Re: [PATCH v4 8/9] nand: spi: Add generic SPI controller support

Cyrille Pitchen
2017-03-29T21:38:33Z

Hi Peter,

Le 23/03/2017 à 10:43, Peter Pan a écrit :
> This commit supports to use generic spi controller
> as spi nand controller.
>
> Signed-off-by: Peter Pan <peterpandong@micron.com>
> ---
> drivers/mtd/nand/spi/Kconfig | 2 +
> drivers/mtd/nand/spi/Makefile | 1 +
> drivers/mtd/nand/spi/controllers/Kconfig | 5 +
> drivers/mtd/nand/spi/controllers/Makefile | 1 +
> drivers/mtd/nand/spi/controllers/generic-spi.c | 150 +++++++++++++++++++++++++
> 5 files changed, 159 insertions(+)
> create mode 100644 drivers/mtd/nand/spi/controllers/Kconfig
> create mode 100644 drivers/mtd/nand/spi/controllers/Makefile
> create mode 100644 drivers/mtd/nand/spi/controllers/generic-spi.c
>
> diff --git a/drivers/mtd/nand/spi/Kconfig b/drivers/mtd/nand/spi/Kconfig
> index d77c46e..6bd1c65 100644
> --- a/drivers/mtd/nand/spi/Kconfig
> +++ b/drivers/mtd/nand/spi/Kconfig
> @@ -3,3 +3,5 @@ menuconfig MTD_SPI_NAND
> depends on MTD_NAND
> help
> This is the framework for the SPI NAND device drivers.
> +
> +source "drivers/mtd/nand/spi/controllers/Kconfig"
> diff --git a/drivers/mtd/nand/spi/Makefile b/drivers/mtd/nand/spi/Makefile
> index db0b91b..6ad5f24 100644
> --- a/drivers/mtd/nand/spi/Makefile
> +++ b/drivers/mtd/nand/spi/Makefile
> @@ -1,3 +1,4 @@
> obj-$(CONFIG_MTD_SPI_NAND) += core.o
> obj-$(CONFIG_MTD_SPI_NAND) += manufactures.o
> obj-$(CONFIG_MTD_SPI_NAND) += micron.o
> +obj-$(CONFIG_MTD_SPI_NAND) += controllers/
> diff --git a/drivers/mtd/nand/spi/controllers/Kconfig b/drivers/mtd/nand/spi/controllers/Kconfig
> new file mode 100644
> index 0000000..8ab7023
> --- /dev/null
> +++ b/drivers/mtd/nand/spi/controllers/Kconfig
> @@ -0,0 +1,5 @@
> +config GENERIC_SPI_NAND
> + tristate "SPI NAND with generic SPI bus Support"
> + depends on MTD_SPI_NAND && SPI
> + help
> + This is to support SPI NAND device with generic SPI bus.
> diff --git a/drivers/mtd/nand/spi/controllers/Makefile b/drivers/mtd/nand/spi/controllers/Makefile
> new file mode 100644
> index 0000000..46cbf29
> --- /dev/null
> +++ b/drivers/mtd/nand/spi/controllers/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_GENERIC_SPI_NAND) += generic-spi.o
> diff --git a/drivers/mtd/nand/spi/controllers/generic-spi.c b/drivers/mtd/nand/spi/controllers/generic-spi.c
> new file mode 100644
> index 0000000..da1f224
> --- /dev/null
> +++ b/drivers/mtd/nand/spi/controllers/generic-spi.c
> @@ -0,0 +1,150 @@
> +/*
> + * Copyright (c) 2009-2017 Micron Technology, Inc.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/mtd/spinand.h>
> +
> +struct gen_spi_spinand_controller {
> + struct spinand_controller ctrl;
> + struct spi_device *spi;
> +};
> +
> +#define to_gen_spi_spinand_controller(c) \
> + container_of(c, struct gen_spi_spinand_controller, ctrl)
> +
> +/*
> + * gen_spi_spinand_exec_op - to process a command to send to the
> + * SPI NAND by generic SPI bus
> + * @chip: SPI NAND device structure
> + * @op: SPI NAND operation descriptor
> + */
> +static int gen_spi_spinand_exec_op(struct spinand_device *chip,
> + struct spinand_op *op)
> +{
> + struct spi_message message;
> + struct spi_transfer x[3];
> + struct spinand_controller *scontroller = chip->controller.controller;
> + struct gen_spi_spinand_controller *controller;
> +
> + controller = to_gen_spi_spinand_controller(scontroller);
> + spi_message_init(&message);
> + memset(x, 0, sizeof(x));
> + x[0].len = 1;
> + x[0].tx_nbits = 1;
> + x[0].tx_buf = &op->cmd;
> + spi_message_add_tail(&x[0], &message);
> +
> + if (op->n_addr + op->dummy_bytes) {
> + x[1].len = op->n_addr + op->dummy_bytes;
> + x[1].tx_nbits = op->addr_nbits;
> + x[1].tx_buf = op->addr;
> + spi_message_add_tail(&x[1], &message);
> + }
> + if (op->n_tx) {
> + x[2].len = op->n_tx;
> + x[2].tx_nbits = op->data_nbits;
> + x[2].tx_buf = op->tx_buf;
> + spi_message_add_tail(&x[2], &message);
> + } else if (op->n_rx) {
> + x[2].len = op->n_rx;
> + x[2].rx_nbits = op->data_nbits;
> + x[2].rx_buf = op->rx_buf;
> + spi_message_add_tail(&x[2], &message);
> + }
> + return spi_sync(controller->spi, &message);
> +}

2 comments:

1/
maybe you can merge 'struct spi_transfer' in some cases:

for instance with SPI x-x-z protocols, you can carry both the
instruction and address/dummy bytes in a single spi_transfer structure.

Also for Read operations (not applicable for Write/Page Program), with
SPI x-z-z, you can merge both the address/dummy and data bytes in a
single spi_transfer structure.

This could speed-up the operation with some SPI controller drivers.
However this is just an optimization otherwise it should work as is.

2/
Some spi controller drivers, like the TI QSPI controller driver, may
want to use something similar to the spi_flash_read() function used from
drivers/mtd/spi-nor/m25p80.c.

Indeed, some QSPI controllers can speed up read operations by mapping
the flash data array into the system memory. In such a case, the regular
SPI API (spi_message and spi_transfer structures) is no longer used.
That's why spi_flash_read() was introduced.

However unlike SPI-NOR memories, SPI-NAND memories require to read data
in 2 steps: internal data array -> internal cache then internal cache ->
SPI bus. Hence using a mapping in the system memory only for "read from
cache" operations is likely less interesting than reading the whole data
array like regular memory as we can do with SPI NOR.

This is another optimization, so not mandatory at all, but I just wanted
to warn you about that so be prepared to be queried about that ;)

> +
> +static struct spinand_controller_ops gen_spi_spinand_ops = {
> + .exec_op = gen_spi_spinand_exec_op,
> +};
> +
> +static int gen_spi_spinand_probe(struct spi_device *spi)
> +{
> + struct spinand_device *chip;
> + struct gen_spi_spinand_controller *controller;
> + struct spinand_controller *spinand_controller;
> + int ret;
> + u32 max_speed_hz = spi->max_speed_hz;
> +
> + chip = spinand_alloc(&spi->dev);
> + if (IS_ERR(chip)) {
> + ret = PTR_ERR(chip);
> + goto err1;
> + }
> + controller = kzalloc(sizeof(*controller), GFP_KERNEL);
> + if (!controller) {
> + ret = -ENOMEM;
> + goto err2;
> + }
> + controller->spi = spi;
> + spinand_controller = &controller->ctrl;
> + spinand_controller->ops = &gen_spi_spinand_ops;
> + spinand_controller->caps = SPINAND_CAP_RD_X1 | SPINAND_CAP_WR_X1;
> + if (spi->mode & SPI_RX_QUAD)
> + spinand_controller->caps |= SPINAND_CAP_RD_QUAD |
> + SPINAND_CAP_RD_X4;
> + if (spi->mode & SPI_RX_DUAL)
> + spinand_controller->caps |= SPINAND_CAP_RD_DUAL |
> + SPINAND_CAP_RD_X2;
> + if (spi->mode & SPI_TX_QUAD)
> + spinand_controller->caps |= SPINAND_CAP_WR_QUAD |
> + SPINAND_CAP_WR_X4;
> + if (spi->mode & SPI_TX_DUAL)
> + spinand_controller->caps |= SPINAND_CAP_WR_DUAL |
> + SPINAND_CAP_WR_X2;

I think this is wrong:
the SPI_RX_QUAD means the controller can receive data on 4 I/O line
hence it allows SPINAND_CAP_RD_X4 (1-1-4) but not necessarily
SPINAND_CAP_QUAD (1-4-4).

To add SPINAND_CAP_QUAD (1-4-4), SPINAND_CAP_WR_X4 (1-1-4) and
SPINAND_CAP_WR_QUAD (1-4-4) you need both SPI_RX_QUAD and SPI_TX_QUAD.

So with Dual SPI protocols:

at least SPI_RX_DUAL: caps = RD_X2
both SPI_RX_DUAL and SPI_TX_DUAL: caps |= (RD_DUAL | WR_X2 | WR_DUAL);

SPI masters (controllers) are not aware of SPI x-y-z flash protocols,
they just claim they can use more than 1 I/O line to read data and/or
more than 1 I/0 line to write data.

> + chip->controller.controller = spinand_controller;
> + spi_set_drvdata(spi, chip);
> + spi->max_speed_hz = min_t(int, 25000000, max_speed_hz);
> +
> + ret = spinand_register(chip);
> + if (ret)
> + goto err3;
> +
> + spi->max_speed_hz = max_speed_hz;
> +
> + return 0;
> +
> +err3:
> + kfree(controller);
> +err2:
> + spinand_free(chip);
> +err1:
> + return ret;
> +}
> +
> +static int gen_spi_spinand_remove(struct spi_device *spi)
> +{
> + struct spinand_device *chip = spi_get_drvdata(spi);
> +
> + spinand_unregister(chip);
> + kfree(to_gen_spi_spinand_controller(chip->controller.controller));
> + spinand_free(chip);
> +
> + return 0;
> +}
> +
> +static struct spi_driver gen_spi_spinand_driver = {
> + .driver = {
> + .name = "generic_spinand",
> + .owner = THIS_MODULE,
> + },
> + .probe = gen_spi_spinand_probe,
> + .remove = gen_spi_spinand_remove,
> +};
> +module_spi_driver(gen_spi_spinand_driver);
> +
> +MODULE_DESCRIPTION("Generic SPI controller to support SPI NAND");
> +MODULE_AUTHOR("Peter Pan<peterpandong@micron.com>");
> +MODULE_LICENSE("GPL v2");
>