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clk: bcm2835: Skip PLLC clocks when deciding on a new clock parent 

If the firmware had set up a clock to source from PLLC, go along with
it.  But if we're looking for a new parent, we don't want to switch it
to PLLC because the firmware will force PLLC (and thus the AXI bus
clock) to different frequencies during over-temp/under-voltage,
without notification to Linux.

On my system, this moves the Linux-enabled HDMI state machine and DSI1
escape clock over to plld_per from pllc_per.  EMMC still ends up on
pllc_per, because the firmware had set it up to use that.

Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: 41691b8862 ("clk: bcm2835: Add support for programming the audio domain clocks")
Acked-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Eric Anholt 2016-06-01 12:05:36 -07:00 committed by Stephen Boyd
parent 9e400c5cc5
commit 67615c588a
1 changed files with 23 additions and 0 deletions
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23
drivers/clk/bcm/clk-bcm2835.c
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@ -1009,16 +1009,28 @@ static int bcm2835_clock_set_rate(struct clk_hw *hw,
return 0; return 0;
} }
static bool
bcm2835_clk_is_pllc(struct clk_hw *hw)
{
if (!hw)
return false;
return strncmp(clk_hw_get_name(hw), "pllc", 4) == 0;
}
static int bcm2835_clock_determine_rate(struct clk_hw *hw, static int bcm2835_clock_determine_rate(struct clk_hw *hw,
struct clk_rate_request *req) struct clk_rate_request *req)
{ {
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw); struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
struct clk_hw *parent, *best_parent = NULL; struct clk_hw *parent, *best_parent = NULL;
bool current_parent_is_pllc;
unsigned long rate, best_rate = 0; unsigned long rate, best_rate = 0;
unsigned long prate, best_prate = 0; unsigned long prate, best_prate = 0;
size_t i; size_t i;
u32 div; u32 div;
current_parent_is_pllc = bcm2835_clk_is_pllc(clk_hw_get_parent(hw));
/* /*
* Select parent clock that results in the closest but lower rate * Select parent clock that results in the closest but lower rate
*/ */
@ -1026,6 +1038,17 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
parent = clk_hw_get_parent_by_index(hw, i); parent = clk_hw_get_parent_by_index(hw, i);
if (!parent) if (!parent)
continue; continue;
/*
* Don't choose a PLLC-derived clock as our parent
* unless it had been manually set that way. PLLC's
* frequency gets adjusted by the firmware due to
* over-temp or under-voltage conditions, without
* prior notification to our clock consumer.
*/
if (bcm2835_clk_is_pllc(parent) && !current_parent_is_pllc)
continue;
prate = clk_hw_get_rate(parent); prate = clk_hw_get_rate(parent);
div = bcm2835_clock_choose_div(hw, req->rate, prate, true); div = bcm2835_clock_choose_div(hw, req->rate, prate, true);
rate = bcm2835_clock_rate_from_divisor(clock, prate, div); rate = bcm2835_clock_rate_from_divisor(clock, prate, div);