Re: [PATCH] hwmon: (aspeed-pwm-tacho) Use 24MHz clock

From: Guenter Roeck
Date: Tue May 08 2018 - 09:52:16 EST

On 05/08/2018 02:39 AM, Lei YU wrote:
The clock source for aspeed pwm is set to 24MHz, so use the hard-coded
clock frequency instead of the one in device tree.

Otherwise, in case of the clock specified in device tree is not 24MHz,
the fan speed will be incorrect.

Signed-off-by: Lei YU <mine260309@xxxxxxxxx>
drivers/hwmon/aspeed-pwm-tacho.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c
index 693a3d5..e83b8df 100644
--- a/drivers/hwmon/aspeed-pwm-tacho.c
+++ b/drivers/hwmon/aspeed-pwm-tacho.c
@@ -922,7 +922,6 @@ static int aspeed_pwm_tacho_probe(struct platform_device *pdev)
void __iomem *regs;
struct resource *res;
struct device *hwmon;
- struct clk *clk;
int ret;
np = dev->of_node;
@@ -956,12 +955,10 @@ static int aspeed_pwm_tacho_probe(struct platform_device *pdev)
regmap_write(priv->regmap, ASPEED_PTCR_TACH_SOURCE, 0);
regmap_write(priv->regmap, ASPEED_PTCR_TACH_SOURCE_EXT, 0);
- clk = devm_clk_get(dev, NULL);
- if (IS_ERR(clk))
- return -ENODEV;
- priv->clk_freq = clk_get_rate(clk);
aspeed_set_clock_enable(priv->regmap, true);
+ // The clock source is set to 24MHz

No mixed C/C++ comments in hwmon drivers.

aspeed_set_clock_source(priv->regmap, 0);
+ priv->clk_freq = 24000000;

Are you saying that clk_get_rate() is wrong ? Anyway, if the DT is bad, it should be fixed.
I am not a friend of hacking drivers to fix up bad DTs, and much less so without explanation.
Plus, how do we know that the next chip supported by the driver doesn't have a 32MHz clock ?
Really, please fix the DT.