Re: [PATCH 4/7] Add USB booting capabilities to OMAP

[vj <vicencb@gmail.com>]

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Hi Sascha,
 I've been playing with passing some data from first to second stage using
Jan's patches.
It worked fine, but in my case I want to store this data on a global
variable, which is cleared as it's in the BSS.
There is a clean workarround to this issue?

Thanks,
  Vicente.

On Wed, Sep 26, 2012 at 9:45 AM, Sascha Hauer <s.hauer@pengutronix.de>wrote:

> On Wed, Sep 26, 2012 at 12:59:51AM +0200, vj wrote:
> > ---
> >  arch/arm/cpu/cpu.c                              |   1 +
> >  arch/arm/lib/barebox.lds.S                      |  10 +
> >  arch/arm/mach-omap/Kconfig                      |  21 +
> >  arch/arm/mach-omap/Makefile                     |   1 +
> >  arch/arm/mach-omap/include/mach/omap4_rom_usb.h | 146 +++++
> >  arch/arm/mach-omap/omap4_generic.c              |   2 +
> >  arch/arm/mach-omap/omap4_rom_usb.c              | 189 ++++++
> >  arch/arm/mach-omap/xload.c                      |  26 +
> >  scripts/.gitignore                              |   1 +
> >  scripts/Makefile                                |   3 +
> >  scripts/usbboot.c                               | 797
> ++++++++++++++++++++++++
> >  11 files changed, 1197 insertions(+)
> >  create mode 100644 arch/arm/mach-omap/include/mach/omap4_rom_usb.h
> >  create mode 100644 arch/arm/mach-omap/omap4_rom_usb.c
> >  create mode 100644 scripts/usbboot.c
> >
> > diff --git a/arch/arm/cpu/cpu.c b/arch/arm/cpu/cpu.c
> > index 71ef8c0..05343de 100644
> > --- a/arch/arm/cpu/cpu.c
> > +++ b/arch/arm/cpu/cpu.c
> > @@ -89,6 +89,7 @@ void arch_shutdown(void)
> >               : "r0", "r1", "r2", "r3", "r6", "r10", "r12", "lr", "cc",
> "memory"
> >       );
> >  #endif
> > +     __asm__ __volatile__ ("cpsid i\n");
> >  }
> >
> >  #ifdef CONFIG_THUMB2_BAREBOX
> > diff --git a/arch/arm/lib/barebox.lds.S b/arch/arm/lib/barebox.lds.S
> > index a69013f..ff7b63d 100644
> > --- a/arch/arm/lib/barebox.lds.S
> > +++ b/arch/arm/lib/barebox.lds.S
> > @@ -97,6 +97,16 @@ SECTIONS
> >       __bss_start = .;
> >       .bss : { *(.bss*) }
> >       __bss_stop = .;
> > +#ifdef CONFIG_SHARE_USB_HANDLE
> > +    /*
> > +     * Reserve space for the USB handle
> > +     */
> > +     . = CONFIG_USB_HANDLE_HANDOVER;
> > +     . = ALIGN(4);
> > +     __usb_handle = .;
> > +     /* . += sizeof(struct usb); */
> > +     . += 84;
> > +#endif
>
> If I understand correctly the first stage loader puts some data here
> where a second stage barebox (configured with the same value for
> CONFIG_USB_HANDLE_HANDOVER) will pick it up.
>
> This seems to be a bit fragile. Fortunately Jan has posted a series
> that gives the control of the reset vector to the boards, which means
> that both stages do not have to agree on an addres, but instead a
> pointer can be passed from the first to the second stage.
>
> > +int usb_open(void)
>
> So this uses the OMAP4 ROM to do USB communication, right? The functions
> should have a omap_rom_* prefix then, otherwise it's not clear for a
> reader which context these functions have.
>
> The calling of the ROM code btw explains why the setting of VBAR breaks
> USB boot. The ROM probably uses the vectors.
>
> > +
> > +     n = rom_get_per_driver(&pusb->io, boot->device_type);
> > +     if (n)
> > +             return n;
> > +
> > +     pusb->dread.xfer_mode = boot->xfer_mode;
> > +     pusb->dread.options = boot->options;
> > +     pusb->dread.device_type = boot->device_type;
> > +
> > +     pusb->dwrite.xfer_mode = boot->xfer_mode;
> > +     pusb->dwrite.options = boot->options;
> > +     pusb->dwrite.device_type = boot->device_type;
> > +#else
> > +#ifdef CONFIG_MMU
> > +#error USB communications not working under MMU
>
> You can add the following to CONFIG_OMAP4_USB_BOOT instead:
>
>         depends on !MMU
>
> So that an invalid config is not allowed in the first place.
>
>
> > diff --git a/scripts/usbboot.c b/scripts/usbboot.c
>
> This should also be named omap4-usbboot.c, or maybe, if the works on
> other OMAPs, just omap-usboot.c
>
> Sascha
>
> --
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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>

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