[v2,for-4.9,09/32] clk: bcm: Support rate change propagation on bcm2835 clocks

Message ID 1491388344-13521-10-git-send-email-amit.pundir@linaro.org
State New
Headers show
Series
  • Stable commits picked up from lede project
Related show

Commit Message

Amit Pundir April 5, 2017, 10:32 a.m.
From: Boris Brezillon <boris.brezillon@free-electrons.com>


Some peripheral clocks, like the VEC (Video EnCoder) clock need to be set
to a precise rate (in our case 108MHz). With the current implementation,
where peripheral clocks are not allowed to forward rate change requests
to their parents, it is impossible to match this requirement unless the
bootloader has configured things correctly, or a specific rate has been
assigned through the DT (with the assigned-clk-rates property).

Add a new field to struct bcm2835_clock_data to specify which parent
clocks accept rate change propagation, and support set rate propagation
in bcm2835_clock_determine_rate().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Reviewed-by: Eric Anholt <eric@anholt.net>

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

(cherry picked from commit 155e8b3b0ee320ae866b97dd31eba8a1f080a772)
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

---
 drivers/clk/bcm/clk-bcm2835.c | 67 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 63 insertions(+), 4 deletions(-)

-- 
2.7.4

Comments

Greg KH April 12, 2017, 1:17 p.m. | #1
On Wed, Apr 05, 2017 at 04:02:01PM +0530, Amit Pundir wrote:
> From: Boris Brezillon <boris.brezillon@free-electrons.com>

> 

> Some peripheral clocks, like the VEC (Video EnCoder) clock need to be set

> to a precise rate (in our case 108MHz). With the current implementation,

> where peripheral clocks are not allowed to forward rate change requests

> to their parents, it is impossible to match this requirement unless the

> bootloader has configured things correctly, or a specific rate has been

> assigned through the DT (with the assigned-clk-rates property).

> 

> Add a new field to struct bcm2835_clock_data to specify which parent

> clocks accept rate change propagation, and support set rate propagation

> in bcm2835_clock_determine_rate().

> 

> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> Reviewed-by: Eric Anholt <eric@anholt.net>

> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

> (cherry picked from commit 155e8b3b0ee320ae866b97dd31eba8a1f080a772)

> Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

> ---

>  drivers/clk/bcm/clk-bcm2835.c | 67 ++++++++++++++++++++++++++++++++++++++++---

>  1 file changed, 63 insertions(+), 4 deletions(-)


How does this match the stable kernel rules?

I'm confused.  Just because a distro/product includes patches in their
tree, does not mean they are all applicable for stable kernel releases.
Adding new device support in ways that is not just a simple quirk or
other table addition, isn't ok.

So this clk series isn't ok.  I'm going to drop this whole patch series
now.  Can you please review it, and resend any that you think are
applicable?

thanks,

greg k-h
Amit Pundir April 12, 2017, 1:33 p.m. | #2
On 12 April 2017 at 18:47, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Wed, Apr 05, 2017 at 04:02:01PM +0530, Amit Pundir wrote:

>> From: Boris Brezillon <boris.brezillon@free-electrons.com>

>>

>> Some peripheral clocks, like the VEC (Video EnCoder) clock need to be set

>> to a precise rate (in our case 108MHz). With the current implementation,

>> where peripheral clocks are not allowed to forward rate change requests

>> to their parents, it is impossible to match this requirement unless the

>> bootloader has configured things correctly, or a specific rate has been

>> assigned through the DT (with the assigned-clk-rates property).

>>

>> Add a new field to struct bcm2835_clock_data to specify which parent

>> clocks accept rate change propagation, and support set rate propagation

>> in bcm2835_clock_determine_rate().

>>

>> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

>> Reviewed-by: Eric Anholt <eric@anholt.net>

>> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

>> (cherry picked from commit 155e8b3b0ee320ae866b97dd31eba8a1f080a772)

>> Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

>> ---

>>  drivers/clk/bcm/clk-bcm2835.c | 67 ++++++++++++++++++++++++++++++++++++++++---

>>  1 file changed, 63 insertions(+), 4 deletions(-)

>

> How does this match the stable kernel rules?

>

> I'm confused.  Just because a distro/product includes patches in their

> tree, does not mean they are all applicable for stable kernel releases.

> Adding new device support in ways that is not just a simple quirk or

> other table addition, isn't ok.

>

> So this clk series isn't ok.  I'm going to drop this whole patch series

> now.  Can you please review it, and resend any that you think are

> applicable?


Ack. I'll review the series and resend the relevant patches.

Regards,
Amit Pundir

>

> thanks,

>

> greg k-h

Patch

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 2acaa77..df96fe6 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -436,6 +436,9 @@  struct bcm2835_clock_data {
 	const char *const *parents;
 	int num_mux_parents;
 
+	/* Bitmap encoding which parents accept rate change propagation. */
+	unsigned int set_rate_parent;
+
 	u32 ctl_reg;
 	u32 div_reg;
 
@@ -1017,10 +1020,60 @@  bcm2835_clk_is_pllc(struct clk_hw *hw)
 	return strncmp(clk_hw_get_name(hw), "pllc", 4) == 0;
 }
 
+static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+							int parent_idx,
+							unsigned long rate,
+							u32 *div,
+							unsigned long *prate)
+{
+	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+	struct bcm2835_cprman *cprman = clock->cprman;
+	const struct bcm2835_clock_data *data = clock->data;
+	unsigned long best_rate;
+	u32 curdiv, mindiv, maxdiv;
+	struct clk_hw *parent;
+
+	parent = clk_hw_get_parent_by_index(hw, parent_idx);
+
+	if (!(BIT(parent_idx) & data->set_rate_parent)) {
+		*prate = clk_hw_get_rate(parent);
+		*div = bcm2835_clock_choose_div(hw, rate, *prate, true);
+
+		return bcm2835_clock_rate_from_divisor(clock, *prate,
+						       *div);
+	}
+
+	if (data->frac_bits)
+		dev_warn(cprman->dev,
+			"frac bits are not used when propagating rate change");
+
+	/* clamp to min divider of 2 if we're dealing with a mash clock */
+	mindiv = data->is_mash_clock ? 2 : 1;
+	maxdiv = BIT(data->int_bits) - 1;
+
+	/* TODO: Be smart, and only test a subset of the available divisors. */
+	for (curdiv = mindiv; curdiv <= maxdiv; curdiv++) {
+		unsigned long tmp_rate;
+
+		tmp_rate = clk_hw_round_rate(parent, rate * curdiv);
+		tmp_rate /= curdiv;
+		if (curdiv == mindiv ||
+		    (tmp_rate > best_rate && tmp_rate <= rate))
+			best_rate = tmp_rate;
+
+		if (best_rate == rate)
+			break;
+	}
+
+	*div = curdiv << CM_DIV_FRAC_BITS;
+	*prate = curdiv * best_rate;
+
+	return best_rate;
+}
+
 static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 					struct clk_rate_request *req)
 {
-	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
 	struct clk_hw *parent, *best_parent = NULL;
 	bool current_parent_is_pllc;
 	unsigned long rate, best_rate = 0;
@@ -1048,9 +1101,8 @@  static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 		if (bcm2835_clk_is_pllc(parent) && !current_parent_is_pllc)
 			continue;
 
-		prate = clk_hw_get_rate(parent);
-		div = bcm2835_clock_choose_div(hw, req->rate, prate, true);
-		rate = bcm2835_clock_rate_from_divisor(clock, prate, div);
+		rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate,
+							  &div, &prate);
 		if (rate > best_rate && rate <= req->rate) {
 			best_parent = parent;
 			best_prate = prate;
@@ -1262,6 +1314,13 @@  static struct clk_hw *bcm2835_register_clock(struct bcm2835_cprman *cprman,
 	init.name = data->name;
 	init.flags = data->flags | CLK_IGNORE_UNUSED;
 
+	/*
+	 * Pass the CLK_SET_RATE_PARENT flag if we are allowed to propagate
+	 * rate changes on at least of the parents.
+	 */
+	if (data->set_rate_parent)
+		init.flags |= CLK_SET_RATE_PARENT;
+
 	if (data->is_vpu_clock) {
 		init.ops = &bcm2835_vpu_clock_clk_ops;
 	} else {