From: Sean Cross <xobs-nXMMniAx+RbQT0dZR+AlfA@public.gmane.org>
To: Thierry Reding
<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Grant Likely
<grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Sean Cross <xobs-nXMMniAx+RbQT0dZR+AlfA@public.gmane.org>
Subject: [PATCH] pwm: imx: Support very long period lengths
Date: Mon, 28 Apr 2014 16:55:31 +0800 [thread overview]
Message-ID: <1398675331-10980-2-git-send-email-xobs@kosagi.com> (raw)
In-Reply-To: <1398675331-10980-1-git-send-email-xobs-nXMMniAx+RbQT0dZR+AlfA@public.gmane.org>
The IMX PWM block supports using both the system clock and a 32 kHz
clock for driving PWM events. For very long period lengths, use the
32 kHz clock instead of the high-speed clock.
Signed-off-by: Sean Cross <xobs-nXMMniAx+RbQT0dZR+AlfA@public.gmane.org>
---
drivers/pwm/pwm-imx.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
index cc47733..8410455 100644
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -36,9 +36,11 @@
#define MX3_PWMCR_DOZEEN (1 << 24)
#define MX3_PWMCR_WAITEN (1 << 23)
#define MX3_PWMCR_DBGEN (1 << 22)
+#define MX3_PWMCR_CLKSRC_IPG_32K (3 << 16)
#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
#define MX3_PWMCR_CLKSRC_IPG (1 << 16)
#define MX3_PWMCR_EN (1 << 0)
+#define MX3_SLOW_THRESHOLD_NS 100000
struct imx_chip {
struct clk *clk_per;
@@ -107,7 +109,13 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
unsigned long period_cycles, duty_cycles, prescale;
u32 cr;
- c = clk_get_rate(imx->clk_per);
+ if (duty_ns > MX3_SLOW_THRESHOLD_NS) {
+ cr = MX3_PWMCR_CLKSRC_IPG_32K;
+ c = 32768;
+ } else {
+ cr = MX3_PWMCR_CLKSRC_IPG_HIGH;
+ c = clk_get_rate(imx->clk_per);
+ }
c = c * period_ns;
do_div(c, 1000000000);
period_cycles = c;
@@ -131,9 +139,9 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
writel(period_cycles, imx->mmio_base + MX3_PWMPR);
- cr = MX3_PWMCR_PRESCALER(prescale) |
+ cr |= MX3_PWMCR_PRESCALER(prescale) |
MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
- MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH;
+ MX3_PWMCR_DBGEN;
if (test_bit(PWMF_ENABLED, &pwm->flags))
cr |= MX3_PWMCR_EN;
--
1.9.2
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2014-04-28 8:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-28 8:55 [PATCH] pwm: imx: Add support for low-speed PWM Sean Cross
[not found] ` <1398675331-10980-1-git-send-email-xobs-nXMMniAx+RbQT0dZR+AlfA@public.gmane.org>
2014-04-28 8:55 ` Sean Cross [this message]
2014-04-28 9:22 ` [PATCH] pwm: imx: Support very long period lengths Sascha Hauer
2014-04-28 12:10 ` Sean Cross
2014-04-28 12:43 ` Sascha Hauer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1398675331-10980-2-git-send-email-xobs@kosagi.com \
--to=xobs-nxmmniax+rbqt0dzr+alfa@public.gmane.org \
--cc=devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org \
--cc=linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org \
--cc=thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.