From: William Qiu <william.qiu@starfivetech.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-riscv@lists.infradead.org>, <linux-pwm@vger.kernel.org>,
"Emil Renner Berthing" <kernel@esmil.dk>,
Rob Herring <robh+dt@kernel.org>,
Thierry Reding <thierry.reding@gmail.com>,
Philipp Zabel <p.zabel@pengutronix.de>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
Conor Dooley <conor+dt@kernel.org>,
Hal Feng <hal.feng@starfivetech.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>
Subject: Re: [PATCH v6 2/4] pwm: opencores: Add PWM driver support
Date: Wed, 1 Nov 2023 10:22:44 +0800 [thread overview]
Message-ID: <7d64ea1d-b573-4a69-ba0c-4cbfab638c5e@starfivetech.com> (raw)
In-Reply-To: <20231020112539.gctx5uj2rrhryulo@pengutronix.de>
On 2023/10/20 19:25, Uwe Kleine-König wrote:
>> + void __iomem *base = pwm->data->get_ch_base ?
>> + pwm->data->get_ch_base(pwm->regs, dev->hwpwm) : pwm->regs;
>> + u32 period_data, duty_data, ctrl_data;
>> +
>> + period_data = readl(REG_OCPWM_LRC(base));
>> + duty_data = readl(REG_OCPWM_HRC(base));
>> + ctrl_data = readl(REG_OCPWM_CTRL(base));
>> +
>> + state->period = DIV_ROUND_CLOSEST_ULL((u64)period_data * NSEC_PER_SEC, pwm->clk_rate);
>> + state->duty_cycle = DIV_ROUND_CLOSEST_ULL((u64)duty_data * NSEC_PER_SEC, pwm->clk_rate);
>
> Please test your driver with PWM_DEBUG enabled. The rounding is wrong
> here.
>
Hi Uwe,
The conclusion after checking is: when the period or duty_cycle value set
by the user is not divisible (1000000000/49.5M), there will be an error.
This error is due to hardware accuracy. So why is rounding is wrong?
rockchip also has a similar implementation drivers/pwm/ pwm-rockchip.c
Best regards,
William
next prev parent reply other threads:[~2023-11-01 2:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-20 10:37 [PATCH v6 0/4] StarFive's Pulse Width Modulation driver support William Qiu
2023-10-20 10:37 ` [PATCH v6 1/4] dt-bindings: pwm: Add OpenCores PWM module William Qiu
2023-10-20 14:21 ` Conor Dooley
2023-10-20 14:22 ` Conor Dooley
2023-10-20 18:04 ` Krzysztof Kozlowski
2023-10-23 8:00 ` William Qiu
2023-10-20 18:01 ` Krzysztof Kozlowski
2023-10-23 8:02 ` William Qiu
2023-10-20 10:37 ` [PATCH v6 2/4] pwm: opencores: Add PWM driver support William Qiu
2023-10-20 11:25 ` Uwe Kleine-König
2023-10-24 9:16 ` William Qiu
2023-10-24 11:45 ` Uwe Kleine-König
2023-10-27 10:23 ` William Qiu
2023-10-27 13:23 ` Uwe Kleine-König
2023-11-01 2:22 ` William Qiu [this message]
2023-11-02 11:30 ` Uwe Kleine-König
2023-11-06 7:26 ` William Qiu
2023-10-20 10:37 ` [PATCH v6 3/4] riscv: dts: starfive: jh7110: Add PWM node and pins configuration William Qiu
2023-10-25 13:45 ` Emil Renner Berthing
2023-10-20 10:37 ` [PATCH v6 4/4] riscv: dts: starfive: jh7100: " William Qiu
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