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[217.31.177.236]) by smtp.gmail.com with ESMTPSA id s7sm1035389lji.26.2019.08.30.14.42.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Aug 2019 14:42:20 -0700 (PDT) Date: Fri, 30 Aug 2019 23:42:19 +0200 From: Niklas =?iso-8859-1?Q?S=F6derlund?= To: Geert Uytterhoeven Cc: Michael Turquette , Stephen Boyd , linux-clk@vger.kernel.org, linux-renesas-soc@vger.kernel.org Subject: Re: [PATCH v2 1/8] clk: renesas: rcar-gen2: Improve arithmetic divisions Message-ID: <20190830214219.GQ8479@bigcity.dyn.berto.se> References: <20190830134515.11925-1-geert+renesas@glider.be> <20190830134515.11925-2-geert+renesas@glider.be> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190830134515.11925-2-geert+renesas@glider.be> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-clk-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org Hi Geert, Thanks for your work. On 2019-08-30 15:45:08 +0200, Geert Uytterhoeven wrote: > - Use div64_ul() instead of div_u64() if the divisor is unsigned long, > to avoid truncation to 32-bit on 64-bit platforms, > - Prefer ULL constant suffixes over casts to u64, > - Prioritize multiplication over division, to increase accuracy. > > Signed-off-by: Geert Uytterhoeven Reviewed-by: Niklas Söderlund > --- > v2: > - New. > --- > drivers/clk/renesas/rcar-gen2-cpg.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/clk/renesas/rcar-gen2-cpg.c b/drivers/clk/renesas/rcar-gen2-cpg.c > index f596a2dafcf4d8d1..c378505830f0bacc 100644 > --- a/drivers/clk/renesas/rcar-gen2-cpg.c > +++ b/drivers/clk/renesas/rcar-gen2-cpg.c > @@ -72,10 +72,10 @@ static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate, > if (!prate) > prate = 1; > > - mult = div_u64((u64)rate * 32, prate); > + mult = div64_ul(rate * 32ULL, prate); > mult = clamp(mult, 1U, 32U); > > - return *parent_rate / 32 * mult; > + return div_u64((u64)*parent_rate * mult, 32); > } > > static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate, > @@ -86,7 +86,7 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate, > u32 val, kick; > unsigned int i; > > - mult = div_u64((u64)rate * 32, parent_rate); > + mult = div64_ul(rate * 32ULL, parent_rate); > mult = clamp(mult, 1U, 32U); > > if (readl(zclk->kick_reg) & CPG_FRQCRB_KICK) > -- > 2.17.1 > -- Regards, Niklas Söderlund