrl, EDU_DONE, 0);
> +	edu_writel(ctrl, EDU_DONE, 0);
> +	edu_writel(ctrl, EDU_DONE, 0);
> +	edu_readl(ctrl, EDU_DONE);
> +}
> +
> +/* edu irq */
> +static irqreturn_t brcmnand_edu_irq(int irq, void *data)
> +{
> +	struct brcmnand_controller *ctrl = data;
> +
> +	if (ctrl->edu_count) {
> +		ctrl->edu_count--;
> +		while (!(edu_readl(ctrl, EDU_DONE) & EDU_DONE_MASK))
> +			udelay(1);
> +		edu_writel(ctrl, EDU_DONE, 0);
> +		edu_readl(ctrl, EDU_DONE);
> +	}
> +
> +	if (ctrl->edu_count) {
> +		ctrl->edu_dram_addr += FC_BYTES;
> +		ctrl->edu_ext_addr += FC_BYTES;
> +
> +		edu_writel(ctrl, EDU_DRAM_ADDR, (u32)ctrl->edu_dram_addr);
> +		edu_readl(ctrl, EDU_DRAM_ADDR);
> +		edu_writel(ctrl, EDU_EXT_ADDR, ctrl->edu_ext_addr);
> +		edu_readl(ctrl, EDU_EXT_ADDR);
> +
> +		mb(); /* flush previous writes */
> +		edu_writel(ctrl, EDU_CMD, ctrl->edu_cmd);
> +		edu_readl(ctrl, EDU_CMD);
> +
> +		return IRQ_HANDLED;
> +	}
> +
> +	complete(&ctrl->edu_done);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static irqreturn_t brcmnand_ctlrdy_irq(int irq, void *data)
>  {
>  	struct brcmnand_controller *ctrl = data;
> @@ -1307,6 +1436,16 @@ static irqreturn_t brcmnand_ctlrdy_irq(int irq, void *data)
>  	if (ctrl->dma_pending)
>  		return IRQ_HANDLED;
>  
> +	/* check if you need to piggy back on the ctrlrdy irq */
> +	if (ctrl->edu_pending) {
> +		if (irq == ctrl->irq && ((int)ctrl->edu_irq >= 0))
> +	/* Discard interrupts while using dedicated edu irq */
> +			return IRQ_HANDLED;
> +
> +	/* no registered edu irq, call handler */
> +		return brcmnand_edu_irq(irq, data);
> +	}
> +
>  	complete(&ctrl->done);
>  	return IRQ_HANDLED;
>  }
> @@ -1644,6 +1783,83 @@ static void brcmnand_write_buf(struct nand_chip *chip, const uint8_t *buf,
>  	}
>  }
>  
> +/**
> + *  Kick EDU engine
> + */
> +static int brcmnand_edu_trans(struct brcmnand_host *host, u64 addr, u32 *buf,
> +			      u32 len, u8 cmd)
> +{
> +	struct brcmnand_controller *ctrl = host->ctrl;
> +	unsigned long timeo = msecs_to_jiffies(200);
> +	int ret = 0;
> +	int dir = (cmd == CMD_PAGE_READ ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
> +	u8 edu_cmd = (cmd == CMD_PAGE_READ ? EDU_CMD_READ : EDU_CMD_WRITE);
> +	unsigned int trans = len >> FC_SHIFT;
> +	dma_addr_t pa;
> +
> +	pa = dma_map_single(ctrl->dev, buf, len, dir);
> +	if (dma_mapping_error(ctrl->dev, pa)) {
> +		dev_err(ctrl->dev, "unable to map buffer for EDU DMA\n");
> +		return -ENOMEM;
> +	}
> +
> +	ctrl->edu_pending = true;
> +	mb(); /* flush previous writes */

I'd prefer to have the barriers right after the IO access. I don't
think it changes anything but that would ease understand what writes
are you concerned about. Also, maybe you can use non _relaxed accessors
as you usually writel/readl in raw, I don't think you actually need a
barrier in this case.

> +
> +	ctrl->edu_dram_addr = pa;
> +	ctrl->edu_ext_addr = addr;
> +	ctrl->edu_cmd = edu_cmd;
> +	ctrl->edu_count = trans;
> +
> +	edu_writel(ctrl, EDU_DRAM_ADDR, (u32)ctrl->edu_dram_addr);
> +	edu_readl(ctrl,  EDU_DRAM_ADDR);
> +	edu_writel(ctrl, EDU_EXT_ADDR, ctrl->edu_ext_addr);
> +	edu_readl(ctrl, EDU_EXT_ADDR);
> +	edu_writel(ctrl, EDU_LENGTH, FC_BYTES);
> +	edu_readl(ctrl, EDU_LENGTH);
> +
> +	/* Start edu engine */
> +	mb(); /* flush previous writes */
> +	edu_writel(ctrl, EDU_CMD, ctrl->edu_cmd);
> +	edu_readl(ctrl, EDU_CMD);
> +
> +	if (wait_for_completion_timeout(&ctrl->edu_done, timeo) <= 0) {
> +		dev_err(ctrl->dev,
> +			"timeout waiting for EDU; status %#x, error status %#x\n",
> +			edu_readl(ctrl, EDU_STATUS),
> +			edu_readl(ctrl, EDU_ERR_STATUS));
> +	}
> +
> +	dma_unmap_single(ctrl->dev, pa, len, dir);
> +
> +	/* for program page check NAND status */
> +	if (((brcmnand_read_reg(ctrl, BRCMNAND_INTFC_STATUS) &
> +	      INTFC_FLASH_STATUS) & NAND_STATUS_FAIL) &&
> +	    edu_cmd == EDU_CMD_WRITE) {
> +		dev_info(ctrl->dev, "program failed at %llx\n",
> +			 (unsigned long long)addr);
> +		ret = -EIO;
> +	}
> +
> +	/* Make sure the EDU status is clean */
> +	if (edu_readl(ctrl, EDU_STATUS) & EDU_STATUS_ACTIVE)
> +		dev_warn(ctrl->dev, "EDU still active: %#x\n",
> +			 edu_readl(ctrl, EDU_STATUS));
> +
> +	if (unlikely(edu_readl(ctrl, EDU_ERR_STATUS) & EDU_ERR_STATUS_ERRACK)) {
> +		dev_warn(ctrl->dev, "EDU RBUS error at addr %llx\n",
> +			 (unsigned long long)addr);
> +		ret = -EIO;
> +	}
> +
> +	ctrl->edu_pending = false;
> +	brcmnand_edu_init(ctrl);
> +	edu_writel(ctrl, EDU_STOP, 0); /* force stop */
> +	edu_readl(ctrl, EDU_STOP);
> +
> +	return ret;
> +}
> +
>  /**
>   * Construct a FLASH_DMA descriptor as part of a linked list. You must know the
>   * following ahead of time:
> @@ -1850,9 +2066,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
>  try_dmaread:
>  	brcmnand_clear_ecc_addr(ctrl);
>  
> -	if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
> -		err = brcmnand_dma_trans(host, addr, buf, trans * FC_BYTES,
> -					     CMD_PAGE_READ);
> +	if (ctrl->dma_trans && !oob && flash_dma_buf_ok(buf)) {
> +		err = ctrl->dma_trans(host, addr, buf,
> +				      trans * FC_BYTES,
> +				      CMD_PAGE_READ);
> +
>  		if (err) {
>  			if (mtd_is_bitflip_or_eccerr(err))
>  				err_addr = addr;
> @@ -1988,10 +2206,12 @@ static int brcmnand_write(struct mtd_info *mtd, struct nand_chip *chip,
>  	for (i = 0; i < ctrl->max_oob; i += 4)
>  		oob_reg_write(ctrl, i, 0xffffffff);
>  
> -	if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
> -		if (brcmnand_dma_trans(host, addr, (u32 *)buf,
> -					mtd->writesize, CMD_PROGRAM_PAGE))
> +	if (use_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
> +		if (ctrl->dma_trans(host, addr, (u32 *)buf, mtd->writesize,
> +				    CMD_PROGRAM_PAGE))
> +
>  			ret = -EIO;
> +
>  		goto out;
>  	}
>  
> @@ -2494,6 +2714,8 @@ static int brcmnand_suspend(struct device *dev)
>  
>  	if (has_flash_dma(ctrl))
>  		ctrl->flash_dma_mode = flash_dma_readl(ctrl, FLASH_DMA_MODE);
> +	else if (has_edu(ctrl))
> +		ctrl->edu_config = edu_readl(ctrl, EDU_CONFIG);
>  
>  	return 0;
>  }
> @@ -2508,6 +2730,14 @@ static int brcmnand_resume(struct device *dev)
>  		flash_dma_writel(ctrl, FLASH_DMA_ERROR_STATUS, 0);
>  	}
>  
> +	if (has_edu(ctrl))
> +		ctrl->edu_config = edu_readl(ctrl, EDU_CONFIG);
> +	else {
> +		edu_writel(ctrl, EDU_CONFIG, ctrl->edu_config);
> +		edu_readl(ctrl, EDU_CONFIG);
> +		brcmnand_edu_init(ctrl);
> +	}
> +
>  	brcmnand_write_reg(ctrl, BRCMNAND_CS_SELECT, ctrl->nand_cs_nand_select);
>  	brcmnand_write_reg(ctrl, BRCMNAND_CS_XOR, ctrl->nand_cs_nand_xor);
>  	brcmnand_write_reg(ctrl, BRCMNAND_CORR_THRESHOLD,
> @@ -2553,6 +2783,52 @@ MODULE_DEVICE_TABLE(of, brcmnand_of_match);
>  /***********************************************************************
>   * Platform driver setup (per controller)
>   ***********************************************************************/
> +static int brcmnand_edu_setup(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct brcmnand_controller *ctrl = dev_get_drvdata(&pdev->dev);
> +	struct resource *res;
> +	int ret;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "flash-edu");
> +	if (res) {
> +		ctrl->edu_base = devm_ioremap_resource(dev, res);
> +		if (IS_ERR(ctrl->edu_base))
> +			return PTR_ERR(ctrl->edu_base);
> +
> +		ctrl->edu_offsets = edu_regs;
> +
> +		edu_writel(ctrl, EDU_CONFIG, EDU_CONFIG_MODE_NAND |
> +			   EDU_CONFIG_SWAP_CFG);
> +		edu_readl(ctrl, EDU_CONFIG);
> +
> +		/* initialize edu */
> +		brcmnand_edu_init(ctrl);
> +
> +		ctrl->edu_irq = platform_get_irq_optional(pdev, 1);
> +		if ((int)ctrl->edu_irq < 0) {

Why not declaring it as an int directly? I think it's preferred.

> +			dev_warn(dev,
> +				 "FLASH EDU enabled, using ctlrdy irq\n");
> +		} else {
> +			ret = devm_request_irq(dev, ctrl->edu_irq,
> +					       brcmnand_edu_irq, 0,
> +					       "brcmnand-edu", ctrl);
> +			if (ret < 0) {
> +				dev_err(ctrl->dev, "can't allocate IRQ %d: error %d\n",
> +					ctrl->edu_irq, ret);
> +				return ret;
> +			}
> +
> +			dev_info(dev, "FLASH EDU enabled using irq %u\n",
> +				 ctrl->edu_irq);
> +		}
> +
> +		/* set the appropriate edu transfer function to call */
> +		ctrl->dma_trans = brcmnand_edu_trans;
> +	}
> +
> +	return 0;
> +}
>  
>  int brcmnand_probe(struct platform_device *pdev, struct brcmnand_soc *soc)
>  {
> @@ -2578,6 +2854,7 @@ int brcmnand_probe(struct platform_device *pdev, struct brcmnand_soc *soc)
>  
>  	init_completion(&ctrl->done);
>  	init_completion(&ctrl->dma_done);
> +	init_completion(&ctrl->edu_done);
>  	nand_controller_init(&ctrl->controller);
>  	ctrl->controller.ops = &brcmnand_controller_ops;
>  	INIT_LIST_HEAD(&ctrl->host_list);
> @@ -2623,6 +2900,7 @@ int brcmnand_probe(struct platform_device *pdev, struct brcmnand_soc *soc)
>  				ctrl->reg_offsets[BRCMNAND_FC_BASE];
>  	}
>  
> +	ctrl->dma_trans = NULL;
>  	/* FLASH_DMA */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "flash-dma");
>  	if (res) {
> @@ -2665,6 +2943,12 @@ int brcmnand_probe(struct platform_device *pdev, struct brcmnand_soc *soc)
>  		}
>  
>  		dev_info(dev, "enabling FLASH_DMA\n");
> +		/* set the appropriate flash dma transfer function to call */
> +		ctrl->dma_trans = brcmnand_dma_trans;
> +	} else	{
> +		ret = brcmnand_edu_setup(pdev);
> +		if (ret < 0)
> +			goto err;

Nitpicking: you could drop the initialization of dma_trans to NULL and
assign ctrl->dma_trans in both cases of this if/else block (by moving
it out of the brcmnand_edu_setup()). I think it enhances readability.

>  	}
>  
>  	/* Disable automatic device ID config, direct addressing */


Thanks,
Miquèl