[PATCH] cfi_flash: Fix devicetree address determination

[Simon Glass]

Hi André,

On Wed, 23 Sep 2020 at 09:39, André Przywara <andre.przywara at arm.com> wrote:
>
> On 23/09/2020 06:26, Stefan Roese wrote:
> > Hi Simon,
> >
> > On 22.09.20 15:51, Simon Glass wrote:
> >> Hi Stefan,
> >>
> >> On Mon, 21 Sep 2020 at 07:28, Stefan Roese <sr at denx.de> wrote:
> >>>
> >>> Hi Andre,
> >>>
> >>> (added Simon)
> >>>
> >>> On 18.09.20 19:45, Andre Przywara wrote:
> >>>> The cfi-flash driver uses an open-coded version of the generic
> >>>> algorithm to decode and translate multiple frames of a "reg" property.
> >>>>
> >>>> This starts off the wrong foot by using the address-cells and
> >>>> size-cells
> >>>> properties of *this* very node, and not of the parent. This somewhat
> >>>> happened to work back when we were using a wrong default size of 2,
> >>>> but broke about a year ago with commit 0ba41ce1b781 ("libfdt: return
> >>>> correct value if #size-cells property is not present").
> >>>>
> >>>> Instead of fixing the reinvented wheel, just use the generic function
> >>>> that does all of this properly.
> >>>>
> >>>> This fixes U-Boot on QEMU (outside of EL1), which was crashing due to
> >>>> decoding a wrong start address:
> >>>> DRAM:  1 GiB
> >>>> Flash: "Synchronous Abort" handler, esr 0x96000044
> >>>> elr: 00000000000211dc lr : 00000000000211b0 (reloc)
> >>>> elr: 000000007ff5e1dc lr : 000000007ff5e1b0
> >>>> x0 : 00000000000000f0 x1 : 000000007ff5e1d8
> >>>> x2 : 000000007edfbc48 x3 : 0000000000000000
> >>>> x4 : 0000000000000000 x5 : 00000000000000f0
> >>>> x6 : 000000007edfbc2c x7 : 0000000000000000
> >>>> x8 : 000000007ffd8d70 x9 : 000000000000000c
> >>>> x10: 0400000000000003 x11: 0000000000000055
> >>>>        ^^^^^^^^^^^^^^^^
> >>>>
> >>>> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> >>>> ---
> >>>>    drivers/mtd/cfi_flash.c | 25 +++++++------------------
> >>>>    1 file changed, 7 insertions(+), 18 deletions(-)
> >>>>
> >>>> diff --git a/drivers/mtd/cfi_flash.c b/drivers/mtd/cfi_flash.c
> >>>> index b7289ba5394..656ff326e17 100644
> >>>> --- a/drivers/mtd/cfi_flash.c
> >>>> +++ b/drivers/mtd/cfi_flash.c
> >>>> @@ -2468,29 +2468,18 @@ unsigned long flash_init(void)
> >>>>    #ifdef CONFIG_CFI_FLASH /* for driver model */
> >>>>    static int cfi_flash_probe(struct udevice *dev)
> >>>>    {
> >>>> -     const fdt32_t *cell;
> >>>> -     int addrc, sizec;
> >>>> -     int len, idx;
> >>>> +     fdt_addr_t addr;
> >>>> +     fdt_size_t size;
> >>>> +     int idx;
> >>>>
> >>>> -     addrc = dev_read_addr_cells(dev);
> >>>> -     sizec = dev_read_size_cells(dev);
> >>>> -
> >>>> -     /* decode regs; there may be multiple reg tuples. */
> >>>> -     cell = dev_read_prop(dev, "reg", &len);
> >>>> -     if (!cell)
> >>>> -             return -ENOENT;
> >>>> -     idx = 0;
> >>>> -     len /= sizeof(fdt32_t);
> >>>> -     while (idx < len) {
> >>>> -             phys_addr_t addr;
> >>>> -
> >>>> -             addr = dev_translate_address(dev, cell + idx);
> >>>> +     for (idx = 0; idx < CFI_MAX_FLASH_BANKS; idx++) {
> >>>> +             addr = devfdt_get_addr_size_index(dev, idx, &size);
> >>>> +             if (addr == FDT_ADDR_T_NONE)
> >>>> +                     break;
> >>>>
> >>>>                flash_info[cfi_flash_num_flash_banks].dev = dev;
> >>>>                flash_info[cfi_flash_num_flash_banks].base = addr;
> >>>>                cfi_flash_num_flash_banks++;
> >>>> -
> >>>> -             idx += addrc + sizec;
> >>>>        }
> >>>>        gd->bd->bi_flashstart = flash_info[0].base;
> >>>>
> >>>>
> >>>
> >>> This fails on my Octeon MIPS64 platform "octeon_ebb7304". I did some
> >>> debugging and found that here "of_offset" is a 64 bit value (type long)
> >>> which gets truncated in dev_of_offset() to 32 bit (type int).
> >>>
> >>> This problem only arises when of_live_active() is set. Here, "of_offset"
> >>> holds a pointer AFACT and truncating it to 32 bits breaks things.
> >>>
> >>> I'm wondering why this did not hit me earlier on this 64bit platform.
> >>> Simon, do you have a quick idea how to solve this?
> >>
> >> Well I don't think ofnode should use long for of_offset, since int
> >> should be enough.
> >>
> >> ofnode_to_offset() converts an ofnode to a DT offset but only if it is
> >> not using livetree. With livetree there are no offsets so this is not
> >> going to work. If you define OF_CHECKS you will see that.
> >
> > This does not work right now. I'll send a patch fixing compiling with
> > OF_CHECK enabled shortly.
> >
> >> Note that an ofnode can either hold a pointer or an offset. There are
> >> detailed comments on ofnode_union to explain how it is supposed to
> >> work.
> >
> > Right. Thanks for all the detailed infos in the header. The main issue
> > seems to be, that this CFI patch uses a function from fdtaddr.c
> > (devfdt_get_addr_size_index), which unconditionally uses dev_of_offset()
> > without checking if livetree is enabled or not. This breaks on my
> > 64 bit platform (see below).
> >
> >> This patch looks correct to me, but perhaps there is something else
> >> going on?
> >
> > Making this change below, works for me:
> >
> > -        addr = devfdt_get_addr_size_index(dev, idx, &size);
> > +        addr = dev_read_addr_index(dev, idx);
>
> Ouch, sorry for that!
>
> One thing I noticed: Technically this fix is no longer needed, since
> Heinrich's patch ae6b33dcc342 ("dm: fix ofnode_read_addr/size_cells()")
> recently fixed that particular issue (I missed that one when doing the
> bisect earlier).
>
> However I still consider this patch here useful, since it removes code
> duplication (and the original bug gives a good rationale for that!).
> So I will repost this one here, but leave it up to you whether to merge
> it or not.
>
> Also: this function was the only user of dev_read_{addr,size}_cells().
> Shall we consequently remove them? They have this somewhat surprising
> feature of querying the parent now, which prevents them from being used
> when someone want to determine the current #a-c and #s-c applicable for
> subnodes, for instance.

Yes I agree that is surprising. If we don't think they will be useful
in future I think removing them is OK.

>
> > Maybe we should make sure, that all functions from fdtaddr.c are not
> > used with livetree active? To prevent similar issues using devfdt_foo()
> > functions with livetree active.
> That sounds useful, but can this be done easily?

We could add a check at the start of each function, perhaps.

Regards,
Simon