[PATCH v2 06/12] at91: smc: Adds helper functions to validate and clip the smc timings.

[Jean-Jacques Hiblot]

2014/1/15 Nicolas Ferre <nicolas.ferre at atmel.com>:
> On 09/01/2014 13:31, Jean-Jacques Hiblot :
>> This patchs implememnts 2 functions to help with the configuration of a
>> chip-select's timing:
>> * sam9_smc_check_cs_configuration : checks that the values would fit in the
>>   registers.
>> * sam9_smc_clip_cs_configuration : clip the values to their maximum.
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot at traphandler.com>
>> ---
>>  arch/arm/mach-at91/include/mach/at91sam9_smc.h |  2 +
>>  arch/arm/mach-at91/sam9_smc.c                  | 77 ++++++++++++++++++++++++++
>>  2 files changed, 79 insertions(+)
>>
>> diff --git a/arch/arm/mach-at91/include/mach/at91sam9_smc.h b/arch/arm/mach-at91/include/mach/at91sam9_smc.h
>> index c3e29311..615ac56 100644
>> --- a/arch/arm/mach-at91/include/mach/at91sam9_smc.h
>> +++ b/arch/arm/mach-at91/include/mach/at91sam9_smc.h
>> @@ -47,6 +47,8 @@ extern void sam9_smc_read_mode(int id, int cs, struct sam9_smc_config *config);
>>  extern void sam9_smc_write_mode(int id, int cs, struct sam9_smc_config *config);
>>  extern void sam9_smc_cs_read(void __iomem *, struct sam9_smc_config *config);
>>  extern void sam9_smc_cs_configure(void __iomem *, struct sam9_smc_config *cfg);
>> +extern int sam9_smc_check_cs_configuration(struct sam9_smc_config *config);
>> +extern void sam9_smc_clip_cs_configuration(struct sam9_smc_config *config);
>>  #endif
>>
>>  #define AT91_SMC_SETUP               0x00                            /* Setup Register for CS n */
>> diff --git a/arch/arm/mach-at91/sam9_smc.c b/arch/arm/mach-at91/sam9_smc.c
>> index d7a6156..fe3c492 100644
>> --- a/arch/arm/mach-at91/sam9_smc.c
>> +++ b/arch/arm/mach-at91/sam9_smc.c
>> @@ -23,6 +23,83 @@
>>
>>  static void __iomem *smc_base_addr[2];
>>
>> +static int count_trailing_zeroes(u32 x)
>
> Don't we have something generic for this?
>
> Check include/asm-generic/bitops/count_zeros.h

I wonder how I could have missed this one :o)

>
>> +{
>> +     int ret = 0;
>> +     if (!(x & 0xFFFF)) {
>> +             ret += 16;
>> +             x = x >> 16;
>> +     }
>> +     if (!(x & 0xFF)) {
>> +             ret += 8;
>> +             x = x >> 8;
>> +     }
>> +     if (!(x & 0xF)) {
>> +             ret += 4;
>> +             x = x >> 4;
>> +     }
>> +     if (!(x & 0x3)) {
>> +             ret += 2;
>> +             x = x >> 2;
>> +     }
>> +     if (!(x & 0x1)) {
>> +             ret += 1;
>> +             x = x >> 1;
>> +     }
>> +     if (!(x & 0x1))
>> +             ret += 1;
>> +
>> +     return ret;
>> +}
>> +
>> +
>> +#define __CHECK_CFG(config, x, y)  do {\
>> +     if (x##_(config->y) > x) {\
>> +             pr_debug("error: %s (0x%x) is out of range\n", #y,\
>> +                     config->y >> count_trailing_zeroes(x));\
>> +             return -EINVAL;\
>> +             } \
>> +     } while (0)
>
> I do not like the use of macro for this. You can convert them to
> functions and it would increase readability. I am pretty confident that
> gcc will optimize it so that is won't impact performance.

It's not a matter of performance. I wanted to use the stringification
for the debug message.

>
>> +int sam9_smc_check_cs_configuration(struct sam9_smc_config *config)
>> +{
>> +     __CHECK_CFG(config, AT91_SMC_NWESETUP, nwe_setup);
>> +     __CHECK_CFG(config, AT91_SMC_NCS_WRSETUP, ncs_write_setup);
>> +     __CHECK_CFG(config, AT91_SMC_NRDSETUP, nrd_setup);
>> +     __CHECK_CFG(config, AT91_SMC_NCS_RDSETUP, ncs_read_setup);
>> +     __CHECK_CFG(config, AT91_SMC_NWEPULSE, nwe_pulse);
>> +     __CHECK_CFG(config, AT91_SMC_NCS_WRPULSE, ncs_write_pulse);
>> +     __CHECK_CFG(config, AT91_SMC_NRDPULSE, nrd_pulse);
>> +     __CHECK_CFG(config, AT91_SMC_NCS_RDPULSE, ncs_read_pulse);
>> +     __CHECK_CFG(config, AT91_SMC_NWECYCLE, write_cycle);
>> +     __CHECK_CFG(config, AT91_SMC_NRDCYCLE, read_cycle);
>> +     __CHECK_CFG(config, AT91_SMC_TDF, tdf_cycles);
>> +     return 0;
>> +}
>> +
>> +#define __CLIP_CFG(config, x, y)  do {\
>> +     if (x##_(config->y) > x) {\
>> +             config->y = x >> count_trailing_zeroes(x);\
>> +             pr_debug("clipping %s to %d\n", #y, config->y);\
>> +             } \
>> +     } while (0)
>
> Ditto.
>
>> +
>> +void sam9_smc_clip_cs_configuration(struct sam9_smc_config *config)
>> +{
>> +     __CLIP_CFG(config, AT91_SMC_NWESETUP, nwe_setup);
>> +     __CLIP_CFG(config, AT91_SMC_NCS_WRSETUP, ncs_write_setup);
>> +     __CLIP_CFG(config, AT91_SMC_NRDSETUP, nrd_setup);
>> +     __CLIP_CFG(config, AT91_SMC_NCS_RDSETUP, ncs_read_setup);
>> +     __CLIP_CFG(config, AT91_SMC_NWEPULSE, nwe_pulse);
>> +     __CLIP_CFG(config, AT91_SMC_NCS_WRPULSE, ncs_write_pulse);
>> +     __CLIP_CFG(config, AT91_SMC_NRDPULSE, nrd_pulse);
>> +     __CLIP_CFG(config, AT91_SMC_NCS_RDPULSE, ncs_read_pulse);
>> +     __CLIP_CFG(config, AT91_SMC_NWECYCLE, write_cycle);
>> +     __CLIP_CFG(config, AT91_SMC_NRDCYCLE, read_cycle);
>> +     __CLIP_CFG(config, AT91_SMC_TDF, tdf_cycles);
>> +
>> +}
>> +
>>  static void sam9_smc_cs_write_mode(void __iomem *base,
>>                                       struct sam9_smc_config *config)
>>  {
>>
>
>
> --
> Nicolas Ferre