From patchwork Thu Aug 13 12:48:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Walle X-Patchwork-Id: 254622 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C6AAC433E5 for ; Thu, 13 Aug 2020 12:50:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2C4020866 for ; Thu, 13 Aug 2020 12:50:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="PDCSFBnL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726704AbgHMMuJ (ORCPT ); Thu, 13 Aug 2020 08:50:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726591AbgHMMs4 (ORCPT ); Thu, 13 Aug 2020 08:48:56 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56627C061383; Thu, 13 Aug 2020 05:48:55 -0700 (PDT) Received: from mwalle01.sab.local. (unknown [213.135.10.150]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 821AD23E46; Thu, 13 Aug 2020 14:48:53 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1597322933; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W+32geYoPc27uiAHc5NIXXOOS091TcExk3j1uDs2c+U=; b=PDCSFBnLGZRFT5CFA4rAJsnzDQi3oWMmcvwttpU+WUO7YvMbfzhDIov/iPa1Dqxvepgwk5 /F1VKyfJEcXeNXpF5Ga3QIqyc+CfSKFAqy5XPs5jm6Tp/SZ0cvozETqcW1VAN+t5w8uXLq gDXQkxfeS6wX2FiBbwDEvEQ469pAocQ= From: Michael Walle To: linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Linus Walleij , Bartosz Golaszewski , Rob Herring , Jean Delvare , Guenter Roeck , Lee Jones , Thierry Reding , =?utf-8?q?Uwe_Kleine-K?= =?utf-8?b?w7ZuaWc=?= , Wim Van Sebroeck , Shawn Guo , Li Yang , Thomas Gleixner , Jason Cooper , Marc Zyngier , Mark Brown , Greg Kroah-Hartman , Andy Shevchenko , Catalin Marinas , Will Deacon , Pavel Machek , Michael Walle Subject: [PATCH v8 06/13] pwm: add support for sl28cpld PWM controller Date: Thu, 13 Aug 2020 14:48:25 +0200 Message-Id: <20200813124832.17349-7-michael@walle.cc> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200813124832.17349-1-michael@walle.cc> References: <20200813124832.17349-1-michael@walle.cc> MIME-Version: 1.0 X-Spam: Yes Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org Add support for the PWM controller of the sl28cpld board management controller. This is part of a multi-function device driver. The controller has one PWM channel and can just generate four distinct frequencies. Signed-off-by: Michael Walle Acked-by: Thierry Reding --- Changes since v7: - added "depends on MFD_SL28CPLD || COMPILE_TEST" - corrected comment about divison - sanitize pwm values before handing them over to the PWM core - check wether we need to write the the duty cycle first to avoid glitches Changes since v6: - added new row "period length" - fixed parenthesis mistake in the description of a calculation - added sl28cpld_pwm_{read/write}() - added more error messages Changes since v5: - added brief description of the PWM hardware implementation - added hardware limitations - dropped the frequency mode table, instead calculate the prescaler value on the fly. - round the requested parameters instead of support just distinct periods. - prefix the macros by SL28CPLD_ to make them less generic - set polarity to PWM_POLARITY_NORMAL and reject inverted polarity requests. - apply the workaround just for prescaler value of 0. - make errors during probing more verbose Changes since v4: - update copyright year - remove #include , suggested by Andy. - make the pwm mode table look nicer, suggested by Lee. - use dev_get_drvdata(chip->dev) instead of container_of(), suggested by Lee. - use whole sentence in comments, suggested by Lee. - renamed the local "struct sl28cpld_pwm" variable to "priv" everywhere, suggested by Lee. - use pwm_{get,set}_relative_duty_cycle(), suggested by Andy. - make the comment about the 250Hz hardware limitation clearer - don't use "if (ret < 0)", but only "if (ret)", suggested by Andy. - don't use KBUID_MODNAME - remove comma in terminator line of the compatible strings list - remove the platform device table Changes since v3: - see cover letter drivers/pwm/Kconfig | 10 ++ drivers/pwm/Makefile | 1 + drivers/pwm/pwm-sl28cpld.c | 269 +++++++++++++++++++++++++++++++++++++ 3 files changed, 280 insertions(+) create mode 100644 drivers/pwm/pwm-sl28cpld.c diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 7dbcf6973d33..3dd9c23997e7 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -428,6 +428,16 @@ config PWM_SIFIVE To compile this driver as a module, choose M here: the module will be called pwm-sifive. +config PWM_SL28CPLD + tristate "Kontron sl28cpld PWM support" + depends on MFD_SL28CPLD || COMPILE_TEST + help + Generic PWM framework driver for board management controller + found on the Kontron sl28 CPLD. + + To compile this driver as a module, choose M here: the module + will be called pwm-sl28cpld. + config PWM_SPEAR tristate "STMicroelectronics SPEAr PWM support" depends on PLAT_SPEAR || COMPILE_TEST diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 2c2ba0a03557..cbdcd55d69ee 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -40,6 +40,7 @@ obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o obj-$(CONFIG_PWM_SAMSUNG) += pwm-samsung.o obj-$(CONFIG_PWM_SIFIVE) += pwm-sifive.o +obj-$(CONFIG_PWM_SL28CPLD) += pwm-sl28cpld.o obj-$(CONFIG_PWM_SPEAR) += pwm-spear.o obj-$(CONFIG_PWM_SPRD) += pwm-sprd.o obj-$(CONFIG_PWM_STI) += pwm-sti.o diff --git a/drivers/pwm/pwm-sl28cpld.c b/drivers/pwm/pwm-sl28cpld.c new file mode 100644 index 000000000000..29e338368d3e --- /dev/null +++ b/drivers/pwm/pwm-sl28cpld.c @@ -0,0 +1,269 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * sl28cpld PWM driver + * + * Copyright (c) 2020 Michael Walle + * + * There is no public datasheet available for this PWM core. But it is easy + * enough to be briefly explained. It consists of one 8-bit counter. The PWM + * supports four distinct frequencies by selecting when to reset the counter. + * With the prescaler setting you can select which bit of the counter is used + * to reset it. This implies that the higher the frequency the less remaining + * bits are available for the actual counter. + * + * Let cnt[7:0] be the counter, clocked at 32kHz: + * +-----------+--------+--------------+-----------+---------------+ + * | prescaler | reset | counter bits | frequency | period length | + * +-----------+--------+--------------+-----------+---------------+ + * | 0 | cnt[7] | cnt[6:0] | 250 Hz | 4000000 ns | + * | 1 | cnt[6] | cnt[5:0] | 500 Hz | 2000000 ns | + * | 2 | cnt[5] | cnt[4:0] | 1 kHz | 1000000 ns | + * | 3 | cnt[4] | cnt[3:0] | 2 kHz | 500000 ns | + * +-----------+--------+--------------+-----------+---------------+ + * + * Limitations: + * - The hardware cannot generate a 100% duty cycle if the prescaler is 0. + * - The hardware cannot atomically set the prescaler and the counter value, + * which might lead to glitches and inconsistent states if a write fails. + * - The counter is not reset if you switch the prescaler which leads + * to glitches, too. + * - The duty cycle will switch immediately and not after a complete cycle. + * - Depending on the actual implementation, disabling the PWM might have + * side effects. For example, if the output pin is shared with a GPIO pin + * it will automatically switch back to GPIO mode. + */ + +#include +#include +#include +#include +#include +#include +#include + +/* + * PWM timer block registers. + */ +#define SL28CPLD_PWM_CTRL 0x00 +#define SL28CPLD_PWM_CTRL_ENABLE BIT(7) +#define SL28CPLD_PWM_CTRL_PRESCALER_MASK GENMASK(1, 0) +#define SL28CPLD_PWM_CYCLE 0x01 +#define SL28CPLD_PWM_CYCLE_MAX GENMASK(6, 0) + +#define SL28CPLD_PWM_CLK 32000 /* 32 kHz */ +#define SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler) (1 << (7 - (prescaler))) +#define SL28CPLD_PWM_PERIOD(prescaler) \ + (NSEC_PER_SEC / SL28CPLD_PWM_CLK * SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler)) + +/* + * We calculate the duty cycle like this: + * duty_cycle_ns = pwm_cycle_reg * max_period_ns / max_duty_cycle + * + * With + * max_period_ns = 1 << (7 - prescaler) / pwm_clk * NSEC_PER_SEC + * max_duty_cycle = 1 << (7 - prescaler) + * this then simplifies to: + * duty_cycle_ns = pwm_cycle_reg / pwm_clk * NSEC_PER_SEC + * + * NSEC_PER_SEC is a multiple of SL28CPLD_PWM_CLK, therefore we're not losing + * precision by doing the divison first. + */ +#define SL28CPLD_PWM_TO_DUTY_CYCLE(reg) \ + (NSEC_PER_SEC / SL28CPLD_PWM_CLK * (reg)) +#define SL28CPLD_PWM_FROM_DUTY_CYCLE(duty_cycle) \ + (DIV_ROUND_DOWN_ULL((duty_cycle), NSEC_PER_SEC / SL28CPLD_PWM_CLK)) + +#define sl28cpld_pwm_read(priv, reg, val) \ + regmap_read((priv)->regmap, (priv)->offset + (reg), (val)) +#define sl28cpld_pwm_write(priv, reg, val) \ + regmap_write((priv)->regmap, (priv)->offset + (reg), (val)) + +struct sl28cpld_pwm { + struct pwm_chip pwm_chip; + struct regmap *regmap; + u32 offset; +}; + +static void sl28cpld_pwm_get_state(struct pwm_chip *chip, + struct pwm_device *pwm, + struct pwm_state *state) +{ + struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev); + unsigned int reg; + int prescaler; + + sl28cpld_pwm_read(priv, SL28CPLD_PWM_CTRL, ®); + + state->enabled = reg & SL28CPLD_PWM_CTRL_ENABLE; + + prescaler = FIELD_GET(SL28CPLD_PWM_CTRL_PRESCALER_MASK, reg); + state->period = SL28CPLD_PWM_PERIOD(prescaler); + + sl28cpld_pwm_read(priv, SL28CPLD_PWM_CYCLE, ®); + state->duty_cycle = SL28CPLD_PWM_TO_DUTY_CYCLE(reg); + state->polarity = PWM_POLARITY_NORMAL; + + /* + * Sanitize values for the PWM core. Depending on the prescaler it + * might happen that we calculate a duty_cycle greater than the actual + * period. This might happen if someone (e.g. the bootloader) sets an + * invalid combination of values. The behavior of the hardware is + * undefined in this case. But we need to report sane values back to + * the PWM core. + */ + state->duty_cycle = min(state->duty_cycle, state->period); +} + +static int sl28cpld_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev); + unsigned int cycle, prescaler; + bool write_duty_cycle_first; + int ret; + u8 ctrl; + + /* Polarity inversion is not supported */ + if (state->polarity != PWM_POLARITY_NORMAL) + return -EINVAL; + + /* + * Calculate the prescaler. Pick the biggest period that isn't + * bigger than the requested period. + */ + prescaler = DIV_ROUND_UP_ULL(SL28CPLD_PWM_PERIOD(0), state->period); + prescaler = order_base_2(prescaler); + + if (prescaler > field_max(SL28CPLD_PWM_CTRL_PRESCALER_MASK)) + return -ERANGE; + + ctrl = FIELD_PREP(SL28CPLD_PWM_CTRL_PRESCALER_MASK, prescaler); + if (state->enabled) + ctrl |= SL28CPLD_PWM_CTRL_ENABLE; + + cycle = SL28CPLD_PWM_FROM_DUTY_CYCLE(state->duty_cycle); + cycle = min_t(unsigned int, cycle, SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler)); + + /* + * Work around the hardware limitation. See also above. Trap 100% duty + * cycle if the prescaler is 0. Set prescaler to 1 instead. We don't + * care about the frequency because its "all-one" in either case. + * + * We don't need to check the actual prescaler setting, because only + * if the prescaler is 0 we can have this particular value. + */ + if (cycle == SL28CPLD_PWM_MAX_DUTY_CYCLE(0)) { + ctrl &= ~SL28CPLD_PWM_CTRL_PRESCALER_MASK; + ctrl |= FIELD_PREP(SL28CPLD_PWM_CTRL_PRESCALER_MASK, 1); + cycle = SL28CPLD_PWM_MAX_DUTY_CYCLE(1); + } + + /* + * To avoid glitches when we switch the prescaler, we have to make sure + * we have a valid duty cycle for the new mode. + * + * Take the current prescaler (or the current period length) into + * account to decide whether we have to write the duty cycle or the new + * prescaler first. If the period length is decreasing we have to + * write the duty cycle first. + */ + write_duty_cycle_first = pwm->state.period > state->period; + + if (write_duty_cycle_first) { + ret = sl28cpld_pwm_write(priv, SL28CPLD_PWM_CYCLE, cycle); + if (ret) + return ret; + } + + ret = sl28cpld_pwm_write(priv, SL28CPLD_PWM_CTRL, ctrl); + if (ret) + return ret; + + if (!write_duty_cycle_first) { + ret = sl28cpld_pwm_write(priv, SL28CPLD_PWM_CYCLE, cycle); + if (ret) + return ret; + } + + return 0; +} + +static const struct pwm_ops sl28cpld_pwm_ops = { + .apply = sl28cpld_pwm_apply, + .get_state = sl28cpld_pwm_get_state, + .owner = THIS_MODULE, +}; + +static int sl28cpld_pwm_probe(struct platform_device *pdev) +{ + struct sl28cpld_pwm *priv; + struct pwm_chip *chip; + int ret; + + if (!pdev->dev.parent) { + dev_err(&pdev->dev, "no parent device\n"); + return -ENODEV; + } + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->regmap = dev_get_regmap(pdev->dev.parent, NULL); + if (!priv->regmap) { + dev_err(&pdev->dev, "could not get parent regmap\n"); + return -ENODEV; + } + + ret = device_property_read_u32(&pdev->dev, "reg", &priv->offset); + if (ret) { + dev_err(&pdev->dev, "no 'reg' property found (%pe)\n", + ERR_PTR(ret)); + return -EINVAL; + } + + /* Initialize the pwm_chip structure */ + chip = &priv->pwm_chip; + chip->dev = &pdev->dev; + chip->ops = &sl28cpld_pwm_ops; + chip->base = -1; + chip->npwm = 1; + + ret = pwmchip_add(&priv->pwm_chip); + if (ret) { + dev_err(&pdev->dev, "failed to add PWM chip (%pe)", + ERR_PTR(ret)); + return ret; + } + + platform_set_drvdata(pdev, priv); + + return 0; +} + +static int sl28cpld_pwm_remove(struct platform_device *pdev) +{ + struct sl28cpld_pwm *priv = platform_get_drvdata(pdev); + + return pwmchip_remove(&priv->pwm_chip); +} + +static const struct of_device_id sl28cpld_pwm_of_match[] = { + { .compatible = "kontron,sl28cpld-pwm" }, + {} +}; +MODULE_DEVICE_TABLE(of, sl28cpld_pwm_of_match); + +static struct platform_driver sl28cpld_pwm_driver = { + .probe = sl28cpld_pwm_probe, + .remove = sl28cpld_pwm_remove, + .driver = { + .name = "sl28cpld-pwm", + .of_match_table = sl28cpld_pwm_of_match, + }, +}; +module_platform_driver(sl28cpld_pwm_driver); + +MODULE_DESCRIPTION("sl28cpld PWM Driver"); +MODULE_AUTHOR("Michael Walle "); +MODULE_LICENSE("GPL");