Hi Masahiro,

On 3 October 2014 07:04, Masahiro Yamada yamada.m@jp.panasonic.com wrote:

Simon,

I am totally being confused.

As far as I looked at the dm code, the private data is calloc'ed in device_probe() function

    if (drv->priv_auto_alloc_size) {
            dev->priv = calloc(1, drv->priv_auto_alloc_size);
            if (!dev->priv) {
                    ret = -ENOMEM;
                    goto fail;
            }
    }

So, dev->priv is storing the address of the allocated memory.

Am I understanding correctly?

Yes, it always does in driver model. This driver is no different.

BTW the ns16550 driver is probably the oddest in U-Boot - it looks like UniPhier has its own UART driver so it would be better to convert that I think. See below for ideas on other UART drivers to look at which are much more normal.

If so, I can't understand the following code:

static int ns16550_serial_getc(struct udevice *dev) { struct NS16550 *const com_port = dev_get_priv(dev);

    if (!serial_in(&com_port->lsr) & UART_LSR_DR)
            return -EAGAIN;

"com_port" is dev->priv, so it is pointing to the allocated area on RAM, I guess.

It looks like serial_in(&com_port->lsr) is trying to read from the hardware register ?

Or reading from malloc area RAM ??

If you go one level deeper you will see that serial_in() is defined at the top in about 5 ways, one of which is used for driver model:

#define serial_in(addr) \ ns16550_readb(com_port, addr - (unsigned char *)com_port)

So it used com_port which is not an parameter. The parameter addr is only used to specify the register. This is actually the same as the non-DM code except in that case the parameter specifies the register and hardware address at the same time.

This is done since the internal NS16550_t type is unfortunately exported all over U-Boot. This is annoying because it is actually an internal register format for the UART. Even worse is the fact that the structure changes depending on CONFIG_SYS_NS16550_REG_SIZE. We can't have this sort of thing in driver model - we need to be able to cope with the device tree specifying all the information that the UART needs. So for driver model:

/* * For driver model we always use one byte per register, and sort out the * differences in the driver */ #define CONFIG_SYS_NS16550_REG_SIZE (-1)

(see ns16550.h header for where this is used)

I would like to avoid having that type exported and use a different method to pass the UART information around. But it is used in about 30 places . So this approach allows us to move forward bit by bit, without duplicating the UART driver and creating a maintenance headache.

In terns of implementing a new UART driver, are you using device tree?

If so then you should just be able to follow along with Tegra - it's really easy - just copy that serial_tegra.c and adjust the device tree compat string and input clock. Other examples are serial_omap and serial_dw. (See u-boot-dm/working)

If you are using platform data, then the examples are serial_mxc and serial_pl01x.

Regards, Simon

Hi Masahiro,

On 4 October 2014 06:57, Masahiro YAMADA yamada.m@jp.panasonic.com wrote:

Hi Simon,

2014-10-03 22:51 GMT+09:00 Simon Glass sjg@chromium.org:

...

Hi Masahiro,

On 3 October 2014 07:04, Masahiro Yamada yamada.m@jp.panasonic.com wrote:

...

Simon,

I am totally being confused.

As far as I looked at the dm code, the private data is calloc'ed in device_probe() function

    if (drv->priv_auto_alloc_size) {
            dev->priv = calloc(1, drv->priv_auto_alloc_size);
            if (!dev->priv) {
                    ret = -ENOMEM;
                    goto fail;
            }
    }

So, dev->priv is storing the address of the allocated memory.

Am I understanding correctly?

Yes, it always does in driver model. This driver is no different.

BTW the ns16550 driver is probably the oddest in U-Boot - it looks like UniPhier has its own UART driver so it would be better to convert that I think. See below for ideas on other UART drivers to look at which are much more normal.

...

If so, I can't understand the following code:

static int ns16550_serial_getc(struct udevice *dev) { struct NS16550 *const com_port = dev_get_priv(dev);

    if (!serial_in(&com_port->lsr) & UART_LSR_DR)
            return -EAGAIN;

"com_port" is dev->priv, so it is pointing to the allocated area on RAM, I guess.

It looks like serial_in(&com_port->lsr) is trying to read from the hardware register ?

Or reading from malloc area RAM ??

If you go one level deeper you will see that serial_in() is defined at the top in about 5 ways, one of which is used for driver model:

#define serial_in(addr) \ ns16550_readb(com_port, addr - (unsigned char *)com_port)

So it used com_port which is not an parameter. The parameter addr is only used to specify the register. This is actually the same as the non-DM code except in that case the parameter specifies the register and hardware address at the same time.

Without your help, I never could have understood this code. Now it is clearer, thanks! (although this code is really unfortunate...)

It felt like laparoscopic surgery - there is a nicely-healed wound but inside is another story.

...

This is done since the internal NS16550_t type is unfortunately exported all over U-Boot. This is annoying because it is actually an internal register format for the UART. Even worse is the fact that the structure changes depending on CONFIG_SYS_NS16550_REG_SIZE. We can't have this sort of thing in driver model - we need to be able to cope with the device tree specifying all the information that the UART needs. So for driver model:

Agreed. We should pass "reg-shift" from a device tree or a board-file.

If all the board switched to the driver model, the driver code would become much clean.

Yes, I'm looking forward to that day.

...

/*

• For driver model we always use one byte per register, and sort out the
• differences in the driver

*/ #define CONFIG_SYS_NS16550_REG_SIZE (-1)

(see ns16550.h header for where this is used)

I would like to avoid having that type exported and use a different method to pass the UART information around. But it is used in about 30 places . So this approach allows us to move forward bit by bit, without duplicating the UART driver and creating a maintenance headache.

In terns of implementing a new UART driver, are you using device tree?

UniPhier SoCs have not supported the device tree control yet.

I am planning to do the dm conversion with a board file.

...

If so then you should just be able to follow along with Tegra - it's really easy - just copy that serial_tegra.c and adjust the device tree compat string and input clock. Other examples are serial_omap and serial_dw. (See u-boot-dm/working)

These are unfortunate. They are borrowing ns16550 code.

Tegra and many other SOCs have used this code for a while, just with some defines to make it work. I didn't want to copy it.

...

If you are using platform data, then the examples are serial_mxc and serial_pl01x.

I am doing this way.

Anyway, the register map of UniPhier is not 8250-compatible. It cannot borrow ns16550 code.

That's probably for the best.

Regards, Simon