* [PATCH v2 1/2] clk: vt8500: fix gcc-4.9 warnings
2016-06-07 21:56 [PATCH v2 0/2] Rework clk/vt8500 wm8650_find_pll_bits() Roman Volkov
@ 2016-06-07 21:56 ` Roman Volkov
2016-06-21 0:48 ` Stephen Boyd
2016-06-07 21:56 ` [PATCH v2 2/2] clk: vt8500: rework wm8650_find_pll_bits() Roman Volkov
1 sibling, 1 reply; 5+ messages in thread
From: Roman Volkov @ 2016-06-07 21:56 UTC (permalink / raw)
To: Stephen Boyd
Cc: Arnd Bergmann, linux-clk, linux-kernel, Michael Turquette,
Roman Volkov, Tony Prisk
From: Arnd Bergmann <arnd@arndb.de>
This fixes some false positive warnings we get with older compiler
versions:
clk-vt8500.c: In function ‘wm8650_find_pll_bits’:
clk-vt8500.c:430:12: ‘best_div2’ may be used uninitialized in this function
clk-vt8500.c:429:12: ‘best_div1’ may be used uninitialized in this function
clk-vt8500.c:428:14: ‘best_mul’ may be used uninitialized in this function
clk-vt8500.c: In function ‘wm8750_find_pll_bits’:
clk-vt8500.c:509:12: ‘best_div2’ may be used uninitialized in this function
clk-vt8500.c:508:12: ‘best_div1’ may be used uninitialized in this function
clk-vt8500.c:507:14: ‘best_mul’ may be used uninitialized in this function
clk-vt8500.c: In function ‘wm8850_find_pll_bits’:
clk-vt8500.c:560:12: ‘best_div2’ may be used uninitialized in this function
clk-vt8500.c:559:12: ‘best_div1’ may be used uninitialized in this function
clk-vt8500.c:558:14: ‘best_mul’ may be used uninitialized in this function
As the local variables are only use for temporaries, we can just
as well assign the final values directly, which also makes the
code slightly shorter.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Roman Volkov <rvolkov@v1ros.org>
---
drivers/clk/clk-vt8500.c | 34 ++++++++++------------------------
1 file changed, 10 insertions(+), 24 deletions(-)
diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c
index b0f76a84f1e9..d5a3453970d0 100644
--- a/drivers/clk/clk-vt8500.c
+++ b/drivers/clk/clk-vt8500.c
@@ -388,7 +388,6 @@ static int wm8650_find_pll_bits(unsigned long rate, unsigned long parent_rate,
{
u32 mul, div1;
int div2;
- u32 best_mul, best_div1, best_div2;
unsigned long tclk, rate_err, best_err;
best_err = (unsigned long)-1;
@@ -411,9 +410,9 @@ static int wm8650_find_pll_bits(unsigned long rate, unsigned long parent_rate,
if (rate_err < best_err) {
best_err = rate_err;
- best_mul = mul;
- best_div1 = div1;
- best_div2 = div2;
+ *multiplier = mul;
+ *divisor1 = div1;
+ *divisor2 = div2;
}
}
@@ -425,10 +424,6 @@ static int wm8650_find_pll_bits(unsigned long rate, unsigned long parent_rate,
/* if we got here, it wasn't an exact match */
pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
rate - best_err);
- *multiplier = best_mul;
- *divisor1 = best_div1;
- *divisor2 = best_div2;
-
return 0;
}
@@ -464,7 +459,6 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
{
u32 mul;
int div1, div2;
- u32 best_mul, best_div1, best_div2;
unsigned long tclk, rate_err, best_err;
best_err = (unsigned long)-1;
@@ -488,9 +482,9 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
if (rate_err < best_err) {
best_err = rate_err;
- best_mul = mul;
- best_div1 = div1;
- best_div2 = div2;
+ *multiplier = mul;
+ *divisor1 = div1;
+ *divisor2 = div2;
}
}
@@ -503,10 +497,7 @@ static int wm8750_find_pll_bits(unsigned long rate, unsigned long parent_rate,
pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
rate - best_err);
- *filter = wm8750_get_filter(parent_rate, best_div1);
- *multiplier = best_mul;
- *divisor1 = best_div1;
- *divisor2 = best_div2;
+ *filter = wm8750_get_filter(parent_rate, *divisor1);
return 0;
}
@@ -516,7 +507,6 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
{
u32 mul;
int div1, div2;
- u32 best_mul, best_div1, best_div2;
unsigned long tclk, rate_err, best_err;
best_err = (unsigned long)-1;
@@ -540,9 +530,9 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
if (rate_err < best_err) {
best_err = rate_err;
- best_mul = mul;
- best_div1 = div1;
- best_div2 = div2;
+ *multiplier = mul;
+ *divisor1 = div1;
+ *divisor2 = div2;
}
}
@@ -555,10 +545,6 @@ static int wm8850_find_pll_bits(unsigned long rate, unsigned long parent_rate,
pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
rate - best_err);
- *multiplier = best_mul;
- *divisor1 = best_div1;
- *divisor2 = best_div2;
-
return 0;
}
--
2.8.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v2 2/2] clk: vt8500: rework wm8650_find_pll_bits()
2016-06-07 21:56 [PATCH v2 0/2] Rework clk/vt8500 wm8650_find_pll_bits() Roman Volkov
2016-06-07 21:56 ` [PATCH v2 1/2] clk: vt8500: fix gcc-4.9 warnings Roman Volkov
@ 2016-06-07 21:56 ` Roman Volkov
2016-06-21 0:48 ` Stephen Boyd
1 sibling, 1 reply; 5+ messages in thread
From: Roman Volkov @ 2016-06-07 21:56 UTC (permalink / raw)
To: Stephen Boyd
Cc: Arnd Bergmann, linux-clk, linux-kernel, Michael Turquette,
Roman Volkov, Tony Prisk
From: Roman Volkov <rvolkov@v1ros.org>
PLL clock on WM8650 is calculated in the following way:
M * parent [O1] => / P [O2] => / D [O3]
Where O2 is 600MHz >= (M * parent) / P >= 300MHz.
Current algorithm does not met this requirement, so that the
function may return rates which are not supported by the hardware.
This patch fixes the algorithm and simplifies the code, reducing
the calculation time by ~10000 times (according to usermode app) by
removing the nested loops.
Signed-off-by: Roman Volkov <rvolkov@v1ros.org>
---
drivers/clk/clk-vt8500.c | 73 +++++++++++++++++++++++++-----------------------
1 file changed, 38 insertions(+), 35 deletions(-)
diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c
index d5a3453970d0..37368a399ff9 100644
--- a/drivers/clk/clk-vt8500.c
+++ b/drivers/clk/clk-vt8500.c
@@ -383,47 +383,50 @@ static int vt8500_find_pll_bits(unsigned long rate, unsigned long parent_rate,
return 0;
}
-static int wm8650_find_pll_bits(unsigned long rate, unsigned long parent_rate,
- u32 *multiplier, u32 *divisor1, u32 *divisor2)
+/*
+ * M * parent [O1] => / P [O2] => / D [O3]
+ * Where O1 is 900MHz...3GHz;
+ * O2 is 600MHz >= (M * parent) / P >= 300MHz;
+ * M is 36...120 [25MHz parent]; D is 1 or 2 or 4 or 8.
+ * Possible ranges (O3):
+ * D = 8: 37,5MHz...75MHz
+ * D = 4: 75MHz...150MHz
+ * D = 2: 150MHz...300MHz
+ * D = 1: 300MHz...600MHz
+ */
+static int wm8650_find_pll_bits(unsigned long rate,
+ unsigned long parent_rate, u32 *multiplier, u32 *divisor1,
+ u32 *divisor2)
{
- u32 mul, div1;
- int div2;
- unsigned long tclk, rate_err, best_err;
-
- best_err = (unsigned long)-1;
+ unsigned long O1, min_err, rate_err;
- /* Find the closest match (lower or equal to requested) */
- for (div1 = 5; div1 >= 3; div1--)
- for (div2 = 3; div2 >= 0; div2--)
- for (mul = 3; mul <= 1023; mul++) {
- tclk = parent_rate * mul / (div1 * (1 << div2));
- if (tclk > rate)
- continue;
- /* error will always be +ve */
- rate_err = rate - tclk;
- if (rate_err == 0) {
- *multiplier = mul;
- *divisor1 = div1;
- *divisor2 = div2;
- return 0;
- }
+ if (!parent_rate || (rate < 37500000) || (rate > 600000000))
+ return -EINVAL;
- if (rate_err < best_err) {
- best_err = rate_err;
- *multiplier = mul;
- *divisor1 = div1;
- *divisor2 = div2;
- }
- }
+ *divisor2 = rate <= 75000000 ? 3 : rate <= 150000000 ? 2 :
+ rate <= 300000000 ? 1 : 0;
+ /*
+ * Divisor P cannot be calculated. Test all divisors and find where M
+ * will be as close as possible to the requested rate.
+ */
+ min_err = ULONG_MAX;
+ for (*divisor1 = 5; *divisor1 >= 3; (*divisor1)--) {
+ O1 = rate * *divisor1 * (1 << (*divisor2));
+ rate_err = O1 % parent_rate;
+ if (rate_err < min_err) {
+ *multiplier = O1 / parent_rate;
+ if (rate_err == 0)
+ return 0;
+
+ min_err = rate_err;
+ }
+ }
- if (best_err == (unsigned long)-1) {
- pr_warn("%s: impossible rate %lu\n", __func__, rate);
+ if ((*multiplier < 3) || (*multiplier > 1023))
return -EINVAL;
- }
- /* if we got here, it wasn't an exact match */
- pr_warn("%s: requested rate %lu, found rate %lu\n", __func__, rate,
- rate - best_err);
+ pr_warn("%s: rate error is %lu\n", __func__, min_err);
+
return 0;
}
--
2.8.3
^ permalink raw reply related [flat|nested] 5+ messages in thread