Re: [PATCH 7/8 v2] ARM OMAP2+ GPMC: calculate GPMCFCLKDIVIDER based on WAITMONITORINGTIME

[Roger Quadros <rogerq@ti.com>]

On 24/02/15 22:05, Robert ABEL wrote:
> The WAITMONITORINGTIME is expressed as a number of GPMC_CLK clock cycles,
> even though the access is defined as asynchronous, and no GPMC_CLK clock
> is provided to the external device. Still, GPMCFCLKDIVIDER is used as a divider
> for the GPMC clock, so it must be programmed to define the
> correct WAITMONITORINGTIME delay.
> 
> Calculate GPMCFCLKDIVIDER independent of gpmc,sync-clk-ps in DT for
> truly asynchronous accesses, i.e. both read and write asynchronous.
> 
> Signed-off-by: Robert ABEL <rabel@cit-ec.uni-bielefeld.de>
> ---
>  arch/arm/mach-omap2/gpmc-nand.c    | 17 ++++-----
>  arch/arm/mach-omap2/gpmc-onenand.c |  4 +--
>  drivers/memory/omap-gpmc.c         | 74 ++++++++++++++++++++++++++++++++++----
>  include/linux/omap-gpmc.h          |  2 +-
>  4 files changed, 80 insertions(+), 17 deletions(-)
> 

./scripts/checkpatch.pl detects some styling errors.

> diff --git a/arch/arm/mach-omap2/gpmc-nand.c b/arch/arm/mach-omap2/gpmc-nand.c
> index d5951b1..e863a59 100644
> --- a/arch/arm/mach-omap2/gpmc-nand.c
> +++ b/arch/arm/mach-omap2/gpmc-nand.c
> @@ -96,14 +96,6 @@ int gpmc_nand_init(struct omap_nand_platform_data *gpmc_nand_data,
>  	gpmc_nand_res[1].start = gpmc_get_client_irq(GPMC_IRQ_FIFOEVENTENABLE);
>  	gpmc_nand_res[2].start = gpmc_get_client_irq(GPMC_IRQ_COUNT_EVENT);
>  
> -	if (gpmc_t) {
> -		err = gpmc_cs_set_timings(gpmc_nand_data->cs, gpmc_t);
> -		if (err < 0) {
> -			pr_err("omap2-gpmc: Unable to set gpmc timings: %d\n", err);
> -			return err;
> -		}
> -	}
> -
>  	memset(&s, 0, sizeof(struct gpmc_settings));
>  	if (gpmc_nand_data->of_node)
>  		gpmc_read_settings_dt(gpmc_nand_data->of_node, &s);
> @@ -111,6 +103,15 @@ int gpmc_nand_init(struct omap_nand_platform_data *gpmc_nand_data,
>  		gpmc_set_legacy(gpmc_nand_data, &s);
>  
>  	s.device_nand = true;
> +
> +	if (gpmc_t) {
> +		err = gpmc_cs_set_timings(gpmc_nand_data->cs, gpmc_t, &s);
> +		if (err < 0) {
> +			pr_err("omap2-gpmc: Unable to set gpmc timings: %d\n", err);
> +			return err;
> +		}
> +	}
> +
>  	err = gpmc_cs_program_settings(gpmc_nand_data->cs, &s);
>  	if (err < 0)
>  		goto out_free_cs;
> diff --git a/arch/arm/mach-omap2/gpmc-onenand.c b/arch/arm/mach-omap2/gpmc-onenand.c
> index 53d197e..f899e77 100644
> --- a/arch/arm/mach-omap2/gpmc-onenand.c
> +++ b/arch/arm/mach-omap2/gpmc-onenand.c
> @@ -293,7 +293,7 @@ static int omap2_onenand_setup_async(void __iomem *onenand_base)
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = gpmc_cs_set_timings(gpmc_onenand_data->cs, &t);
> +	ret = gpmc_cs_set_timings(gpmc_onenand_data->cs, &t, &onenand_async);
>  	if (ret < 0)
>  		return ret;
>  
> @@ -331,7 +331,7 @@ static int omap2_onenand_setup_sync(void __iomem *onenand_base, int *freq_ptr)
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = gpmc_cs_set_timings(gpmc_onenand_data->cs, &t);
> +	ret = gpmc_cs_set_timings(gpmc_onenand_data->cs, &t, &onenand_sync);
>  	if (ret < 0)
>  		return ret;
>  
> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> index a6abaf0..9cf8d21 100644
> --- a/drivers/memory/omap-gpmc.c
> +++ b/drivers/memory/omap-gpmc.c
> @@ -139,6 +139,8 @@
>  #define GPMC_CONFIG1_WAIT_READ_MON      (1 << 22)
>  #define GPMC_CONFIG1_WAIT_WRITE_MON     (1 << 21)
>  #define GPMC_CONFIG1_WAIT_MON_IIME(val) ((val & 3) << 18)

Not caused by your patch but we can fix the typo

GPMC_CONFIG1_WAIT_MON_IIME -> GPMC_CONFIG1_WAIT_MON_TIME

> +/** WAITMONITORINGTIME Max Ticks */
> +#define GPMC_CONFIG1_WAIT_MON_TIME_MAX  2
>  #define GPMC_CONFIG1_WAIT_PIN_SEL(val)  ((val & 3) << 16)
>  #define GPMC_CONFIG1_DEVICESIZE(val)    ((val & 3) << 12)
>  #define GPMC_CONFIG1_DEVICESIZE_16      GPMC_CONFIG1_DEVICESIZE(1)
> @@ -511,13 +513,41 @@ static int set_gpmc_timing_reg(int cs, int reg, int st_bit, int end_bit,
>  			t->field, #field) < 0)			\
>  		return -1
>  
> +/**
> + * gpmc_calc_waitmonitoring_divider - calculate proper GPMCFCLKDIVIDER based on WAITMONITORINGTIME
> + * @wait_monitoring WAITMONITORINGTIME in ns.
> + * @return          -1 on failure to scale, else proper divider > 0.
> + * @note            WAITMONITORINGTIME will be _at least_ as long as desired.
> + *                  i.e. read timings should be kept            -> don't sample bus too early
> + *                  while write timings should work out as well -> data is longer on bus
> + */
> +static int gpmc_calc_waitmonitoring_divider(unsigned int wait_monitoring)
> +{
> +
> +	int div = gpmc_ns_to_ticks(wait_monitoring);
> +
> +	div += GPMC_CONFIG1_WAIT_MON_TIME_MAX - 1;
> +	div /= GPMC_CONFIG1_WAIT_MON_TIME_MAX;

Sorry I didn't understand how this works. :P
>From the TRM,

waitmonitoringtime_ns = waitmonitoring_ticks x (gpmc_clk_div + 1) x gpmc_fclk_ns

> +
> +	if (div > 4)
> +		return -1;
> +	if (div <= 0)
> +		div = 1;
> +
> +	return div;
> +
> +}
> +
> +/**
> + * gpmc_calc_divider - calculate GPMC_FCLK divider for sync_clk GPMC_CLK period.
> + * @sync_clk GPMC_CLK period in ps.
> + * @return   Returns at least 1 if GPMC_FCLK can be divided to GPMC_CLK.
> + *           Else, returns -1.
> + */
>  int gpmc_calc_divider(unsigned int sync_clk)
>  {
> -	int div;
> -	u32 l;
> +	int div = gpmc_ps_to_ticks(sync_clk);
>  
> -	l = sync_clk + (gpmc_get_fclk_period() - 1);
> -	div = l / gpmc_get_fclk_period();
>  	if (div > 4)
>  		return -1;
>  	if (div <= 0)
> @@ -526,7 +556,13 @@ int gpmc_calc_divider(unsigned int sync_clk)
>  	return div;
>  }
>  
> -int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t)
> +/**
> + * gpmc_cs_set_timings - program timing parameters for Chip Select Region.
> + * @cs   Chip Select Region.
> + * @t    GPMC timing parameters.
> + * @s    GPMC timing settings.
> + */
> +int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t, const struct gpmc_settings *s)
>  {
>  	int div;
>  	u32 l;
> @@ -536,6 +572,32 @@ int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t)
>  	if (div < 0)
>  		return div;
>  
> +	/* 
> +	 * See if we need to change the divider for waitmonitoringtime.
> +	 * 
> +	 * If DT contains sync-clk-ps for truly asynchronous accesses,
> +	 * ignore it as long as waitmonitoringtime is used.
> +	 * 

The comment in the $subject was more easier to understand for me than the above

"Calculate GPMCFCLKDIVIDER independent of gpmc,sync-clk-ps in DT for
truly asynchronous accesses, i.e. both read and write asynchronous."

> +	 * This protects mixed synchronous and asynchronous devices,
> +	 * i.e. must not change div to scale async waitmonitoringtime or
> +	 * sync accesses would be broken.
> +	 * 
> +	 * We raise an error later if waitmonitoringtime does not fit.
> +	 */
> +	if (!s->sync_read && !s->sync_write &&
> +	    (s->wait_on_read || s->wait_on_write)
> +	   ) {
> +
> +		div = gpmc_calc_waitmonitoring_divider(t->wait_monitoring);
> +		if (div < 0) {
> +			pr_err("%s: waitmonitoringtime %3d ns too large for greatest gpmcfclkdivider.\n",
> +			       __func__,
> +			       t->wait_monitoring
> +			       );
> +			return -1;
> +		}
> +	}
> +
>  	GPMC_SET_ONE(GPMC_CS_CONFIG2,  0,  3, cs_on);
>  	GPMC_SET_ONE(GPMC_CS_CONFIG2,  8, 12, cs_rd_off);
>  	GPMC_SET_ONE(GPMC_CS_CONFIG2, 16, 20, cs_wr_off);
> @@ -1793,7 +1855,7 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
>  	if (ret < 0)
>  		goto err;
>  
> -	ret = gpmc_cs_set_timings(cs, &gpmc_t);
> +	ret = gpmc_cs_set_timings(cs, &gpmc_t, &gpmc_s);
>  	if (ret) {
>  		dev_err(&pdev->dev, "failed to set gpmc timings for: %s\n",
>  			child->name);
> diff --git a/include/linux/omap-gpmc.h b/include/linux/omap-gpmc.h
> index c2080ee..9301437 100644
> --- a/include/linux/omap-gpmc.h
> +++ b/include/linux/omap-gpmc.h
> @@ -163,7 +163,7 @@ extern unsigned int gpmc_ticks_to_ns(unsigned int ticks);
>  
>  extern void gpmc_cs_write_reg(int cs, int idx, u32 val);
>  extern int gpmc_calc_divider(unsigned int sync_clk);
> -extern int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t);
> +extern int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t, const struct gpmc_settings *s);
>  extern int gpmc_cs_program_settings(int cs, struct gpmc_settings *p);
>  extern int gpmc_cs_request(int cs, unsigned long size, unsigned long *base);
>  extern void gpmc_cs_free(int cs);
> 

cheers,
-roger