linux-kernel - Re: [PATCH 4/8] ARM OMAP2+ GPMC: change get_gpmc_timing

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Date:	Fri, 27 Feb 2015 12:43:54 +0200
From:	Roger Quadros <rogerq@...com>
To:	Robert ABEL <rabel@...-ec.uni-bielefeld.de>, <balbi@...com>,
	<linux-omap@...r.kernel.org>
CC:	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<tony@...mide.com>, <linux@....linux.org.uk>
Subject: Re: [PATCH 4/8] ARM OMAP2+ GPMC: change get_gpmc_timing_reg output
 for DTS

Robert,

On 26/02/15 16:45, Robert ABEL wrote:
> DTS output was formatted to require additional work when copy-pasting into DTS.
> Nano-second timings were replaced with interval of values that produce the same
> number of clock ticks.
> 
> Signed-off-by: Robert ABEL <rabel@...-ec.uni-bielefeld.de>
> ---
>  drivers/memory/omap-gpmc.c | 35 ++++++++++++++++++++++++++---------
>  1 file changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> index dbb6753..9340e7a 100644
> --- a/drivers/memory/omap-gpmc.c
> +++ b/drivers/memory/omap-gpmc.c
> @@ -337,32 +337,49 @@ static void gpmc_cs_bool_timings(int cs, const struct gpmc_bool_timings *p)
>  }
>  
>  #ifdef DEBUG
> +/**
> + * get_gpmc_timing_reg - read a timing parameter and print DTS settings for it.
> + * @cs      Chip Select Region
> + * @reg     GPMC_CS_CONFIGn register offset.
> + * @st_bit  Start Bit
> + * @end_bit End Bit. Must be >= @st_bit.
> + * @name    DTS node name, w/o "gpmc,"
> + * @raw     Raw Format Option.
> + *          raw format:  gpmc,name = <value>
> + *          tick format: gpmc,name = <value> /&zwj;*(x ns -- y ns]; x ticks *&zwj;/
> + *          Where (x ns -- y ns] is the half-open interval from x ns to y ns that
> + *          result in the same tick value.
> + * @noval   Parameter values equal to 0 are not printed.
> + * @shift   Parameter value left shifts @shift, which is then printed instead of value.
> + *
> + */
>  static int get_gpmc_timing_reg(int cs, int reg, int st_bit, int end_bit,
>  			       bool raw, bool noval, int shift,
>  			       const char *name)
>  {
>  	u32 l;
> -	int nr_bits, max_value, mask;
> +	int nr_bits;
> +	int mask;
>  
>  	l = gpmc_cs_read_reg(cs, reg);
>  	nr_bits = end_bit - st_bit + 1;
> -	max_value = (1 << nr_bits) - 1;
> -	mask = max_value << st_bit;
> -	l = (l & mask) >> st_bit;
> +	mask = (1 << nr_bits) - 1;
> +	l = (l >> st_bit) & mask;
>  	if (shift)
>  		l = (shift << l);
>  	if (noval && (l == 0))
>  		return 0;
>  	if (!raw) {
> -		unsigned int time_ns_min, time_ns, time_ns_max;
> +		/* DTS tick format for timings in ns */
> +		unsigned int time_ns;
> +		unsigned int time_ns_min;
>  
>  		time_ns_min = gpmc_ticks_to_ns(l ? l - 1 : 0);

should be
		time_ns_min = l ? gpmc_ticks_to_ns(l - 1) + 1 : 0;

		+ 1ns since we don't want to fall into the previous tick bracket.
		for l == 0 we have t_min as 0. no need to pass it through gpmc_ticks_to_ns() or add 1 ns.

>  		time_ns = gpmc_ticks_to_ns(l);
> -		time_ns_max = gpmc_ticks_to_ns(l + 1 > max_value ?
> -					       max_value : l + 1);
> -		pr_info("gpmc,%s = <%u> (%u - %u ns, %i ticks)\n",
> -			name, time_ns, time_ns_min, time_ns_max, l);
> +		pr_info("gpmc,%s = <%u> /* (%u ns - %u ns]; %i ticks */\n",
> +			name, time_ns, time_ns_min, time_ns, l);
>  	} else {
> +		/* raw format */
>  		pr_info("gpmc,%s = <%u>\n", name, l);
>  	}
>  
> 
cheers,
-roger
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