From: Fabrice Gasnier <fabrice.gasnier@st.com>
To: <jic23@kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <alexandre.torgue@st.com>,
<fabrice.gasnier@st.com>, <olivier.moysan@st.com>,
<linux-iio@vger.kernel.org>,
<linux-stm32@st-md-mailman.stormreply.com>
Subject: [PATCH] iio: adc: stm32-adc: adapt clock duty cycle for proper operation
Date: Fri, 6 Nov 2020 17:57:26 +0100 [thread overview]
Message-ID: <1604681846-31234-1-git-send-email-fabrice.gasnier@st.com> (raw)
For proper operation, STM32 ADC should be used with a clock duty cycle
of 50%, in the range of 49% to 51%. Depending on the clock tree, divider
can be used in case clock duty cycle is out of this range.
In case clk_get_scaled_duty_cycle() returns an error, kindly apply a
divider by default (don't make the probe fail).
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
drivers/iio/adc/stm32-adc-core.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
index cd870c0..d64a9e8 100644
--- a/drivers/iio/adc/stm32-adc-core.c
+++ b/drivers/iio/adc/stm32-adc-core.c
@@ -202,7 +202,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
{
u32 ckmode, presc, val;
unsigned long rate;
- int i, div;
+ int i, div, duty;
/* stm32h7 bus clock is common for all ADC instances (mandatory) */
if (!priv->bclk) {
@@ -226,6 +226,11 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
return -EINVAL;
}
+ /* If duty is an error, kindly use at least /2 divider */
+ duty = clk_get_scaled_duty_cycle(priv->aclk, 100);
+ if (duty < 0)
+ dev_warn(&pdev->dev, "adc clock duty: %d\n", duty);
+
for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;
presc = stm32h7_adc_ckmodes_spec[i].presc;
@@ -234,6 +239,13 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
if (ckmode)
continue;
+ /*
+ * For proper operation, clock duty cycle range is 49%
+ * to 51%. Apply at least /2 prescaler otherwise.
+ */
+ if (div == 1 && (duty < 49 || duty > 51))
+ continue;
+
if ((rate / div) <= priv->max_clk_rate)
goto out;
}
@@ -246,6 +258,10 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
return -EINVAL;
}
+ duty = clk_get_scaled_duty_cycle(priv->bclk, 100);
+ if (duty < 0)
+ dev_warn(&pdev->dev, "bus clock duty: %d\n", duty);
+
for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;
presc = stm32h7_adc_ckmodes_spec[i].presc;
@@ -254,6 +270,9 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
if (!ckmode)
continue;
+ if (div == 1 && (duty < 49 || duty > 51))
+ continue;
+
if ((rate / div) <= priv->max_clk_rate)
goto out;
}
--
2.7.4
next reply other threads:[~2020-11-06 16:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 16:57 Fabrice Gasnier [this message]
2020-11-08 15:18 ` [PATCH] iio: adc: stm32-adc: adapt clock duty cycle for proper operation Jonathan Cameron
2020-11-13 8:27 ` Fabrice Gasnier
2020-11-14 15:52 ` Jonathan Cameron
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=1604681846-31234-1-git-send-email-fabrice.gasnier@st.com \
--to=fabrice.gasnier@st.com \
--cc=alexandre.torgue@st.com \
--cc=jic23@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-stm32@st-md-mailman.stormreply.com \
--cc=olivier.moysan@st.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).