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Date: Tue, 10 Jul 2012 09:43:23 -0300
From: Alexandre Pereira da Silva <aletes.xgr@...il.com>
To: Thierry Reding <thierry.reding@...onic-design.de>
Cc: Roland Stigge <stigge@...com.de>,
Grant Likely <grant.likely@...retlab.ca>,
Rob Herring <rob.herring@...xeda.com>,
Rob Landley <rob@...dley.net>, linux-kernel@...r.kernel.org,
devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v2] pwm: add lpc32xx pwm support
On Tue, Jul 10, 2012 at 9:19 AM, Thierry Reding
<thierry.reding@...onic-design.de> wrote:
> On Tue, Jul 10, 2012 at 08:53:32AM -0300, Alexandre Pereira da Silva wrote:
>> Add lpc32xx soc pwm driver.
>
> The subject and this still need fixing (soc -> SOC, pwm -> PWM).
>
>> Signed-off-by: Alexandre Pereira da Silva <aletes.xgr@...il.com>
>> ---
>> Changes since v1:
>> * Style fixes
>> * Better error handling
>> * Improved Kconfig and DT descriptions
>>
>> .../devicetree/bindings/pwm/lpc32xx-pwm.txt | 17 +++
>> drivers/pwm/Kconfig | 11 ++
>> drivers/pwm/Makefile | 1 +
>> drivers/pwm/pwm-lpc32xx.c | 150 ++++++++++++++++++++
>> 4 files changed, 179 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
>> create mode 100644 drivers/pwm/pwm-lpc32xx.c
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
>> new file mode 100644
>> index 0000000..e7720e3
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
>> @@ -0,0 +1,17 @@
>> +LPC32XX PWM controller
>> +
>> +Required properties:
>> +- compatible: should be "nxp,lpc3220-pwm"
>> +- reg: physical base address and length of the controller's registers
>> +
>> +Examples:
>> +
>> +pwm1: pwm@...005C000 {
>> + compatible = "nxp,lpc3220-pwm";
>> + reg = <0x4005C000 0x4>;
>> +};
>> +
>> +pwm2: pwm@...005C004 {
>> + compatible = "nxp,lpc3220-pwm";
>> + reg = <0x4005C004 0x4>;
>> +};
>
> The PWM framework can support chips with multiple PWM devices. The
> LPC32xx seems to fit this model quite nicely, so you should instead
> instantiate one device and set npwm to 2.
>
>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>> index 0b2800f..ec2ac70 100644
>> --- a/drivers/pwm/Kconfig
>> +++ b/drivers/pwm/Kconfig
>> @@ -28,6 +28,17 @@ config PWM_IMX
>> To compile this driver as a module, choose M here: the module
>> will be called pwm-imx.
>>
>> +config PWM_LPC32XX
>> + tristate "LPC32XX PWM support"
>> + depends on ARCH_LPC32XX
>> + help
>> + Generic PWM framework driver for LPC32XX. The LPC32XX SOC has two
>> + PWM controllers.
>> +
>> + To compile this driver as a module, choose M here: the module
>> + will be called pwm-lpc32xx.
>> +
>> +
>
> There's a gratuitous blank line here, please remove.
>
>> config PWM_MXS
>> tristate "Freescale MXS PWM support"
>> depends on ARCH_MXS && OF
>> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
>> index cec2500..5459702 100644
>> --- a/drivers/pwm/Makefile
>> +++ b/drivers/pwm/Makefile
>> @@ -1,6 +1,7 @@
>> obj-$(CONFIG_PWM) += core.o
>> obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
>> obj-$(CONFIG_PWM_IMX) += pwm-imx.o
>> +obj-$(CONFIG_PWM_LPC32XX) += pwm-lpc32xx.o
>> obj-$(CONFIG_PWM_MXS) += pwm-mxs.o
>> obj-$(CONFIG_PWM_PXA) += pwm-pxa.o
>> obj-$(CONFIG_PWM_SAMSUNG) += pwm-samsung.o
>> diff --git a/drivers/pwm/pwm-lpc32xx.c b/drivers/pwm/pwm-lpc32xx.c
>> new file mode 100644
>> index 0000000..d79f4f9
>> --- /dev/null
>> +++ b/drivers/pwm/pwm-lpc32xx.c
>> @@ -0,0 +1,150 @@
>> +/*
>> + * Copyright 2012 Alexandre Pereira da Silva <aletes.xgr@...il.com>
>> + *
>> + * The code contained herein is licensed under the GNU General Public
>> + * License. You may obtain a copy of the GNU General Public License
>> + * Version 2 or later at the following locations:
>> + *
>> + * http://www.opensource.org/licenses/gpl-license.html
>> + * http://www.gnu.org/copyleft/gpl.html
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/err.h>
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pwm.h>
>> +#include <linux/slab.h>
>> +
>> +struct lpc32xx_pwm_chip {
>> + struct pwm_chip chip;
>> + struct clk *clk;
>> + void __iomem *base;
>> +};
>> +
>> +#define PWM_ENABLE (1 << 31)
>> +#define PWM_RELOADV(x) (((x) & 0xFF) << 8)
>> +#define PWM_DUTY(x) ((x) & 0xFF)
>> +
>> +#define to_lpc32xx_pwm_chip(_chip) \
>> + container_of(_chip, struct lpc32xx_pwm_chip, chip)
>> +
>> +static int lpc32xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>> + int duty_ns, int period_ns)
>> +{
>> + struct lpc32xx_pwm_chip *lpc32xx = to_lpc32xx_pwm_chip(chip);
>> + unsigned long long c;
>> + int period_cycles, duty_cycles;
>> +
>> + c = clk_get_rate(lpc32xx->clk) / 256;
>> + c = c * period_ns;
>> + do_div(c, NSEC_PER_SEC);
>> +
>> + /* Handle high and low extremes */
>> + if (c == 0)
>> + c = 1;
>> + if (c > 255)
>> + c = 0; /* 0 set division by 256 */
>> + period_cycles = c;
>> +
>> + c = 256 * duty_ns;
>> + do_div(c, period_ns);
>> + duty_cycles = c;
>> +
>> + writel(PWM_ENABLE | PWM_RELOADV(period_cycles) | PWM_DUTY(duty_cycles),
>> + lpc32xx->base);
>> +
>> + return 0;
>> +}
>
> When you convert to having more than one PWM device per chip, you can
> use pwm->hwpwm to distinguish between them. For this case this should be
> a trivial as:
>
> writel(..., lpc32xx->base + (pwm->hwpwm << 2));
I will try that. I didn't wrote the driver that way because of the clocks.
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