Hi Masahiro, On 1 October 2014 05:23, Masahiro Yamada <[email protected]> wrote: > Hi Simon, > > > > I am looking at the driver-model serial code. > > > I notice driver-model serial code uses ".data" section > for storing the current device even before relocation. > > > This code in drivers/serial/serial-uclass.c: > > /* The currently-selected console serial device */ > struct udevice *cur_dev __attribute__ ((section(".data"))); > > > > In my understanding, we should not write any data to > .data section before relocation. > > > Let's say we are booting U-Boot from NOR flash. > > Before relocation, everything (including .data section) > is placed on NOR flash which is read-only. > (Please point out if I am wrong.) > > We are only allowed to write data to the stack, gd_t, bd_t > and malloc area (if CONFIG_SYS_MALLOC_F_LEN is defined) > before relocation, I think. > > > > I think that is why pre-driver-model serial uses a hard-coded > default serial port before relocation. > > > This code in driver/serial/serial.c: > > if (!(gd->flags & GD_FLG_RELOC)) > dev = default_serial_console(); > else if (!serial_current) > dev = default_serial_console(); > else > dev = serial_current; > > > > > My question is, does printf() work > with driver-model UART and XIP device such NOR flash?
The global_data structure needs to go somewhere, even before relocation. On ARM this is general SRAM I suppose. In your case I think you have some cache RAM to use. Do you use SPL? The pre-reloc malloc() area goes below global_data so uses the same mechanism. Yes it is true that strictly speaking we should not use data before relocation. I suppose we could move cur_dev to global_data instead for this particular case. It doesn't really scale to other drivers, but then I expect that only serial needs to keep a 'current' pointer before relocation, and even that will eventually go away once the serial stuff is cleaned up. So let me know if that solution works. Regards, Simon _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
