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