Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753897AbbFRKXt (ORCPT ); Thu, 18 Jun 2015 06:23:49 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:48557 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1753205AbbFRKXl (ORCPT ); Thu, 18 Jun 2015 06:23:41 -0400 X-Listener-Flag: 11101 Message-ID: <1434622784.18278.39.camel@mtksdaap41> Subject: Re: [PATCH v2 2/2] pwm: add MediaTek display PWM driver support From: YH Huang To: Thierry Reding CC: Matthias Brugger , Mark Rutland , Rob Herring , Pawel Moll , , , , , , , Sascha Hauer , , Date: Thu, 18 Jun 2015 18:19:44 +0800 In-Reply-To: <20150612102046.GF19400@ulmo.nvidia.com> References: <1432214964-40644-1-git-send-email-yh.huang@mediatek.com> <1432214964-40644-3-git-send-email-yh.huang@mediatek.com> <20150612102046.GF19400@ulmo.nvidia.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12293 Lines: 442 On Fri, 2015-06-12 at 12:20 +0200, Thierry Reding wrote: > On Thu, May 21, 2015 at 09:29:24PM +0800, YH Huang wrote: > > Add display PWM driver support to modify backlight for MT8173. > > > > Signed-off-by: YH Huang > > --- > > drivers/pwm/Kconfig | 10 ++ > > drivers/pwm/Makefile | 1 + > > drivers/pwm/pwm-mtk-disp.c | 228 +++++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 239 insertions(+) > > create mode 100644 drivers/pwm/pwm-mtk-disp.c > > > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > > index b1541f4..90e3c079 100644 > > --- a/drivers/pwm/Kconfig > > +++ b/drivers/pwm/Kconfig > > @@ -211,6 +211,16 @@ config PWM_LPSS_PLATFORM > > To compile this driver as a module, choose M here: the module > > will be called pwm-lpss-platform. > > > > +config PWM_MTK_DISP > > + tristate "MediaTek display PWM driver" > > + depends on HAS_IOMEM > > + help > > + Generic PWM framework driver for MediaTek disp-pwm device. > > + The PWM is used to control the backlight brightness for display. > > + > > + To compile this driver as a module, choose M here: the module > > + will be called pwm-mtk-disp. > > + > > config PWM_MXS > > tristate "Freescale MXS PWM support" > > depends on ARCH_MXS && OF > > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > > index ec50eb5..99c9e75 100644 > > --- a/drivers/pwm/Makefile > > +++ b/drivers/pwm/Makefile > > @@ -18,6 +18,7 @@ obj-$(CONFIG_PWM_LPC32XX) += pwm-lpc32xx.o > > obj-$(CONFIG_PWM_LPSS) += pwm-lpss.o > > obj-$(CONFIG_PWM_LPSS_PCI) += pwm-lpss-pci.o > > obj-$(CONFIG_PWM_LPSS_PLATFORM) += pwm-lpss-platform.o > > +obj-$(CONFIG_PWM_MTK_DISP) += pwm-mtk-disp.o > > obj-$(CONFIG_PWM_MXS) += pwm-mxs.o > > obj-$(CONFIG_PWM_PCA9685) += pwm-pca9685.o > > obj-$(CONFIG_PWM_PUV3) += pwm-puv3.o > > diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c > > new file mode 100644 > > index 0000000..d4e4cb6 > > --- /dev/null > > +++ b/drivers/pwm/pwm-mtk-disp.c > > @@ -0,0 +1,228 @@ > > +/* > > + * MediaTek display pulse-width-modulation controller driver. > > + * Copyright (c) 2015 MediaTek Inc. > > + * Author: YH Huang > > + * > > + * This program is free software; you can redistribute it and/or modify > > + * it under the terms of the GNU General Public License version 2 as > > + * published by the Free Software Foundation. > > + * > > + * This program is distributed in the hope that it will be useful, > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > + * GNU General Public License for more details. > > + */ > > + > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#define DISP_PWM_EN 0x0 > > +#define PWM_ENABLE_MASK 0x1 > > + > > +#define DISP_PWM_COMMIT 0x08 > > +#define PWM_COMMIT_MASK 0x1 > > + > > +#define DISP_PWM_CON_0 0x10 > > +#define PWM_CLKDIV_SHIFT 16 > > +#define PWM_CLKDIV_MASK (0x3ff << PWM_CLKDIV_SHIFT) > > +#define PWM_CLKDIV_MAX 0x000003ff > > I think you should make this: > > #define PWM_CLKDIV_MAX 0x3ff > #define PWM_CLKDIV_MASK (PWM_CLKDIV_MAX << PWM_CLKDIV_SHIFT) > > Just to show that these belong together. > It is much clear. > > + > > +#define DISP_PWM_CON_1 0x14 > > +#define PWM_PERIOD_MASK 0xfff > > +#define PWM_PERIOD_MAX 0x00000fff > > Same here. PWM_PERIOD_MAX isn't actually used anywhere, so perhaps just > drop it altogether. But see also below... > > > +/* Shift log2(PWM_PERIOD_MAX + 1) as divisor */ > > +#define PWM_PERIOD_BIT_SHIFT 12 > > I wasn't very clear about this in my earlier review, so let me try to > explain why I think this is confusing. You use this as a divisor, but > you encode it as a shift. It's also PWM_PERIOD_MAX + 1, so I think it > would make more sense to drop this, keep PWM_PERIOD_MAX as above and > then replace the > > >> PWM_PERIOD_BIT_SHIFT > > below by > > / (PWM_PERIOD_MAX + 1) > Maybe I can change in this way: Remove this: #define PWM_PERIOD_MAX 0x00000fff Using ">> PWM_PERIOD_BIT_SHIFT" is faster than "/ (PWM_PERIOD_MAX + 1)" Is this right? > > +#define PWM_HIGH_WIDTH_SHIFT 16 > > +#define PWM_HIGH_WIDTH_MASK (0x1fff << PWM_HIGH_WIDTH_SHIFT) > > Why is the mask wider than for the period? That would imply that the > duty cycle can be longer than a period, which doesn't make any sense. > Can you clarify? > After discussing with the hardware designer, the duty cycle is calculated by "high_width / (period + 1)". If period is the "magic number 0xfff", high_width needs 13 bits to show the situation that duty cycle is 100%. I should fix the formula for high_width below. > > +struct mtk_disp_pwm { > > + struct pwm_chip chip; > > + struct device *dev; > > + struct clk *clk_main; > > + struct clk *clk_mm; > > + void __iomem *mmio_base; > > I think "base" will do just fine. > OK. > > +}; > > + > > +static inline struct mtk_disp_pwm *to_mtk_disp_pwm(struct pwm_chip *chip) > > +{ > > + return container_of(chip, struct mtk_disp_pwm, chip); > > +} > > + > > +static void mtk_disp_pwm_update_bits(void __iomem *address, u32 mask, u32 value) > > +{ > > + u32 val; > > + > > + val = readl(address); > > + val &= ~mask; > > + val |= value; > > + writel(val, address); > > +} > > + > > +static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > + int duty_ns, int period_ns) > > +{ > > + struct mtk_disp_pwm *mdp; > > + u64 div, rate; > > + u32 clk_div, period, high_width, value; > > + > > + /* > > + * Find period, high_width and clk_div to suit duty_ns and period_ns. > > + * Calculate proper div value to keep period value in the bound. > > + * > > + * period_ns = 10^9 * (clk_div + 1) * (period +1) / PWM_CLK_RATE > > Nit: should have a space between '+' and '1'. > OK. > > + * duty_ns = 10^9 * (clk_div + 1) * (high_width + 1) / PWM_CLK_RATE Here should be duty_ns = 10^9 * (clk_div + 1) * high_width / PWM_CLK_RATE > > + * > > + * period = (PWM_CLK_RATE * period_ns) / (10^9 * (clk_div + 1)) - 1 > > + * high_width = (PWM_CLK_RATE * duty_ns) / (10^9 * (clk_div + 1)) - 1 And here high_width = (PWM_CLK_RATE * duty_ns) / (10^9 * (clk_div + 1)) > > + */ > > + mdp = to_mtk_disp_pwm(chip); > > Please put this on the same line as the variable declaration: > > struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip); > OK. > > + rate = clk_get_rate(mdp->clk_main); > > + clk_div = div_u64(rate * period_ns, NSEC_PER_SEC) >> > > + PWM_PERIOD_BIT_SHIFT; > > + if (clk_div > PWM_CLKDIV_MAX) > > + return -EINVAL; > > + > > + div = clk_div + 1; > > Perhaps make this: > > div = NSEC_PER_SEC * (clk_div + 1); > > to avoid the two multiplication below. > You are right. > > + period = div64_u64(rate * period_ns, NSEC_PER_SEC * div); > > So this would become: > > period = div64_u64(rate * period_ns, div); > Got it. > > + if (period > 0) > > + period--; > > + > > + high_width = div64_u64(rate * duty_ns, NSEC_PER_SEC * div); > > And this: > > high_width = div64_u64(rate * duty_ns, div); > OK. > > + if (high_width > 0) > > + high_width--; I should remove this two lines above for the new formula. > > + > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_CON_0, > > + PWM_CLKDIV_MASK, clk_div << PWM_CLKDIV_SHIFT); > > + > > + value = period | (high_width << PWM_HIGH_WIDTH_SHIFT); > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_CON_1, > > + PWM_PERIOD_MASK | PWM_HIGH_WIDTH_MASK, value); > > + > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_COMMIT, > > + PWM_COMMIT_MASK, 1); > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_COMMIT, > > + PWM_COMMIT_MASK, 0); > > + > > + return 0; > > +} > > + > > +static int mtk_disp_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) > > +{ > > + struct mtk_disp_pwm *mdp; > > + > > + mdp = to_mtk_disp_pwm(chip); > > The above three lines should be collapsed. > OK. > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_EN, > > + PWM_ENABLE_MASK, 1); > > + > > + return 0; > > +} > > + > > +static void mtk_disp_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) > > +{ > > + struct mtk_disp_pwm *mdp; > > + > > + mdp = to_mtk_disp_pwm(chip); > > Same here. > OK. > > + mtk_disp_pwm_update_bits(mdp->mmio_base + DISP_PWM_EN, > > + PWM_ENABLE_MASK, 0); > > +} > > + > > +static const struct pwm_ops mtk_disp_pwm_ops = { > > + .config = mtk_disp_pwm_config, > > + .enable = mtk_disp_pwm_enable, > > + .disable = mtk_disp_pwm_disable, > > + .owner = THIS_MODULE, > > +}; > > + > > +static int mtk_disp_pwm_probe(struct platform_device *pdev) > > +{ > > + struct mtk_disp_pwm *mdp; > > + struct resource *r; > > + int ret; > > + > > + mdp = devm_kzalloc(&pdev->dev, sizeof(*mdp), GFP_KERNEL); > > + if (!mdp) > > + return -ENOMEM; > > + > > + mdp->dev = &pdev->dev; > > + > > + r = platform_get_resource(pdev, IORESOURCE_MEM, 0); > > + mdp->mmio_base = devm_ioremap_resource(&pdev->dev, r); > > + if (IS_ERR(mdp->mmio_base)) > > + return PTR_ERR(mdp->mmio_base); > > + > > + mdp->clk_main = devm_clk_get(&pdev->dev, "main"); > > + if (IS_ERR(mdp->clk_main)) > > + return PTR_ERR(mdp->clk_main); > > + > > + mdp->clk_mm = devm_clk_get(&pdev->dev, "mm"); > > + if (IS_ERR(mdp->clk_mm)) > > + return PTR_ERR(mdp->clk_mm); > > + > > + ret = clk_prepare_enable(mdp->clk_main); > > + if (ret < 0) > > + return ret; > > + > > + ret = clk_prepare_enable(mdp->clk_mm); > > + if (ret < 0) { > > + clk_disable_unprepare(mdp->clk_main); > > + return ret; > > + } > > + > > + platform_set_drvdata(pdev, mdp); > > + > > + mdp->chip.dev = &pdev->dev; > > + mdp->chip.ops = &mtk_disp_pwm_ops; > > + mdp->chip.base = -1; > > + mdp->chip.npwm = 1; > > + > > + ret = pwmchip_add(&mdp->chip); > > + if (ret < 0) { > > + dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret); > > + clk_disable_unprepare(mdp->clk_main); > > + clk_disable_unprepare(mdp->clk_mm); > > + return ret; > > + } > > + > > + return 0; > > +} > > It's customary to collect the error cleanup code in an unwinding section > at the bottom of the function, like so: > > ret = clk_prepare_enable(mdp->clk_mm); > if (ret < 0) > goto disable_clk_main; > > ... > > ret = pwmchip_add(&mdp->chip); > if (ret < 0) { > dev_err(&pdev->dev, ...); > goto disable_clk_mm; > } > > return 0; > > disable_clk_mm: > clk_disable_unprepare(mdp->clk_mm); > disable_clk_main: > clk_disable_unprepare(mdp->clk_main); > return ret; > > This makes sure that you undo things in the proper order and eliminates > the need to duplicate cleanup code in all failure paths. > I will rewrite this part. > > + > > +static int mtk_disp_pwm_remove(struct platform_device *pdev) > > +{ > > + struct mtk_disp_pwm *mdp; > > + int ret; > > + > > + mdp = platform_get_drvdata(pdev); > > Should be on the same line as the variable declaration. > OK. > > + ret = pwmchip_remove(&mdp->chip); > > + clk_disable_unprepare(mdp->clk_main); > > + clk_disable_unprepare(mdp->clk_mm); > > + > > + return ret; > > +} > > + > > +static const struct of_device_id mtk_disp_pwm_of_match[] = { > > + { .compatible = "mediatek,mt8173-disp-pwm" }, > > + { .compatible = "mediatek,mt6595-disp-pwm" }, > > + { } > > +}; > > +MODULE_DEVICE_TABLE(of, mtk_disp_pwm_of_match); > > + > > +static struct platform_driver mtk_disp_pwm_driver = { > > + .driver = { > > + .name = "mediatek-disp-pwm", > > + .of_match_table = mtk_disp_pwm_of_match, > > + }, > > + .probe = mtk_disp_pwm_probe, > > + .remove = mtk_disp_pwm_remove, > > +}; > > +module_platform_driver(mtk_disp_pwm_driver); > > + > > +MODULE_AUTHOR("YH Huang "); > > +MODULE_DESCRIPTION("MediaTek SoC display PWM driver"); > > +MODULE_LICENSE("GPL v2"); > > Thierry Thank for your suggestion. Regards, YH Huang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/