Date:   Thu, 31 Mar 2022 01:15:48 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Cédric Le Goater <clg@...d.org>
CC:     <linux-spi@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        Mark Brown <broonie@...nel.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-aspeed@...ts.ozlabs.org>, Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>,
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Tao Ren <rentao.bupt@...il.com>
Subject: Re: [PATCH v4 04/11] spi: aspeed: Add support for direct mapping

On 25/03/22 11:08AM, Cédric Le Goater wrote:
> Use direct mapping to read the flash device contents. This operation
> mode is called "Command mode" on Aspeed SoC SMC controllers. It uses a
> Control Register for the settings to apply when a memory operation is
> performed on the flash device mapping window.
> 
> If the window is not big enough, fall back to the "User mode" to
> perform the read.
> 
> Since direct mapping now handles all reads of the flash device
> contents, also use memcpy_fromio for other address spaces, such as
> SFDP.
> 
> Direct mapping for writes will come later when validated.
> 
> Reviewed-by: Joel Stanley <joel@....id.au>
> Tested-by: Joel Stanley <joel@....id.au>
> Tested-by: Tao Ren <rentao.bupt@...il.com>
> Signed-off-by: Cédric Le Goater <clg@...d.org>
> ---
>  drivers/spi/spi-aspeed-smc.c | 67 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 65 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-aspeed-smc.c b/drivers/spi/spi-aspeed-smc.c
> index 997ec2e45118..0951766baef4 100644
> --- a/drivers/spi/spi-aspeed-smc.c
> +++ b/drivers/spi/spi-aspeed-smc.c
> @@ -322,8 +322,8 @@ static int do_aspeed_spi_exec_op(struct spi_mem *mem, const struct spi_mem_op *o
>  		if (!op->addr.nbytes)
>  			ret = aspeed_spi_read_reg(chip, op);
>  		else
> -			ret = aspeed_spi_read_user(chip, op, op->addr.val,
> -						   op->data.nbytes, op->data.buf.in);
> +			memcpy_fromio(op->data.buf.in, chip->ahb_base + op->addr.val,
> +				      op->data.nbytes);

I think I commented on this earlier too, though I failed to respond to 
your reply. Let me bring the topic back up. I think this can cause an 
invalid memory address to be accessed. Not all SPI MEM consumers will 
use dirmap APIs, and they won't use them all the time. For example, SPI 
NOR can perform some operations to reset the flash before shutting down. 
For example, SPI NOR turns off 4byte address mode during shutdown. This 
will be a register read/write operation, which usually has a different 
opcode.

So I think you should keep dirmap and exec_op() independent of each 
other.

>  	} else {
>  		if (!op->addr.nbytes)
>  			ret = aspeed_spi_write_reg(chip, op);
> @@ -403,10 +403,73 @@ static int aspeed_spi_chip_set_default_window(struct aspeed_spi_chip *chip)
>  	return chip->ahb_window_size ? 0 : -1;
>  }
>  
> +static int aspeed_spi_dirmap_create(struct spi_mem_dirmap_desc *desc)
> +{
> +	struct aspeed_spi *aspi = spi_controller_get_devdata(desc->mem->spi->master);
> +	struct aspeed_spi_chip *chip = &aspi->chips[desc->mem->spi->chip_select];
> +	struct spi_mem_op *op = &desc->info.op_tmpl;
> +	u32 ctl_val;
> +	int ret = 0;
> +
> +	chip->clk_freq = desc->mem->spi->max_speed_hz;
> +
> +	/* Only for reads */
> +	if (op->data.dir != SPI_MEM_DATA_IN)
> +		return -EOPNOTSUPP;
> +
> +	if (desc->info.length > chip->ahb_window_size)
> +		dev_warn(aspi->dev, "CE%d window (%dMB) too small for mapping",
> +			 chip->cs, chip->ahb_window_size >> 20);
> +
> +	/* Define the default IO read settings */
> +	ctl_val = readl(chip->ctl) & ~CTRL_IO_CMD_MASK;
> +	ctl_val |= aspeed_spi_get_io_mode(op) |
> +		op->cmd.opcode << CTRL_COMMAND_SHIFT |
> +		CTRL_IO_DUMMY_SET(op->dummy.nbytes / op->dummy.buswidth) |
> +		CTRL_IO_MODE_READ;
> +
> +	/* Tune 4BYTE address mode */
> +	if (op->addr.nbytes) {
> +		u32 addr_mode = readl(aspi->regs + CE_CTRL_REG);
> +
> +		if (op->addr.nbytes == 4)
> +			addr_mode |= (0x11 << chip->cs);
> +		else
> +			addr_mode &= ~(0x11 << chip->cs);
> +		writel(addr_mode, aspi->regs + CE_CTRL_REG);
> +	}
> +
> +	/* READ mode is the controller default setting */
> +	chip->ctl_val[ASPEED_SPI_READ] = ctl_val;
> +	writel(chip->ctl_val[ASPEED_SPI_READ], chip->ctl);
> +
> +	dev_info(aspi->dev, "CE%d read buswidth:%d [0x%08x]\n",
> +		 chip->cs, op->data.buswidth, chip->ctl_val[ASPEED_SPI_READ]);
> +
> +	return ret;
> +}
> +
> +static ssize_t aspeed_spi_dirmap_read(struct spi_mem_dirmap_desc *desc,
> +				      u64 offset, size_t len, void *buf)
> +{
> +	struct aspeed_spi *aspi = spi_controller_get_devdata(desc->mem->spi->master);
> +	struct aspeed_spi_chip *chip = &aspi->chips[desc->mem->spi->chip_select];
> +
> +	/* Switch to USER command mode if mapping window is too small */
> +	if (chip->ahb_window_size < offset + len)
> +		aspeed_spi_read_user(chip, &desc->info.op_tmpl, offset, len, buf);
> +	else
> +		memcpy_fromio(buf, chip->ahb_base + offset, len);
> +
> +	return len;
> +}
> +
>  static const struct spi_controller_mem_ops aspeed_spi_mem_ops = {
>  	.supports_op = aspeed_spi_supports_op,
>  	.exec_op = aspeed_spi_exec_op,
>  	.get_name = aspeed_spi_get_name,
> +	.dirmap_create = aspeed_spi_dirmap_create,
> +	.dirmap_read = aspeed_spi_dirmap_read,
>  };
>  
>  static void aspeed_spi_chip_set_type(struct aspeed_spi *aspi, unsigned int cs, int type)
> -- 
> 2.34.1
> 

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

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