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

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Message-ID: <52D65880.10301@atmel.com>
Date:	Wed, 15 Jan 2014 10:44:32 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Jean-Jacques Hiblot <jjhiblot@...phandler.com>
CC:	<b.brezillon@...rkiz.com>, <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 06/12] at91: smc: Adds helper functions to validate
 and clip the smc timings.

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@...phandler.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

> +{
> +	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.

> +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
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