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

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

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.

quoted

Since clocks were enabling in set_power and clock rate can be set
during probe in single time instead of setting it in set_power for
every power enablement. anything wrong with that.

See above.

Plus, a clock running draws power. It doesn't really make sense to
draw power for something that is unused.

True, but clock is enabled only on sun6i_csi_set_power so setting
clock frequency in probe will draw power?
(sorry same message sent accidentally)

quoted

quoted

We discussed this in the previous iteration already.

What we didn't discuss is the variant function that you introduce,
while the previous approach was enough.

We discussed about clk_rate_exclusive_put, and that even handle it in
.remove right? so I have variant to handle it in sun6i_csi_remove.

We indeed discussed the clk_rate_exclusive_put. However, you chose to
implement it using a variant structure which really isn't needed.

Because clk_rate_exclusive_put will also do it .remove so adding
driver variant with mod_rate can do this job easily. do you have any
suggestion?