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Subject: Re: [PATCH 1/3] clk: tegra: refactor 7.1 div calculation
To:     Aapo Vienamo <avienamo@nvidia.com>,
        Peter De Schrijver <pdeschrijver@nvidia.com>
Cc:     Prashant Gaikwad <pgaikwad@nvidia.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
        linux-tegra@vger.kernel.org
References: <1530617721-5767-1-git-send-email-avienamo@nvidia.com>
From:   Peter Geis <pgwipeout@gmail.com>
Message-ID: <46bc7178-f8a4-cc4e-ebe3-507671ffb735@gmail.com>
Date:   Tue, 3 Jul 2018 11:10:21 -0400
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Good Morning,

Just a heads up.
During compilation with your patches, I get the following warning:

In file included from ./arch/arm/include/asm/div64.h:127:0,
                  from ./include/linux/kernel.h:174,
                  from drivers/clk/tegra/div71.c:17:
drivers/clk/tegra/div71.c: In function ‘div71_get’:
./include/asm-generic/div64.h:222:28: warning: comparison of distinct 
pointer types lacks a cast
   (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                             ^
drivers/clk/tegra/div71.c:40:2: note: in expansion of macro ‘do_div’
   do_div(divider_ux1, rate);
   ^~~~~~

Very Respectfully,
Peter Geis


On 07/03/2018 07:35 AM, Aapo Vienamo wrote:
> From: Peter De Schrijver <pdeschrijver@nvidia.com>
> 
> Move this to a separate file so it can be used to calculate the sdmmc
> clock dividers.
> 
> Signed-off-by: Peter De-Schrijver <pdeschrijver@nvidia.com>
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> ---
>   drivers/clk/tegra/Makefile      |  1 +
>   drivers/clk/tegra/clk-divider.c | 30 ++++--------------------
>   drivers/clk/tegra/clk.h         |  3 +++
>   drivers/clk/tegra/div71.c       | 51 +++++++++++++++++++++++++++++++++++++++++
>   4 files changed, 60 insertions(+), 25 deletions(-)
>   create mode 100644 drivers/clk/tegra/div71.c
> 
> diff --git a/drivers/clk/tegra/Makefile b/drivers/clk/tegra/Makefile
> index b716923..6d4f563 100644
> --- a/drivers/clk/tegra/Makefile
> +++ b/drivers/clk/tegra/Makefile
> @@ -24,3 +24,4 @@ obj-$(CONFIG_ARCH_TEGRA_132_SOC)	+= clk-tegra124.o
>   obj-y					+= cvb.o
>   obj-$(CONFIG_ARCH_TEGRA_210_SOC)	+= clk-tegra210.o
>   obj-$(CONFIG_CLK_TEGRA_BPMP)		+= clk-bpmp.o
> +obj-y					+= div71.o
> diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c
> index 16e0aee..ad87858 100644
> --- a/drivers/clk/tegra/clk-divider.c
> +++ b/drivers/clk/tegra/clk-divider.c
> @@ -32,35 +32,15 @@
>   static int get_div(struct tegra_clk_frac_div *divider, unsigned long rate,
>   		   unsigned long parent_rate)
>   {
> -	u64 divider_ux1 = parent_rate;
> -	u8 flags = divider->flags;
> -	int mul;
> -
> -	if (!rate)
> -		return 0;
> -
> -	mul = get_mul(divider);
> -
> -	if (!(flags & TEGRA_DIVIDER_INT))
> -		divider_ux1 *= mul;
> -
> -	if (flags & TEGRA_DIVIDER_ROUND_UP)
> -		divider_ux1 += rate - 1;
> -
> -	do_div(divider_ux1, rate);
> -
> -	if (flags & TEGRA_DIVIDER_INT)
> -		divider_ux1 *= mul;
> +	int div;
>   
> -	divider_ux1 -= mul;
> +	div = div71_get(rate, parent_rate, divider->width, divider->frac_width,
> +			divider->flags);
>   
> -	if ((s64)divider_ux1 < 0)
> +	if (div < 0)
>   		return 0;
>   
> -	if (divider_ux1 > get_max_div(divider))
> -		return get_max_div(divider);
> -
> -	return divider_ux1;
> +	return div;
>   }
>   
>   static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw,
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index e1f8846..f14e136 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -811,6 +811,9 @@ extern tegra_clk_apply_init_table_func tegra_clk_apply_init_table;
>   int tegra_pll_wait_for_lock(struct tegra_clk_pll *pll);
>   u16 tegra_pll_get_fixed_mdiv(struct clk_hw *hw, unsigned long input_rate);
>   int tegra_pll_p_div_to_hw(struct tegra_clk_pll *pll, u8 p_div);
> +int div71_get(unsigned long rate, unsigned parent_rate, u8 width,
> +	      u8 frac_width, u8 flags);
> +
>   
>   /* Combined read fence with delay */
>   #define fence_udelay(delay, reg)	\
> diff --git a/drivers/clk/tegra/div71.c b/drivers/clk/tegra/div71.c
> new file mode 100644
> index 0000000..27b3846
> --- /dev/null
> +++ b/drivers/clk/tegra/div71.c
> @@ -0,0 +1,51 @@
> +/*
> + * Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/kernel.h>
> +
> +#include "clk.h"
> +
> +#define div_mask(w) ((1 << (w)) - 1)
> +
> +int div71_get(unsigned long rate, unsigned parent_rate, u8 width,
> +	      u8 frac_width, u8 flags)
> +{
> +	s64 divider_ux1 = parent_rate;
> +	int mul;
> +
> +	if (!rate)
> +		return 0;
> +
> +	mul = 1 << frac_width;
> +
> +	if (!(flags & TEGRA_DIVIDER_INT))
> +		divider_ux1 *= mul;
> +
> +	if (flags & TEGRA_DIVIDER_ROUND_UP)
> +		divider_ux1 += rate - 1;
> +
> +	do_div(divider_ux1, rate);
> +
> +	if (flags & TEGRA_DIVIDER_INT)
> +		divider_ux1 *= mul;
> +
> +	divider_ux1 -= mul;
> +
> +	if (divider_ux1 > div_mask(width))
> +		return div_mask(width);
> +
> +	return divider_ux1;
> +}
>