On 07/03/2015 07:52 AM, Sudeep Holla wrote:

Hi Stephen,


Thanks for the review.

On 02/07/15 18:23, Stephen Boyd wrote:

quoted

On 06/08, Sudeep Holla wrote:

quoted

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 9897f353bf1a..0fe8daefc105 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig

@@ -59,6 +59,16 @@ config COMMON_CLK_RK808
        clocked at 32KHz each. Clkout1 is always on, Clkout2 can off
        by control register.

+config COMMON_CLK_SCPI
+        tristate "Clock driver controlled via SCPI interface"
+        depends on ARM_SCPI_PROTOCOL || COMPILE_TEST
+        ---help---
+          This driver provides support for clocks that are controlled
+          by firmware that implements the SCPI interface.
+
+      This driver uses SCPI Message Protocol to interact with the
+      firmware providing all the clock controls.

The tabbing is weird here. Both paragraphs should have the same
alignment.

Indeed, sorry for that, fixed now.

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quoted

diff --git a/drivers/clk/clk-scpi.c b/drivers/clk/clk-scpi.c
new file mode 100644
index 000000000000..707b3430c55f
--- /dev/null
+++ b/drivers/clk/clk-scpi.c
+
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/scpi_protocol.h>

Please include <linux/platform_device.h> as well.

Added now, didn't bother as of_platform.h includes it.

quoted

quoted

+
+struct scpi_clk {
+    u32 id;
+    const char *name;

Do you need this? Or can you just use __clk_get_name() in places
where the name is used?

Not used, so removed it.


[...]

quoted

quoted

+static long scpi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
+                unsigned long *parent_rate)
+{

Maybe a comment here like:

/*
  * We can't figure out what rate it will be, so just return the rate
  * back to the caller. scpi_clk_recalc_rate() will be called
  * after the rate is set and we'll know what rate the clock is
  * running at then.
  */

Done

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+    return rate;
+}
+
+static int scpi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+                 unsigned long parent_rate)
+{
+    struct scpi_clk *clk = to_scpi_clk(hw);
+
+    return clk->scpi_ops->clk_set_val(clk->id, rate);
+}
+
+static void scpi_clk_disable(struct clk_hw *hw)
+{
+    scpi_clk_set_rate(hw, 0, 0);

Does this mean you have to set a rate to enable the clock? Are
you relying on drivers to call clk_set_rate() to implicitly
enable the clock? If so, it would be better to cache the rate of
the clock in set_rate if the clock isn't enabled in software and
then send the cached rate during enable.

Agreed, I have asked the firmware/SCPI specification guys about
more details on what to expect from firmware. Once they get back,
will update the code considering your feedback.

[...]

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+static int __scpi_find_dvfs_index(struct scpi_clk *clk, unsigned
long rate)
+{
+    int idx, max_opp = clk->info->count;
+    struct scpi_opp *opp = clk->info->opps;

const?

All the 3 above fixed now.

[...]

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+
+    clk = devm_clk_register(dev, &sclk->hw);
+    if (!IS_ERR(clk) && max)
+        clk_set_rate_range(clk, min, max);

Hm.. we're planning to make clk_register() return a struct
clk_hw, so this will block that. We need some sort of clk_hw API
that allows us to setup min/max limits on the clock from the
provider side. Care to add that?

Can you provide pointer to the patches or the tree containing those
changes ? Are they targeted for v4.3 ?

If I have time I may try to start doing the clk_register() conversion,
but it will take a while so I doubt it will be in v4.3. I'm asking if
you can add a clk_hw based API that does something like
clk_set_rate_range() without requiring a struct clk pointer. i.e.
clk_hw_set_rate_range(struct clk_hw *hw, min, max) that constraints the
min/max rate of the clock. This way, the driver is only using clk
provider APIs and not clk consumer APIs.

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