[U-Boot] __attribute__((__packed__)) switching to byte-access on ARM

[Guennadi Liakhovetski]

Hi

As I remarked in the opening email to the SMDK6400 patch-series, I've got 
a strange problem, I cannot understand.

Here're the c-code:

typedef struct {
	volatile u32	TCNTB;
	volatile u32	TCMPB;
	volatile u32	TCNTO;
} s3c64xx_timer;

typedef struct {
	volatile u32	TCFG0;
	volatile u32	TCFG1;
	volatile u32	TCON;
	s3c64xx_timer	ch[4];
	volatile u32	TCNTB4;
	volatile u32	TCNTO4;
} s3c64xx_timers;


static s3c64xx_timers *s3c64xx_get_base_timers(void)
{
	return (s3c64xx_timers *)ELFIN_TIMER_BASE;
}

/* macro to read the 16 bit timer */
static inline ulong read_timer(void)
{
	s3c64xx_timers *const timers = s3c64xx_get_base_timers();

	return timers->TCNTO4;
}

The respective assembly code is quite simple:

00000000 <read_timer>:
   0:	e59f3004 	ldr	r3, [pc, #4]	; c <timer_load_val>
   4:	e5930040 	ldr	r0, [r3, #64]
   8:	e12fff1e 	bx	lr
   c:	7f006000 	swivc	0x00006000

Perfect. Now, if I make the two structs above packed, I get this assembly:

00000000 <read_timer>:
   0:	e59f301c 	ldr	r3, [pc, #28]	; 24 <.text+0x24>
   4:	e5d30040 	ldrb	r0, [r3, #64]
   8:	e5d32041 	ldrb	r2, [r3, #65]
   c:	e5d31042 	ldrb	r1, [r3, #66]
  10:	e1800402 	orr	r0, r0, r2, lsl #8
  14:	e5d33043 	ldrb	r3, [r3, #67]
  18:	e1800801 	orr	r0, r0, r1, lsl #16
  1c:	e1800c03 	orr	r0, r0, r3, lsl #24
  20:	e12fff1e 	bx	lr
  24:	7f006000 	swivc	0x00006000

which converts all accesses to the structure to 8-bit... Ideas? Toolchain 
eldk-4.1. U-Boot from nand/testing git with the patches I just sent to the 
list, configured for smdk6400_config.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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