Messages in this thread | | | Date | Mon, 19 Sep 2022 23:30:41 +0100 | Subject | Re: [RFC v4 08/10] pwm: dwc: add of/platform support | From | Ben Dooks <> |
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On 14/09/2022 17:47, Uwe Kleine-König wrote: > On Tue, Aug 16, 2022 at 10:14:52PM +0100, Ben Dooks wrote: >> The dwc pwm controller can be used in non-PCI systems, so allow >> either platform or OF based probing. >> >> Signed-off-by: Ben Dooks <ben.dooks@sifive.com> >> --- >> v4: >> - split the of code out of the core >> - moved the compile test code earlier >> - fixed review comments >> - used NS_PER_SEC >> - use devm_clk_get_enabled >> v3: >> - changed compatible name >> --- >> drivers/pwm/Kconfig | 9 +++++ >> drivers/pwm/Makefile | 1 + >> drivers/pwm/pwm-dwc-of.c | 78 ++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 88 insertions(+) >> create mode 100644 drivers/pwm/pwm-dwc-of.c >> >> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig >> index a9f1c554db2b..f1735653365f 100644 >> --- a/drivers/pwm/Kconfig >> +++ b/drivers/pwm/Kconfig >> @@ -192,6 +192,15 @@ config PWM_DWC_PCI >> To compile this driver as a module, choose M here: the module >> will be called pwm-dwc-pci. >> >> +config PWM_DWC_OF >> + tristate "DesignWare PWM Controller (OF bus) >> + depends on PWM_DWC && OF >> + help >> + PWM driver for Synopsys DWC PWM Controller on an OF bus. >> + >> + To compile this driver as a module, choose M here: the module >> + will be called pwm-dwc-of. >> + >> config PWM_EP93XX >> tristate "Cirrus Logic EP93xx PWM support" >> depends on ARCH_EP93XX || COMPILE_TEST >> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile >> index a70d36623129..d1fd1641f077 100644 >> --- a/drivers/pwm/Makefile >> +++ b/drivers/pwm/Makefile >> @@ -15,6 +15,7 @@ obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o >> obj-$(CONFIG_PWM_CRC) += pwm-crc.o >> obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o >> obj-$(CONFIG_PWM_DWC) += pwm-dwc.o >> +obj-$(CONFIG_PWM_DWC_OF) += pwm-dwc-of.o >> obj-$(CONFIG_PWM_DWC_PCI) += pwm-dwc-pci.o >> obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o >> obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o >> diff --git a/drivers/pwm/pwm-dwc-of.c b/drivers/pwm/pwm-dwc-of.c >> new file mode 100644 >> index 000000000000..d18fac287325 >> --- /dev/null >> +++ b/drivers/pwm/pwm-dwc-of.c >> @@ -0,0 +1,78 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * DesignWare PWM Controller driver OF >> + * >> + * Copyright (C) 2022 SiFive, Inc. >> + */ >> + >> +#include <linux/bitops.h> >> +#include <linux/export.h> >> +#include <linux/kernel.h> >> +#include <linux/module.h> >> +#include <linux/clk.h> >> +#include <linux/platform_device.h> >> +#include <linux/pm_runtime.h> >> +#include <linux/pwm.h> >> +#include <linux/io.h> >> + >> +#include "pwm-dwc.h" >> + >> +static int dwc_pwm_plat_probe(struct platform_device *pdev) >> +{ >> + struct device *dev = &pdev->dev; >> + struct dwc_pwm *dwc; >> + int ret; >> + >> + dwc = dwc_pwm_alloc(dev); >> + if (!dwc) >> + return -ENOMEM; >> + >> + dwc->base = devm_platform_ioremap_resource(pdev, 0); >> + if (IS_ERR(dwc->base)) >> + return dev_err_probe(dev, PTR_ERR(dwc->base), >> + "failed to map IO\n"); > > devm_platform_ioremap_resource() already emits an error message.
ok, fixed
>> + >> + dwc->clk = devm_clk_get_enabled(dev, "timer"); >> + if (IS_ERR(dwc->clk)) >> + return dev_err_probe(dev, PTR_ERR(dwc->clk), >> + "failed to get timer clock\n"); >> + >> + clk_prepare_enable(dwc->clk); > > You don't need clk_prepare_enable() as you used devm_clk_get_enabled(). > > (Otherwise, when keeping clk_prepare_enable() you need to check the > return value.)
ok, fixed. I didn't notice that when changing to devm_
> >> + dwc->clk_ns = NSEC_PER_SEC / clk_get_rate(dwc->clk); > > I think I already pointed out this is non-optimal. > > Later you use clk_ns in __dwc_pwm_configure_timer(): > > tmp = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, dwc->clk_ns); > > So what you really want here is: > > tmp = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * clk_get_rate(dwc->clk), NSEC_PER_SEC); > > With for example clk_get_rate(dwc->clk) = 201171875 and duty_cycle = > 4096 you now get clk_ns = 4 (while the exact value is 4.97087..), tmp = > 1024, while the exact value is 824. > > So the idea is to add a clkrate member to the private driver struct, let > it default to 100000000 for the pci case and use the line I suggested > above.
ok, will consider keeping the rate in hz and modifiying the pci version to use 10 * NSEC_PER_SEC for the rate.
I've been trying to avoid changing the pci case, but I think for anything with a clk pointer we should be doing clk_get_rate in the calc code
> >> + >> + ret = devm_pwmchip_add(dev, &dwc->chip); >> + if (ret) >> + return ret; >> + >> + return 0; > > This is equivalent to > > return ret;
Will sort that out.
>> +} >> + >> +static int dwc_pwm_plat_remove(struct platform_device *pdev) >> +{ >> + struct dwc_pwm *dwc = platform_get_drvdata(pdev); >> + >> + clk_disable_unprepare(dwc->clk); >> + return 0; >> +} > > When dropping clk_prepare_enable() the .remove callback can go away, > too.
thanks, spotted that one a while ago.
>> + >> +static const struct of_device_id dwc_pwm_dt_ids[] = { >> + { .compatible = "snps,dw-apb-timers-pwm2" }, >> + { }, >> +}; >> +MODULE_DEVICE_TABLE(of, dwc_pwm_dt_ids); >> + >> +static struct platform_driver dwc_pwm_plat_driver = { >> + .driver = { >> + .name = "dwc-pwm", >> + .of_match_table = dwc_pwm_dt_ids, >> + }, >> + .probe = dwc_pwm_plat_probe, >> + .remove = dwc_pwm_plat_remove, >> +}; >> + >> +module_platform_driver(dwc_pwm_plat_driver); >> + >> +MODULE_ALIAS("platform:dwc-pwm-of"); >> +MODULE_AUTHOR("Ben Dooks <ben.dooks@sifive.com>"); >> +MODULE_DESCRIPTION("DesignWare PWM Controller"); >> +MODULE_LICENSE("GPL"); > > Best regards > Uwe >
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