Re: [SeaBIOS] [PATCH] megasas: Add boot support for LSI MegaRAID SAS

[Hannes Reinecke]

On 11/13/2012 01:39 AM, Kevin O'Connor wrote:
> On Mon, Nov 12, 2012 at 03:45:19PM +0100, Hannes Reinecke wrote:
> > This patch adds support for LSI MegaRAID SAS controllers.
> > Currently only 8708EM2 is supported.
>
> Thanks.  Some comments below.
>
> [...]
> > SET_LOWFLAT(frame->cmd, MFI_CMD_LD_SCSI_IO);
>
> [...]
> > mlun->frame = memalign_high(256, sizeof(struct megasas_cmd_frame));
>
> Something's not right here.  If the memory is allocated in high ram,
> then it isn't accessible via GET/SET_LOW.  Only memalign_low memory is
> available with the GET/SET_LOW macros.

I'm not at all surprised. I've still only the haziest of ideas of 
how to use memalign_XX and GET/SET macros.

I actually took the ahci code as a reference on how to use those 
macros, and they are using GET/SET_LOW and memalign_tmp().

So yeah, I'll be converting it to memalign_tmp().
> [...]
> > struct megasas_cmd_frame *frame = memalign_high(256, sizeof(*frame));
> > int i;
> > memset(&ld_list, 0, sizeof(ld_list));
> > memset(frame, 0, sizeof(*frame));
> > frame->cmd = MFI_CMD_DCMD;
> > frame->cmd_status = 0xFF;
> > frame->sge_count = 1;
> > frame->flags = 0x0011;
> > frame->data_xfer_len = sizeof(ld_list);
> > frame->dcmd.opcode = 0x03010000;
> > frame->dcmd.sgl_addr = (u32)MAKE_FLATPTR(GET_SEG(SS), &ld_list);
> > frame->dcmd.sgl_len = sizeof(ld_list);
> > frame->context = (u32)frame;
> > if (megasas_fire_cmd(iobase, frame) != 0)
> >    return;
>
> Missing free(frame).

Yep.
> > dprintf(1, "%d LD found\n", ld_list.count);
> > for (i = 0; i < ld_list.count; i++) {
> >    dprintf(1, "LD %d:%d state 0x%x\n",
> >            ld_list.lds[i].target, ld_list.lds[i].lun,
> >            ld_list.lds[i].state);
> >    if (ld_list.lds[i].state != 0) {
> >        megasas_add_lun(pci, iobase,
> >                        ld_list.lds[i].target, ld_list.lds[i].lun);
> >    }
> > }
> > free(frame);
> >
> > +}
>
> Although valid, it's not a good idea to use memalign_high for
> temporary space.  One should use memalign_tmp for that purpose.

The thing here is that megasas_fire_cmd() is a generic function, so 
it needs to work in both 16 and 32-bit environs. So the frame 
pointer passed to this function needs to reference the same segment.

And this is where things get confused.
I've converted the driver to use memalign_tmp() for allocating space 
for the frame. Which works.

But then you claim that GET/SET_LOW won't work for space located
high memory. However, when using memalign_tmp() it's impossible to 
tell where the space is located at:

static inline void *memalign_tmp(u32 align, u32 size) {
     void *ret = memalign_tmphigh(align, size);
     if (ret)
         return ret;
     return memalign_tmplow(align, size);
}

So which macro do have to use to access this memory?
And why does GET/SET_LOW work?

Cheers,

Hannes