[U-Boot] [PATCH v2 09/11] S3C24XX: Add NAND Flash driver

Tom Rini
2012-09-17T16:57:57Z

On Sun, Sep 16, 2012 at 10:16:47AM +0100, Jos? Miguel Gon?alves wrote:
> On 09/14/2012 08:01 PM, Tom Rini wrote:
> >On Fri, Sep 14, 2012 at 07:45:40PM +0100, Jos? Miguel Gon?alves wrote:
> >>On 14-09-2012 19:21, Marek Vasut wrote:
> >>>Dear Jos? Miguel Gon?alves,
> >>>
> >>>>NAND Flash driver with HW ECC for the S3C24XX SoCs.
> >>>>Currently it only supports SLC NAND chips.
> >>>>
> >>>>Signed-off-by: Jos? Miguel Gon?alves <jose.goncalves@inov.pt>
> >>>[...]
> >>>
> >>>>+#include <common.h>
> >>>>+#include <nand.h>
> >>>>+#include <asm/io.h>
> >>>>+#include <asm/arch/s3c24xx_cpu.h>
> >>>>+#include <asm/errno.h>
> >>>>+
> >>>>+#define MAX_CHIPS 2
> >>>>+static int nand_cs[MAX_CHIPS] = { 0, 1 };
> >>>>+
> >>>>+#ifdef CONFIG_SPL_BUILD
> >>>>+#define printf(arg...) do {} while (0)
> >>>This doesn't seem quite right ...
> >>>
> >>>1) this should be in CPU directory
> >>>2) should be enabled only if CONFIG_SPL_SERIAL_SUPPORT is not set
> >>>3) should be inline function, not a macro
> >>1) and 3) OK.
> >>Don't quite understand 2). I want to remove the printfs in the SPL
> >>build, as it would blown up the internal SoC RAM space available.
> >>So why add a condition with CONFIG_SPL_SERIAL_SUPPORT?
> >You've got 8KB, based on the final patch in the series. At least in my
> >SPL series that's still enough to get you printf/puts (I believe 4kb was
> >the cutoff where that had to be dropped).
> >
>
> Barely:
>
> $ size u-boot-spl
> text data bss dec hex filename
> 3337 8 588 3933 f5d u-boot-spl
>
> $ size u-boot-spl-printf
> text data bss dec hex filename
> 7968 8 604 8580 2184 u-boot-spl-printf
>
> The printf is not so important that justifies exhausting the IRAM
> space available and preventing any future SPL expansion...

There's two parts to this:
- What else can you do in a single binary, in theory? Is there boot
medium detection and you would want to have, for example, NAND and SD
support in the same binary? I would say memory is meant for using,
but this is a board maintainer decision and that's you :)
- We have a define today (CONFIG_SPL_LIBCOMMON_SUPPORT) that toggles
printf or no printf. If we really need to say yes to
LIBCOMMON_SUPPORT and no to printf, we need finer grained config
options and then a do-nothing printf is used for SPL. Doing the
opt-out driver by driver just punts this problem down the road to the
next developer and that's not very nice (and adding
CONFIG_SPL_PRINTF_SUPPORT shouldn't be a big patch, modify a few
Makefiles, update a bunch of config files, add
common/spl/dummy_funcs.c and a __weak printf).

--
Tom
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