Re: [PATCH v5 2/6] media: sun6i: Add mod_rate quirk

On Fri, Jan 11, 2019 at 11:54:12AM +0530, Jagan Teki wrote:

On Mon, Jan 7, 2019 at 6:59 PM Maxime Ripard [off-list ref] wrote:

quoted

On Mon, Dec 24, 2018 at 08:57:48PM +0530, Jagan Teki wrote:

quoted

On Fri, Dec 21, 2018 at 6:30 PM Maxime Ripard [off-list ref] wrote:

quoted

On Thu, Dec 20, 2018 at 06:24:34PM +0530, Jagan Teki wrote:

quoted

Unfortunately default CSI_SCLK rate cannot work properly to
drive the connected sensor interface, particularly on few
Allwinner SoC's like A64.

So, add mod_rate quirk via driver data so-that the respective
SoC's which require to alter the default mod clock rate can assign
the operating clock rate.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
---
 .../platform/sunxi/sun6i-csi/sun6i_csi.c      | 34 +++++++++++++++----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
index ee882b66a5ea..fe002beae09c 100644
--- a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
+++ b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c

@@ -15,6 +15,7 @@
 #include <linux/ioctl.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>

@@ -28,8 +29,13 @@

 #define MODULE_NAME  "sun6i-csi"

+struct sun6i_csi_variant {
+     unsigned long                   mod_rate;
+};
+
 struct sun6i_csi_dev {
      struct sun6i_csi                csi;
+     const struct sun6i_csi_variant  *variant;
      struct device                   *dev;

      struct regmap                   *regmap;

@@ -822,33 +828,43 @@ static int sun6i_csi_resource_request(struct sun6i_csi_dev *sdev,
              return PTR_ERR(sdev->clk_mod);
      }

+     if (sdev->variant->mod_rate)
+             clk_set_rate_exclusive(sdev->clk_mod, sdev->variant->mod_rate);
+

It still doesn't make any sense to do it in the probe function...

I'm not sure we discussed about the context wrt probe, we discussed
about exclusive put clock.

https://lkml.org/lkml/2018/12/18/584

"Doing it here is not really optimal either, since you'll put a
constraint on the system (maintaining that clock at 300MHz), while
it's not in use."

But this constraint is only set, for SoC's who need mod_rate change
not for whole SoCs.

Still, that constraint is there for the whole system on affected
SoCs. Whether it applies to one SoC or not is not really relevant.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com