From: Guru Das Srinagesh <gurus@codeaurora.org> To: linux-pwm@vger.kernel.org, "Thierry Reding" <thierry.reding@gmail.com>, "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de> Cc: Subbaraman Narayanamurthy <subbaram@codeaurora.org>, David Collins <collinsd@codeaurora.org>, linux-kernel@vger.kernel.org, Joe Perches <joe@perches.com>, Stephen Boyd <sboyd@kernel.org>, Lee Jones <lee.jones@linaro.org>, Arnd Bergmann <arnd@arndb.de>, Geert Uytterhoeven <geert@linux-m68k.org>, Guenter Roeck <linux@roeck-us.net>, Daniel Thompson <daniel.thompson@linaro.org>, Dan Carpenter <dan.carpenter@oracle.com>, linux-arm-kernel@lists.infradead.org, Guru Das Srinagesh <gurus@codeaurora.org>, Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix Kernel Team <kernel@pengutronix.de>, Fabio Estevam <festevam@gmail.com>, NXP Linux Team <linux-imx@nxp.com> Subject: [RESEND PATCH v14 06/11] pwm: imx27: Use 64-bit division macro and function Date: Tue, 12 May 2020 17:39:40 -0700 [thread overview] Message-ID: <de0bebdbfffd28c87f50bb6ef1751d352fb960a2.1589330178.git.gurus@codeaurora.org> (raw) In-Reply-To: <cover.1589330178.git.gurus@codeaurora.org> In-Reply-To: <cover.1589330178.git.gurus@codeaurora.org> Since the PWM framework is switching struct pwm_state.period's datatype to u64, prepare for this transition by using DIV_ROUND_UP_ULL to handle a 64-bit dividend, and div64_u64 to handle a 64-bit divisor. Also handle a possible overflow in the calculation of period_cycles when both clk_rate and period are large numbers. This logic was unit-tested out by calculating period_cycles using both the existing logic and the proposed one, and the results are as below. ---------------------------------------------------------------------------- clk_rate period existing proposed ---------------------------------------------------------------------------- 1000000000 18446744073709551615 18446744072 18446744073000000000 (U64_MAX) ---------------------------------------------------------------------------- 1000000000 4294967291 4294967291 4294967291 ---------------------------------------------------------------------------- Overflow occurs in the first case with the existing logic, whereas the proposed logic handles it better, sacrificing some precision in a best-effort attempt to handle overflow. As for the second case where there are more typical values of period, the proposed logic handles that correctly too. Cc: Shawn Guo <shawnguo@kernel.org> Cc: Sascha Hauer <s.hauer@pengutronix.de> Cc: Pengutronix Kernel Team <kernel@pengutronix.de> Cc: Fabio Estevam <festevam@gmail.com> Cc: NXP Linux Team <linux-imx@nxp.com> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org> --- drivers/pwm/pwm-imx27.c | 53 +++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 45 insertions(+), 8 deletions(-) diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c index a6e40d4..164cb65 100644 --- a/drivers/pwm/pwm-imx27.c +++ b/drivers/pwm/pwm-imx27.c @@ -203,7 +203,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip, sr = readl(imx->mmio_base + MX3_PWMSR); fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr); if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) { - period_ms = DIV_ROUND_UP(pwm_get_period(pwm), + period_ms = DIV_ROUND_UP_ULL(pwm_get_period(pwm), NSEC_PER_MSEC); msleep(period_ms); @@ -213,6 +213,45 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip, } } +static int pwm_imx27_calc_period_cycles(const struct pwm_state *state, + unsigned long clk_rate, + unsigned long *period_cycles) +{ + u64 c = 0, c1, c2; + + c1 = clk_rate; + c2 = state->period; + if (c2 > c1) { + c2 = c1; + c1 = state->period; + } + + if (!c1 || !c2) { + pr_err("clk rate and period should be nonzero\n"); + return -EINVAL; + } + + if (c2 <= div64_u64(U64_MAX, c1)) { + c = c1 * c2; + do_div(c, 1000000000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000))) { + do_div(c1, 1000); + c = c1 * c2; + do_div(c, 1000000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000))) { + do_div(c1, 1000000); + c = c1 * c2; + do_div(c, 1000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000000))) { + do_div(c1, 1000000000); + c = c1 * c2; + } + + *period_cycles = c; + + return 0; +} + static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, const struct pwm_state *state) { @@ -225,18 +264,16 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, pwm_get_state(pwm, &cstate); - c = clk_get_rate(imx->clk_per); - c *= state->period; - - do_div(c, 1000000000); - period_cycles = c; + ret = pwm_imx27_calc_period_cycles(state, clk_get_rate(imx->clk_per), + &period_cycles); + if (ret) + return ret; prescale = period_cycles / 0x10000 + 1; period_cycles /= prescale; c = (unsigned long long)period_cycles * state->duty_cycle; - do_div(c, state->period); - duty_cycles = c; + duty_cycles = div64_u64(c, state->period); /* * according to imx pwm RM, the real period value should be PERIOD -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
WARNING: multiple messages have this Message-ID (diff)
From: Guru Das Srinagesh <gurus@codeaurora.org> To: linux-pwm@vger.kernel.org, "Thierry Reding" <thierry.reding@gmail.com>, "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de> Cc: Subbaraman Narayanamurthy <subbaram@codeaurora.org>, David Collins <collinsd@codeaurora.org>, linux-kernel@vger.kernel.org, Joe Perches <joe@perches.com>, Stephen Boyd <sboyd@kernel.org>, Lee Jones <lee.jones@linaro.org>, Arnd Bergmann <arnd@arndb.de>, Geert Uytterhoeven <geert@linux-m68k.org>, Guenter Roeck <linux@roeck-us.net>, Daniel Thompson <daniel.thompson@linaro.org>, Dan Carpenter <dan.carpenter@oracle.com>, linux-arm-kernel@lists.infradead.org, Guru Das Srinagesh <gurus@codeaurora.org>, Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix Kernel Team <kernel@pengutronix.de>, Fabio Estevam <festevam@gmail.com>, NXP Linux Team <linux-imx@nxp.com> Subject: [RESEND PATCH v14 06/11] pwm: imx27: Use 64-bit division macro and function Date: Wed, 20 May 2020 15:55:59 -0700 [thread overview] Message-ID: <de0bebdbfffd28c87f50bb6ef1751d352fb960a2.1589330178.git.gurus@codeaurora.org> (raw) Message-ID: <20200520225559.ClfHZLsodWFckCoWNYqWmbORislB5Lp7xdVNzj7xnuI@z> (raw) In-Reply-To: <cover.1589330178.git.gurus@codeaurora.org> In-Reply-To: <cover.1589330178.git.gurus@codeaurora.org> Since the PWM framework is switching struct pwm_state.period's datatype to u64, prepare for this transition by using DIV_ROUND_UP_ULL to handle a 64-bit dividend, and div64_u64 to handle a 64-bit divisor. Also handle a possible overflow in the calculation of period_cycles when both clk_rate and period are large numbers. This logic was unit-tested out by calculating period_cycles using both the existing logic and the proposed one, and the results are as below. ---------------------------------------------------------------------------- clk_rate period existing proposed ---------------------------------------------------------------------------- 1000000000 18446744073709551615 18446744072 18446744073000000000 (U64_MAX) ---------------------------------------------------------------------------- 1000000000 4294967291 4294967291 4294967291 ---------------------------------------------------------------------------- Overflow occurs in the first case with the existing logic, whereas the proposed logic handles it better, sacrificing some precision in a best-effort attempt to handle overflow. As for the second case where there are more typical values of period, the proposed logic handles that correctly too. Cc: Shawn Guo <shawnguo@kernel.org> Cc: Sascha Hauer <s.hauer@pengutronix.de> Cc: Pengutronix Kernel Team <kernel@pengutronix.de> Cc: Fabio Estevam <festevam@gmail.com> Cc: NXP Linux Team <linux-imx@nxp.com> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org> --- drivers/pwm/pwm-imx27.c | 53 +++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 45 insertions(+), 8 deletions(-) diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c index a6e40d4..164cb65 100644 --- a/drivers/pwm/pwm-imx27.c +++ b/drivers/pwm/pwm-imx27.c @@ -203,7 +203,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip, sr = readl(imx->mmio_base + MX3_PWMSR); fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr); if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) { - period_ms = DIV_ROUND_UP(pwm_get_period(pwm), + period_ms = DIV_ROUND_UP_ULL(pwm_get_period(pwm), NSEC_PER_MSEC); msleep(period_ms); @@ -213,6 +213,45 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip, } } +static int pwm_imx27_calc_period_cycles(const struct pwm_state *state, + unsigned long clk_rate, + unsigned long *period_cycles) +{ + u64 c = 0, c1, c2; + + c1 = clk_rate; + c2 = state->period; + if (c2 > c1) { + c2 = c1; + c1 = state->period; + } + + if (!c1 || !c2) { + pr_err("clk rate and period should be nonzero\n"); + return -EINVAL; + } + + if (c2 <= div64_u64(U64_MAX, c1)) { + c = c1 * c2; + do_div(c, 1000000000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000))) { + do_div(c1, 1000); + c = c1 * c2; + do_div(c, 1000000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000))) { + do_div(c1, 1000000); + c = c1 * c2; + do_div(c, 1000); + } else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000000))) { + do_div(c1, 1000000000); + c = c1 * c2; + } + + *period_cycles = c; + + return 0; +} + static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, const struct pwm_state *state) { @@ -225,18 +264,16 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, pwm_get_state(pwm, &cstate); - c = clk_get_rate(imx->clk_per); - c *= state->period; - - do_div(c, 1000000000); - period_cycles = c; + ret = pwm_imx27_calc_period_cycles(state, clk_get_rate(imx->clk_per), + &period_cycles); + if (ret) + return ret; prescale = period_cycles / 0x10000 + 1; period_cycles /= prescale; c = (unsigned long long)period_cycles * state->duty_cycle; - do_div(c, state->period); - duty_cycles = c; + duty_cycles = div64_u64(c, state->period); /* * according to imx pwm RM, the real period value should be PERIOD -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2020-05-13 0:39 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-13 0:39 [RESEND PATCH v14 00/11] Convert PWM period and duty cycle to u64 Guru Das Srinagesh 2020-05-04 18:50 ` Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 01/11] drm/i915: Use 64-bit division macro Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 02/11] hwmon: pwm-fan: " Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 03/11] ir-rx51: " Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 04/11] pwm: clps711x: Cast period to u32 before use as divisor Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 05/11] pwm: pwm-imx-tpm: Use 64-bit division macro Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 06/11] pwm: imx27: Use 64-bit division macro and function Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 07/11] pwm: sifive: Use 64-bit division macro Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 08/11] pwm: sun4i: Use nsecs_to_jiffies to avoid a division Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 09/11] backlight: pwm_bl: Use 64-bit division function Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 10/11] clk: pwm: " Guru Das Srinagesh 2020-05-04 18:50 ` [RESEND PATCH v14 11/11] pwm: core: Convert period and duty cycle to u64 Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 00/11] Convert PWM " Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 01/11] drm/i915: Use 64-bit division macro Guru Das Srinagesh 2020-05-20 22:55 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 02/11] hwmon: pwm-fan: " Guru Das Srinagesh 2020-05-20 22:55 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 03/11] ir-rx51: " Guru Das Srinagesh 2020-05-20 22:55 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 04/11] pwm: clps711x: Cast period to u32 before use as divisor Guru Das Srinagesh 2020-05-20 22:55 ` Guru Das Srinagesh 2020-05-21 10:19 ` Daniel Thompson 2020-05-21 20:25 ` Guru Das Srinagesh 2020-05-22 9:37 ` Daniel Thompson 2020-05-22 23:19 ` Guru Das Srinagesh 2020-05-23 17:08 ` Daniel Thompson 2020-05-13 0:39 ` [RESEND PATCH v14 05/11] pwm: pwm-imx-tpm: Use 64-bit division macro Guru Das Srinagesh 2020-05-20 22:55 ` Guru Das Srinagesh 2020-05-13 0:39 ` Guru Das Srinagesh [this message] 2020-05-20 22:55 ` [RESEND PATCH v14 06/11] pwm: imx27: Use 64-bit division macro and function Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 07/11] pwm: sifive: Use 64-bit division macro Guru Das Srinagesh 2020-05-20 22:56 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 08/11] pwm: sun4i: Use nsecs_to_jiffies to avoid a division Guru Das Srinagesh 2020-05-20 22:56 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 09/11] backlight: pwm_bl: Use 64-bit division function Guru Das Srinagesh 2020-05-20 22:56 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 10/11] clk: pwm: " Guru Das Srinagesh 2020-05-20 22:56 ` Guru Das Srinagesh 2020-05-13 0:39 ` [RESEND PATCH v14 11/11] pwm: core: Convert period and duty cycle to u64 Guru Das Srinagesh 2020-05-20 22:56 ` Guru Das Srinagesh 2020-05-20 22:55 ` [RESEND PATCH v14 00/11] Convert PWM " Guru Das Srinagesh
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=de0bebdbfffd28c87f50bb6ef1751d352fb960a2.1589330178.git.gurus@codeaurora.org \ --to=gurus@codeaurora.org \ --cc=arnd@arndb.de \ --cc=collinsd@codeaurora.org \ --cc=dan.carpenter@oracle.com \ --cc=daniel.thompson@linaro.org \ --cc=festevam@gmail.com \ --cc=geert@linux-m68k.org \ --cc=joe@perches.com \ --cc=kernel@pengutronix.de \ --cc=lee.jones@linaro.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-imx@nxp.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-pwm@vger.kernel.org \ --cc=linux@roeck-us.net \ --cc=s.hauer@pengutronix.de \ --cc=sboyd@kernel.org \ --cc=shawnguo@kernel.org \ --cc=subbaram@codeaurora.org \ --cc=thierry.reding@gmail.com \ --cc=u.kleine-koenig@pengutronix.de \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).