Hi Simon,
I re-phrase all the question from previous thread and continue in this
for more discussion on spi-nor development.
> Is it intended that SPI flash should be a driver for the MTD uclass?
> Others would be NAND and CFI. From what I can tell MTD has the same
> operations as SPI flash (erase, read, write) and adds a lot more.
>
> Or is SPI flash really a separate uclass from MTD, with SPI flash
> being at a higher level?
Based on my "sf: MTD support" series SPI flash is a separate uclass from
MTD and it uses mtd_info operations.
>> cmd_sf
>> =======
>> MTD
>> =======
>> spi-nor or spi-flash
>> ===============
>> "spi-nor to spi drivers" and spi-nor controller driver
>> =======================================
> Your diagram above suggests that MTD calls into SPI NOR or SPI flash,
> but when I look at (for exampe) spi_flash_erase(), it is calling
> mtd_erase(), suggesting that it is above MTD in the software stack,
> the opposite of your diagram above.
>
Will explain this clearly in below description.
> Conceptually this seems problematic.
>
> SPI flash is a uclass and supports driver model. It has operations,
> etc. Your patches remove the operations in favour of calling MTD. But
> MTD does not support driver model. This is getting really messy.
>
Will explain this clearly in below description.
Introducing SPI-NOR:
********************
Some of the spi drivers or spi controllers at drivers/spi/*
not a real spi controllers, unlike normal spi controllers
those operates varienty of spi devices among spi-nor flash is
one of them but instead these were specially designed for
to operate spi-nor flash devices - these are spi-nor controllers.
example: drivers/spi/fsl_qspi.c
The problem with these were sitting at drivers/spi is entire
spi layer becomes spi-nor flash oriented which is absolutely
wrong indication where spi layer gets effected more with
flash operations - So this SPI-NOR will resolve this issue
by separating all spi-nor flash operations from spi layer
and by creating a generic layer called SPI-NOR core where it
deals with all SPI-NOR flash activities. The basic idea is
taken from Linux spi-nor framework.
SPI-NOR Block diagram:
*********************
=========
cmd_sf.c
===========
spi_flash.h
===========
mtdcore.c
===========
spi-nor.c
========================
m25p80.c fsl_qspi.c
========== ===========
spi-uclass spi-nor hw
========== ===========
spi_drivers
===========
spi-bus hw
==========
Note:
- spi-nor.c is a common core for m25p80.c which is a spi-nor to spi
driver interface layer and for fsl_qspi.c which is a typical spi-nor
controller driver.
- Challenging task is about probe.
SPI-NOR Development plan:
*************************
a) Adding MTD core support:
From command point of view the spi-flash is like a mtd device
having erase/write/read ops with offset, addr and size, but from lower
layers the spi-flash becomes either spi-nor or spi-nand so they have
their own specific features like struct spi_nor {}.
This is the reason for calling MTD from command layer and the lower
layer as SPI_NOR uclass.
b) Drop spi_flash uclass:
Since spi_flash is a generic term for serial flash devices among
these spi-nor and spi-nand are the real device categories so add
driver model to these categories.
I sent the series [1] for above a) and b)
c) Add spi-nor support (mean Adding SPI-NOR dm drivers) the next step.
Detailed SPI-NOR with examples:
******************************
include/spi_flash.h
-------------------
struct spi_flash {
struct spi_nor *nor;
};
include/linux/mtd/spi-nor.h
---------------------------
struct spi_nor {
struct udevice *dev;
struct mtd_info *info;
// spi-nor hooks
int (*read_reg)(struct udevice *dev, u8 cmd, u8 *val, int len);
int (*write_reg)(struct udevice *dev, u8 cmd, u8 *data, int len);
int (*read_mmap)(struct udevice *dev, void *data, void *offset,
size_t len);
int (*read)(struct udevice *dev, const u8 *opcode, size_t cmd_len,
void *data, size_t data_len);
int (*write)(struct udevice *dev, const u8 *cmd, size_t cmd_len,
const void *data, size_t data_len);
};
drivers/mtd/spi-nor/spi-nor.c
-----------------------------
static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
{
// call to spi-nor erase nor->erase()
}
static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, u_char *buf)
{
// call to spi-nor erase nor->read()
}
static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf)
{
// call to spi-nor erase nor->erase()
}
int spi_nor_scan(struct spi_nor *nor)
{
struct mtd_info *mtd = nor->mtd;
// read_jedec
// assign mtd hooks
// other spi-nor stuff
}
drivers/mtd/spi-nor/m25p80.c
----------------------------
struct m25p80 {
struct spi_slave *spi;
struct mtd_info mtd;
};
static int m25p80_probe(struct udevice *dev)
{
struct spi_slave *spi = dev_get_parentdata(dev);
struct spi_nor *nor = dev_get_uclass_priv(dev);
struct m25p80 *flash = dev_get_priv(dev);
struct spi_flash *sflash;
spi_nor_scan(nor);
add_mtd_device(&flash->mtd);
}
// spi-nor hooks
static const struct dm_spi_flash_ops m25p80_ops = {
.read = m25p80_read,
.write = m25p80_write,
.erase = m25p80_erase,
};
static const struct udevice_id m25p80_ids[] = {
{ .compatible = "jedec,spi-nor" },
{ }
};
U_BOOT_DRIVER(m25p80) = {
.name = "m25p80",
.id = UCLASS_SPI_NOR,
.of_match = m25p80_ids,
.probe = m25p80_probe,
.priv_auto_alloc_size = sizeof(struct m25p80),
.ops = &m25p80_ops,
};
drivers/mtd/spi-nor/fsl-qspi.c
------------------------------
struct fsl_qspi {
struct mtd_info mtd;
};
static int fsl_probe(struct udevice *dev)
{
struct spi_nor *nor = dev_get_uclass_priv(dev);
struct fsl_qspi *q = dev_get_priv(dev);
struct spi_flash *sflash;
spi_nor_scan(nor);
add_mtd_device(&q->mtd);
}
// spi-nor hooks
static const struct dm_spi_nor_ops fsl_qspi_ops = {
.read = fsl_qspi_read,
.write = fsl_qspi_write,
.erase = fsl_qspi_erase,
};
static const struct udevice_id fsl_qspi_ids[] = {
{ .compatible = "fsl,vf610-qspi" },
{ }
};
U_BOOT_DRIVER(fsl_qspi) = {
.name = "fsl_qspi",
.id = UCLASS_SPI_NOR,
.of_match = fsl_qspi_ids,
.probe = fsl_qspi_probe,
.priv_auto_alloc_size = sizeof(struct fsl_qspi),
ops = &fsl_qspi_ops,
};
About non-dm handling
*********************
We still maintain the driver similar to m25p80.c for non-dm interface
till all spi-drivers converted into dm.
[1] https://www.mail-archive.com/[email protected]/msg193802.html
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