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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43277b0efefsm37804809f8f.25.2025.12.30.15.23.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Dec 2025 15:23:58 -0800 (PST) Date: Tue, 30 Dec 2025 23:23:57 +0000 From: David Laight To: SeungJu Cheon Cc: ray.huang@amd.com, linux@roeck-us.net, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hwmon:fam15h_power Use div64_u64() for 64-bit divisor Message-ID: <20251230232357.00222b64@pumpkin> In-Reply-To: <20251230120959.199139-1-suunj1331@gmail.com> References: <20251230120959.199139-1-suunj1331@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 30 Dec 2025 21:09:59 +0900 SeungJu Cheon wrote: > tdelta is u64, but do_div() truncates the divisor to 32 bits. > Use div64_u64() to handle the full 64-bit divisor correctly. Looking at the code I think that tdelta is a time interval and will always fit in 32bits - so the code is probably fine. Also I can't see anything that requires jdelta[] be an array. Neither can I see the justification for MAX_CUS being 8. > > Signed-off-by: SeungJu Cheon > --- > drivers/hwmon/fam15h_power.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c > index 8ecebea53651..5e3692606516 100644 > --- a/drivers/hwmon/fam15h_power.c > +++ b/drivers/hwmon/fam15h_power.c > @@ -241,7 +241,7 @@ static ssize_t power1_average_show(struct device *dev, > } > tdelta = data->cpu_sw_pwr_ptsc[cu] - prev_ptsc[cu]; > jdelta[cu] *= data->cpu_pwr_sample_ratio * 1000; > - do_div(jdelta[cu], tdelta); > + jdelta[cu] = div64_u64(jdelta[cu], tdelta); > > /* the unit is microWatt */ > avg_acc += jdelta[cu]; That could be: jdelta *= data->cpu_pwr_sample_ratio * 1000; avg_acc += div64_u64(jdelta, tdelta); (or even 1 line...) David