| Message ID | 20210702095922.118614-2-s.riedmueller@phytec.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: mt9p031: Read back the real clock rate | expand |
Hi Enrico, On Fri, Jul 02, 2021 at 11:59:17AM +0200, Stefan Riedmueller wrote: > From: Enrico Scholz <enrico.scholz@sigma-chemnitz.de> > > The real and requested clock can differ and because it is used to > calculate PLL values, the real clock rate should be read. Do you have a system where this happens? That suggests there's a wrong value in DT. The preference nowadays is to rely on assigned-clock-rates, even though it's inherently somewhat unreliable, just as clk_set_rate(). This is an existing driver though. The old ones could be kept for compatibility with older DT binaries. > > Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de> > Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > drivers/media/i2c/mt9p031.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c > index 77567341ec98..3eaaa8d44523 100644 > --- a/drivers/media/i2c/mt9p031.c > +++ b/drivers/media/i2c/mt9p031.c > @@ -255,6 +255,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) > > struct i2c_client *client = v4l2_get_subdevdata(&mt9p031->subdev); > struct mt9p031_platform_data *pdata = mt9p031->pdata; > + unsigned long ext_freq; > int ret; > > mt9p031->clk = devm_clk_get(&client->dev, NULL); > @@ -265,13 +266,15 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) > if (ret < 0) > return ret; > > + ext_freq = clk_get_rate(mt9p031->clk); > + > /* If the external clock frequency is out of bounds for the PLL use the > * pixel clock divider only and disable the PLL. > */ > - if (pdata->ext_freq > limits.ext_clock_max) { > + if (ext_freq > limits.ext_clock_max) { > unsigned int div; > > - div = DIV_ROUND_UP(pdata->ext_freq, pdata->target_freq); > + div = DIV_ROUND_UP(ext_freq, pdata->target_freq); > div = roundup_pow_of_two(div) / 2; > > mt9p031->clk_div = min_t(unsigned int, div, 64); > @@ -280,7 +283,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) > return 0; > } > > - mt9p031->pll.ext_clock = pdata->ext_freq; > + mt9p031->pll.ext_clock = ext_freq; > mt9p031->pll.pix_clock = pdata->target_freq; > mt9p031->use_pll = true; >
Hi Sakari, On Mon, 2021-07-05 at 10:13 +0300, Sakari Ailus wrote: > Hi Enrico, > > On Fri, Jul 02, 2021 at 11:59:17AM +0200, Stefan Riedmueller wrote: > > From: Enrico Scholz <enrico.scholz@sigma-chemnitz.de> > > > > The real and requested clock can differ and because it is used to > > calculate PLL values, the real clock rate should be read. > > Do you have a system where this happens? That suggests there's a wrong > value in DT. The use case here is when the clock is supplied by one of the clock outputs of a SOC which might not hit the requested frequency exactly due to internal PLL configuration. So to get a better pixel clock the actual clock rate is read to calculate the PLL parameters on the sensor. At least that's the idea. Regards, Stefan > > The preference nowadays is to rely on assigned-clock-rates, even though > it's inherently somewhat unreliable, just as clk_set_rate(). This is an > existing driver though. The old ones could be kept for compatibility with > older DT binaries. > > > Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de> > > Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > --- > > drivers/media/i2c/mt9p031.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c > > index 77567341ec98..3eaaa8d44523 100644 > > --- a/drivers/media/i2c/mt9p031.c > > +++ b/drivers/media/i2c/mt9p031.c > > @@ -255,6 +255,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) > > > > struct i2c_client *client = v4l2_get_subdevdata(&mt9p031->subdev); > > struct mt9p031_platform_data *pdata = mt9p031->pdata; > > + unsigned long ext_freq; > > int ret; > > > > mt9p031->clk = devm_clk_get(&client->dev, NULL); > > @@ -265,13 +266,15 @@ static int mt9p031_clk_setup(struct mt9p031 > > *mt9p031) > > if (ret < 0) > > return ret; > > > > + ext_freq = clk_get_rate(mt9p031->clk); > > + > > /* If the external clock frequency is out of bounds for the PLL use > > the > > * pixel clock divider only and disable the PLL. > > */ > > - if (pdata->ext_freq > limits.ext_clock_max) { > > + if (ext_freq > limits.ext_clock_max) { > > unsigned int div; > > > > - div = DIV_ROUND_UP(pdata->ext_freq, pdata->target_freq); > > + div = DIV_ROUND_UP(ext_freq, pdata->target_freq); > > div = roundup_pow_of_two(div) / 2; > > > > mt9p031->clk_div = min_t(unsigned int, div, 64); > > @@ -280,7 +283,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) > > return 0; > > } > > > > - mt9p031->pll.ext_clock = pdata->ext_freq; > > + mt9p031->pll.ext_clock = ext_freq; > > mt9p031->pll.pix_clock = pdata->target_freq; > > mt9p031->use_pll = true; > >
diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c index 77567341ec98..3eaaa8d44523 100644 --- a/drivers/media/i2c/mt9p031.c +++ b/drivers/media/i2c/mt9p031.c @@ -255,6 +255,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) struct i2c_client *client = v4l2_get_subdevdata(&mt9p031->subdev); struct mt9p031_platform_data *pdata = mt9p031->pdata; + unsigned long ext_freq; int ret; mt9p031->clk = devm_clk_get(&client->dev, NULL); @@ -265,13 +266,15 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) if (ret < 0) return ret; + ext_freq = clk_get_rate(mt9p031->clk); + /* If the external clock frequency is out of bounds for the PLL use the * pixel clock divider only and disable the PLL. */ - if (pdata->ext_freq > limits.ext_clock_max) { + if (ext_freq > limits.ext_clock_max) { unsigned int div; - div = DIV_ROUND_UP(pdata->ext_freq, pdata->target_freq); + div = DIV_ROUND_UP(ext_freq, pdata->target_freq); div = roundup_pow_of_two(div) / 2; mt9p031->clk_div = min_t(unsigned int, div, 64); @@ -280,7 +283,7 @@ static int mt9p031_clk_setup(struct mt9p031 *mt9p031) return 0; } - mt9p031->pll.ext_clock = pdata->ext_freq; + mt9p031->pll.ext_clock = ext_freq; mt9p031->pll.pix_clock = pdata->target_freq; mt9p031->use_pll = true;