Re: [PATCH 0/3] MIPS: JZ4740: Move PWM driver to PWM framework

Maarten ter Huurne
2012-09-02T13:44:15Z

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On Sunday 02 September 2012 11:52:27 Thierry Reding wrote:

> This small series fixes a build error due to a circular header
> dependency, exports the timer API so it can be used outside of
> the arch/mips/jz4740 tree and finally moves and converts the
> JZ4740 PWM driver to the PWM framework.
>
> Note that I don't have any hardware to test this on, so I had to
> rely on compile tests only. Patches 1 and 2 should probably go
> through the MIPS tree, while I can take patch 3 through the PWM
> tree. It touches a couple of files in arch/mips but the changes
> are unlikely to cause conflicts.

Exporting the hardware outputs PWM2-7 as index 0-5 in the PWM core is rather
confusing. I discussed with Lars on IRC and it's probably better to expose
PWM0-7 through the API, but refuse to hand out PWM0 and PWM1 when requested,
since their associated timers are in use by the system. I attached a diff
that illustrates this approach.

Note that if this approach is taken, the beeper ID in board-qi_lb60.c should
be changed back from 2 to 4, since the beeper is attached to PWM4.

I tested the "for-next" branch on the Dingoo A320 with the pwm-backlight
driver. It didn't work at first, because the PWM number and the timer number
didn't align: I requested PWM number 5 to get PWM7 and the GPIO of PWM7 was
used, but with timer 5 instead of timer 7, resulting in a dark screen.
However, it works fine after adding PWM0/1 as described above.

If other people want to test on real hardware, you can find the code in
branch jz-3.6-rc2-pwm in the qi-kernel repository. Unfortunately our web
interface for git is still broken, but the repo itself is fine.
git://projects.qi-hardware.com/qi-kernel.git

Bye,
Maarten

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diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
index db29b37..554e414 100644
--- a/drivers/pwm/pwm-jz4740.c
+++ b/drivers/pwm/pwm-jz4740.c
@@ -24,9 +24,11 @@
#include <asm/mach-jz4740/gpio.h>
#include <timer.h>

-#define NUM_PWM 6
+#define NUM_PWM 8

static const unsigned int jz4740_pwm_gpio_list[NUM_PWM] = {
+ JZ_GPIO_PWM0,
+ JZ_GPIO_PWM1,
JZ_GPIO_PWM2,
JZ_GPIO_PWM3,
JZ_GPIO_PWM4,
@@ -50,6 +52,13 @@ static int jz4740_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
unsigned int gpio = jz4740_pwm_gpio_list[pwm->hwpwm];
int ret;

+ /*
+ * Timer 0 and 1 are used for system tasks, so they are unavailable
+ * for use as PWMs.
+ */
+ if (pwm->hwpwm < 2)
+ return -EBUSY;
+
ret = gpio_request(gpio, pwm->label);

if (ret) {