[U-Boot] [PATCH v2 09/16] mtd/nand/tegra: alignment workaround

[Scott Wood <scottwood@freescale.com>]

On Tue, 2015-07-28 at 03:55 +0200, Marcel Ziswiler wrote:
> On 27 July 2015 21:57:14 CEST, Scott Wood <scottwood@freescale.com> wrote:
> > On Tue, 2015-07-21 at 00:35 +0200, Marcel Ziswiler wrote:
> > > From: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> > > 
> > > Integrate cache alignment bounce buffer to workaround issues as
> > follows:
> > > 
> > > Loading file '/boot/zImage' to addr 0x01000000 with size 4499152 
> > > (0x0044a6d0)...
> > > ERROR: v7_dcache_inval_range - start address is not aligned -
> > 0x1f7f0108
> > > ERROR: v7_dcache_inval_range - stop address is not aligned -
> > 0x1f7f1108
> > > Done
> > > Kernel image @ 0x1000000 [ 0x000000 - 0x44a6d0 ]
> > > 
> > > Starting kernel ...
> > > 
> > > undefined instruction
> > > pc : [<005ff03c>]          lr : [<0000800c>]
> > > sp : 0144b6e8  ip : 01000188     fp : 0144a6c8
> > > r10: 00000000  r9 : 411fc090     r8 : 00000100
> > > r7 : 00000cfb  r6 : 0144a6d0     r5 : 00000000  r4 : 00008000
> > > r3 : 0000000c  r2 : 00000100     r1 : 00000cfb  r0 : 00000000
> > > Flags: nZCv  IRQs off  FIQs off  Mode SVC_32
> > > Resetting CPU ...
> > > 
> > > Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> > > ---
> > > Changes in v2:
> > > Migrated to using generic bounce buffer implementation as suggested
> > by 
> > > Simon.
> > 
> > I didn't see Simon's suggestion, but what is the general policy in
> > U-Boot 
> > supposed to be for I/O alignment?  Responsibility of the API user, or
> > of the 
> > driver?  Are there other drivers with the same problem?
> 
> Well, well. You got us into some ruff terrain right there. Remember I have 
> some other alignment patches awaiting acceptance (e.g U-Boot's MTD and most 
> possibly other subsystems are deeply broken in that respect) but even with 
> those I failed booting a kernel loaded from UBIFS so I started having my 
> doubts whether or not this is truly possible without bouncing. At least 
> Tegra's MMC driver just bounces as well.

OK.  With users such as UBI that are shared with kernel code, it might be 
difficult to enforce a caller-aligns model.

-Scott