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Message-ID: <3e5ea70d-805a-ff30-663b-e802d9116a49@kaod.org>
Date:   Mon, 4 Apr 2022 09:11:33 +0200
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Subject: Re: [PATCH v4 04/11] spi: aspeed: Add support for direct mapping
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To:     Pratyush Yadav <p.yadav@ti.com>
CC:     <linux-spi@vger.kernel.org>, <linux-mtd@lists.infradead.org>,
        Mark Brown <broonie@kernel.org>,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        <linux-aspeed@lists.ozlabs.org>, Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>,
        <devicetree@vger.kernel.org>, Rob Herring <robh+dt@kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, Tao Ren <rentao.bupt@gmail.com>
References: <20220325100849.2019209-1-clg@kaod.org>
 <20220325100849.2019209-5-clg@kaod.org>
 <20220330194548.zldbkaoctlhgwcl2@ti.com>
From:   =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@kaod.org>
In-Reply-To: <20220330194548.zldbkaoctlhgwcl2@ti.com>
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Precedence: bulk

On 3/30/22 21:45, Pratyush Yadav wrote:
> 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@jms.id.au>
>> Tested-by: Joel Stanley <joel@jms.id.au>
>> Tested-by: Tao Ren <rentao.bupt@gmail.com>
>> Signed-off-by: Cédric Le Goater <clg@kaod.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.

It's only a small optimization for startup when the SFDP probing is done.
There are quite a few reads which are large :

   spi-aspeed-smc 1e630000.spi: CE0 read OP 0x5a mode:1.1.1.1 naddr:0x3 ndummies:0x1 len:0x10
   spi-aspeed-smc 1e630000.spi: CE0 read OP 0x5a mode:1.1.1.1 naddr:0x3 ndummies:0x1 len:0x10
   spi-aspeed-smc 1e630000.spi: CE0 read OP 0x5a mode:1.1.1.1 naddr:0x3 ndummies:0x1 len:0x120
   spi-aspeed-smc 1e630000.spi: CE0 read OP 0x5a mode:1.1.1.1 naddr:0x3 ndummies:0x1 len:0x40
   spi-aspeed-smc 1e630000.spi: CE0 read OP 0x5a mode:1.1.1.1 naddr:0x3 ndummies:0x1 len:0x8

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

OK. I understand. It's not a problem as it works either way.

Thanks,

C.


>>   	} 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
>>
>