[U-Boot] dm: Introduce SPI-NOR framework
Jagan Teki
jteki at openedev.com
Tue Dec 8 16:36:02 CET 2015
Hi Simon,
On 8 December 2015 at 08:22, Simon Glass <sjg at chromium.org> wrote:
> Hi Jagan,
>
> On 3 December 2015 at 03:10, Jagan Teki <jteki at openedev.com> wrote:
>> 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)
>
> It doesn't look like that series drops the SPI flash uclass.
Yes, I have not dropped SPI flash uclass fully on the series only ops.
>
>>
>> c) Add spi-nor support (mean Adding SPI-NOR dm drivers) the next step.
>
> I think this is what I am missing. If you are moving to SPI NOR, what
> is the API? Is it the roughly the same as the current SPI flash API?
> (read, write, erase)
For now SPI NOR api's are same as SPI flash in terms of structure
members but spi-nor hooks, definition and the calling context are
different. Usually SPI flash ops are getting called from cmd_sf ==>
spi_flash.h ==> sf-uclass.c and then finally goes into sf_ops.c for
actual function definitions, but in case of SPI NOR spi-nor ops
(defined in spi-nor controller drivers - sf_probe.c, fsl_qspi.c) are
getting called from mtd_info ops definitions which are defined at
spi-nor core (which is sf_ops.c as of now), and from cmd_sf =>
spi_flash.h => mtdcore.c and the finally goes into spi-nor for actual
mtd ops definitions.
Unlike SPI flash, SPI nor framework will separate the flow from
generic spi controller which one of the connected slave as spi nor
flash (through sf_probe.c) vs spi-nor controller drivers like
fsl_qspi.c
>
>>
>> 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);
>
> But here you show SPI nor with its own operations. So does SPI nor
> call into MTD? What is your plan to move MTD to driver model and
> create a MTD uclass? Also, does this mean that each SPI nor device
> will have an MTD sub-device?
Yes, SPI NOR is different from MTD and MTD operations which are
defined at spi-nor will call the respective spi-nor controller driver
spi-nor operations. which I explained above.
I think using MTD uclass is another approach where we can remove the
udevice from SPI NOR and making all spi-nor controller driver as
MTD_UCLASS - do you prefer this?
>
>> };
>>
>> 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/u-boot@lists.denx.de/msg193802.html
thanks!
--
Jagan.
More information about the U-Boot
mailing list