linux-kernel - Re: [RFC v4 06/10] pwm: dwc: split pci out of core driver

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Date:   Fri, 19 Aug 2022 17:56:10 +0100
From:   Ben Dooks <ben.dooks@...ive.com>
To:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        linux-pwm@...r.kernel.org
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>,
        u.kleine-koenig@...gutronix.de,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        William Salmon <william.salmon@...ive.com>,
        Jude Onyenegecha <jude.onyenegecha@...ive.com>
Subject: Re: [RFC v4 06/10] pwm: dwc: split pci out of core driver

On 19/08/2022 14:38, Jarkko Nikula wrote:
> Hi
> 
> On 8/17/22 00:14, Ben Dooks wrote:
>> Moving towards adding non-pci support for the driver, move the pci
>> parts out of the core into their own module. This is partly due to
>> the module_driver() code only being allowed once in a module and also
>> to avoid a number of #ifdef if we build a single file in a system
>> without pci support.
>>
>> Signed-off-by: Ben Dooks <ben.dooks@...ive.com>
>> ---
> 
> I quickly tested this on Intel Elkhart and didn't notice any regression. 
> A few comments below.
> 
>>   drivers/pwm/Kconfig       |  14 +++-
>>   drivers/pwm/Makefile      |   1 +
>>   drivers/pwm/pwm-dwc-pci.c | 133 ++++++++++++++++++++++++++++++++
>>   drivers/pwm/pwm-dwc.c     | 158 +-------------------------------------
>>   drivers/pwm/pwm-dwc.h     |  58 ++++++++++++++
>>   5 files changed, 207 insertions(+), 157 deletions(-)
>>   create mode 100644 drivers/pwm/pwm-dwc-pci.c
>>   create mode 100644 drivers/pwm/pwm-dwc.h
>>
>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>> index 3f3c53af4a56..a9f1c554db2b 100644
>> --- a/drivers/pwm/Kconfig
>> +++ b/drivers/pwm/Kconfig
>> @@ -175,15 +175,23 @@ config PWM_CROS_EC
>>         Controller.
>>   config PWM_DWC
>> -    tristate "DesignWare PWM Controller"
>> -    depends on PCI || COMPILE_TEST
>> +    tristate "DesignWare PWM Controller core"
>>       depends on HAS_IOMEM
>>       help
>> -      PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
>> +      PWM driver for Synopsys DWC PWM Controller.
>>         To compile this driver as a module, choose M here: the module
>>         will be called pwm-dwc.
>> +config PWM_DWC_PCI
>> +    tristate "DesignWare PWM Controller core"
> 
> Same text as core part has. How about "DesignWare PWM Controller PCI 
> driver"?

Thanks, did notice a couple of kconfig issues so will look at that.

> 
>> +    depends on PWM_DWC && HAS_IOMEM && PCI
>> +    help
>> +      PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
>> +
>> +      To compile this driver as a module, choose M here: the module
>> +      will be called pwm-dwc-pci.
>> +
>>   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 7bf1a29f02b8..a70d36623129 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-$(CONFIG_PWM_DWC_PCI)    += pwm-dwc-pci.o
>>   obj-$(CONFIG_PWM_EP93XX)    += pwm-ep93xx.o
>>   obj-$(CONFIG_PWM_FSL_FTM)    += pwm-fsl-ftm.o
>>   obj-$(CONFIG_PWM_HIBVT)        += pwm-hibvt.o
>> diff --git a/drivers/pwm/pwm-dwc-pci.c b/drivers/pwm/pwm-dwc-pci.c
>> new file mode 100644
>> index 000000000000..2213d0e7f3c8
>> --- /dev/null
>> +++ b/drivers/pwm/pwm-dwc-pci.c
>> @@ -0,0 +1,133 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * DesignWare PWM Controller driver (PCI part)
>> + *
>> + * Copyright (C) 2018-2020 Intel Corporation
>> + *
>> + * Author: Felipe Balbi (Intel)
>> + * Author: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
>> + * Author: Raymond Tan <raymond.tan@...el.com>
>> + *
>> + * Limitations:
>> + * - The hardware cannot generate a 0 % or 100 % duty cycle. Both 
>> high and low
>> + *   periods are one or more input clock periods long.
>> + */
>> +
> 
> I think this is more common limitation rather than PCI part.

The PCI is based off an core without the support, it is added
as a build option as of (IIRC) the 2.13 core.

> 
>> --- a/drivers/pwm/pwm-dwc.c
>> +++ b/drivers/pwm/pwm-dwc.c
>> @@ -1,16 +1,12 @@
>>   // SPDX-License-Identifier: GPL-2.0
>>   /*
>> - * DesignWare PWM Controller driver
>> + * DesignWare PWM Controller driver core
>>    *
>>    * Copyright (C) 2018-2020 Intel Corporation
>>    *
>>    * Author: Felipe Balbi (Intel)
>>    * Author: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
>>    * Author: Raymond Tan <raymond.tan@...el.com>
>> - *
>> - * Limitations:
>> - * - The hardware cannot generate a 0 % or 100 % duty cycle. Both 
>> high and low
>> - *   periods are one or more input clock periods long.
>>    */
> 
> Relates to previous comment, is there reason why this limitation is 
> removed from the core part?

See above.

> 
>> --- /dev/null
>> +++ b/drivers/pwm/pwm-dwc.h
>> +#define DWC_CLK_PERIOD_NS    10
> 
> Perhaps this addition can be removed if patch 7/10 goes before this 
> patch? It's anyway specific to PCI part only.

Will look into that