Re: [U-Boot] [PATCH v2 0/3] Add generic early debug UART feature

2015-02-18 Thread Tom Rini 
On Tue, Feb 17, 2015 at 08:22:17PM -0700, Simon Glass wrote:

 +tom, and pruning the cc list a little
 
 Hi,
 
 On 26 January 2015 at 18:27, Simon Glass s...@chromium.org wrote:
  This series adds debug UART infrastructure which can in principle be used on
  any architecture. It works best with those that don't need a stack to call
  functions (e.g. ARM, PowerPC).
 
 I'd really quite like to apply this series. I have used it on PowerPC
 and x86 and found it quite useful. Any objections?

No, lets take it and work from there.

-- 
Tom


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Re: [U-Boot] [PATCH v2 0/3] Add generic early debug UART feature

2015-02-17 Thread Simon Glass 
+tom, and pruning the cc list a little

Hi,

On 26 January 2015 at 18:27, Simon Glass s...@chromium.org wrote:
 This series adds debug UART infrastructure which can in principle be used on
 any architecture. It works best with those that don't need a stack to call
 functions (e.g. ARM, PowerPC).

I'd really quite like to apply this series. I have used it on PowerPC
and x86 and found it quite useful. Any objections?

- Simon
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[U-Boot] [PATCH v2 0/3] Add generic early debug UART feature

2015-01-26 Thread Simon Glass 
This series adds debug UART infrastructure which can in principle be used on
any architecture. It works best with those that don't need a stack to call
functions (e.g. ARM, PowerPC).

This came up in a discussion on the mailing list here:

https://patchwork.ozlabs.org/patch/384613/

My concerns at the time were:
- it doesn't need to be written in assembler
- it doesn't need to be ARM-specific
- it only supports one serial driver

This potentially creates a problem where to support n architectures and m
serial drivers we need n * m lots of assembler-coded functions. For example,
in Linux for ARM we have:

../plat-spear/include/plat/debug-macro.S
../mach-s5pc100/include/mach/debug-macro.S
../mach-shark/include/mach/debug-macro.S
../mach-spear3xx/include/mach/debug-macro.S
../mach-sa1100/include/mach/debug-macro.S
../mach-l7200/include/mach/debug-macro.S
../mach-mv78xx0/include/mach/debug-macro.S
../mach-realview/include/mach/debug-macro.S
../mach-mmp/include/mach/debug-macro.S
../mach-s3c64xx/include/mach/debug-macro.S
../mach-s5pv210/include/mach/debug-macro.S
../mach-clps711x/include/mach/debug-macro.S
../mach-versatile/include/mach/debug-macro.S
../mach-iop32x/include/mach/debug-macro.S
../mach-ebsa110/include/mach/debug-macro.S
../mach-ux500/include/mach/debug-macro.S
../mach-orion5x/include/mach/debug-macro.S
../mach-lpc32xx/include/mach/debug-macro.S
../mach-vt8500/include/mach/debug-macro.S
../mach-rpc/include/mach/debug-macro.S
../mach-kirkwood/include/mach/debug-macro.S
../mach-spear6xx/include/mach/debug-macro.S
../mach-footbridge/include/mach/debug-macro.S
../mach-davinci/include/mach/debug-macro.S
../plat-samsung/include/plat/debug-macro.S
../mach-spear13xx/include/mach/debug-macro.S
../mach-exynos/include/mach/debug-macro.S
../mach-exynos/include/mach/regs-debug.h
../mach-dove/include/mach/debug-macro.S
../mach-omap1/include/mach/debug-macro.S
../mach-u300/include/mach/debug-macro.S
../mach-bcm2835/include/mach/debug-macro.S
../mach-h720x/include/mach/debug-macro.S
../mach-ep93xx/include/mach/debug-macro.S
../mach-gemini/include/mach/debug-macro.S
../mach-s3c24xx/include/mach/debug-macro.S
../mach-at91/include/mach/debug-macro.S
../mach-ixp4xx/include/mach/debug-macro.S
../mach-nomadik/include/mach/debug-macro.S
../mach-cns3xxx/include/mach/debug-macro.S
../mach-mxs/include/mach/debug-macro.S
../mach-iop33x/include/mach/debug-macro.S
../mach-ks8695/include/mach/debug-macro.S
../mach-netx/include/mach/debug-macro.S
../mach-iop13xx/include/mach/debug-macro.S
../mach-integrator/include/mach/debug-macro.S
../mach-msm/include/mach/debug-macro.S
../mach-pxa/include/mach/debug-macro.S
../mach-s5p64x0/include/mach/debug-macro.S
../mach-prima2/include/mach/debug-macro.S
../mach-omap2/include/mach/debug-macro.S

This series provides a possible alternative. It works by allowing any serial
driver to export one init function and provide a putc() function. These
can be used to output debug data before the real serial driver is available.
Only one debug UART can be used at a time, and its address and serial clock
must be provided statically in Kconfig.

This implementation does not depend on driver model being set up, and it is
possible for it to operate without a stack on some architectures (e.g.
PowerPC, ARM). It provides the same features as the ARM-specific debug.S but
with more UART and architecture support.

As an example, here is the code generated for printch() by gcc 4.8 on ARM
using the ns16550 driver (Tegra Seaboard):

0013b3b0 printch:
  13b3b0:   e59f201cldr r2, [pc, #28]   ; 13b3d4 printch+0x24
  13b3b4:   e5d23305ldrbr3, [r2, #773]  ; 0x305
  13b3b8:   e6ef3073uxtbr3, r3
  13b3bc:   e3130020tst r3, #32
  13b3c0:   0afbbeq 13b3b4 printch+0x4
  13b3c4:   e6ef0070uxtbr0, r0
  13b3c8:   e59f3004ldr r3, [pc, #4]; 13b3d4 printch+0x24
  13b3cc:   e5c30300strbr0, [r3, #768]  ; 0x300
  13b3d0:   e12fff1ebx  lr
  13b3d4:   70006000.word   0x70006000

The PowerPC 4xx code (ELDK-5.3) for printhex8() is this:

0102db44 printhex8:
 102db44:   3c c0 ef 60 lis r6,-4256
 102db48:   3c e0 ef 60 lis r7,-4256
 102db4c:   39 20 00 1c li  r9,28
 102db50:   60 c6 03 05 ori r6,r6,773
 102db54:   60 e7 03 00 ori r7,r7,768
 102db58:   7c 6a 4c 30 srw r10,r3,r9
 102db5c:   55 4a 07 3e clrlwi  r10,r10,28
 102db60:   2b 8a 00 09 cmplwi  cr7,r10,9
 102db64:   39 0a 00 30 addir8,r10,48
 102db68:   40 9d 00 08 ble-cr7,102db70 printhex8+0x2c
 102db6c:   39 0a 00 57 addir8,r10,87
 102db70:   7c 00 04 ac sync
 102db74:   89 46 00 00 lbz r10,0(r6)
 102db78:   0c 0a 00 00 twi 0,r10,0
 102db7c:   4c 00 01 2c isync
 102db80:   55 4a 06 b4 rlwinm  r10,r10,0,26,26
 102db84:   71 45 00 ff andi.