[PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[Sylwester Nawrocki]

This patch fixes values of the EPLL K coefficient and changes
the EPLL output frequency values to match exactly what is
possible to achieve with given M, P, S, K coefficients.
This allows to avoid rounding errors and unexpected frequency
being set with clk_set_rate(), due to recalc_rate returning
different values than the PLL rate specified in the
exynos5420_epll_24mhz_tbl table. E.g. this prevents a case
where two consecutive clk_set_rate() calls with same argument
result in different PLL output frequency.

The PLL output frequencies have been calculated with formula:

f = fxtal * (M * 2^16 + K) / (P * 2^S) / 2^16

where fxtal = 24000000.

Fixes: 9842452acd ("clk: samsung: exynos542x: Add EPLL rate table")
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
---
 drivers/clk/samsung/clk-exynos5420.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos5420.c b/drivers/clk/samsung/clk-exynos5420.c
index 0748a0b..9a6476a 100644
--- a/drivers/clk/samsung/clk-exynos5420.c
+++ b/drivers/clk/samsung/clk-exynos5420.c
@@ -1283,16 +1283,16 @@ static void __init exynos5420_clk_sleep_init(void) {}
 static const struct samsung_pll_rate_table exynos5420_epll_24mhz_tbl[] = {
 	PLL_36XX_RATE(600000000U, 100, 2, 1, 0),
 	PLL_36XX_RATE(400000000U, 200, 3, 2, 0),
-	PLL_36XX_RATE(393216000U, 197, 3, 2, 25690),
-	PLL_36XX_RATE(361267200U, 301, 5, 2, 3671),
+	PLL_36XX_RATE(393216003U, 197, 3, 2, -25690),
+	PLL_36XX_RATE(361267218U, 301, 5, 2, 3671),
 	PLL_36XX_RATE(200000000U, 200, 3, 3, 0),
-	PLL_36XX_RATE(196608000U, 197, 3, 3, -25690),
-	PLL_36XX_RATE(180633600U, 301, 5, 3, 3671),
-	PLL_36XX_RATE(131072000U, 131, 3, 3, 4719),
+	PLL_36XX_RATE(196608001U, 197, 3, 3, -25690),
+	PLL_36XX_RATE(180633609U, 301, 5, 3, 3671),
+	PLL_36XX_RATE(131072006U, 131, 3, 3, 4719),
 	PLL_36XX_RATE(100000000U, 200, 3, 4, 0),
-	PLL_36XX_RATE(65536000U, 131, 3, 4, 4719),
-	PLL_36XX_RATE(49152000U, 197, 3, 5, 25690),
-	PLL_36XX_RATE(32768000U, 131, 3, 5, 4719),
+	PLL_36XX_RATE( 65536003U, 131, 3, 4, 4719),
+	PLL_36XX_RATE( 49152000U, 197, 3, 5, -25690),
+	PLL_36XX_RATE( 32768001U, 131, 3, 5, 4719),
 };
 
 static struct samsung_pll_clock exynos5x_plls[nr_plls] __initdata = {
-- 
1.9.1

Re: [PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[Sylwester Nawrocki]

On 07/21/2017 01:19 PM, Sylwester Nawrocki wrote:
> This patch fixes values of the EPLL K coefficient and changes
> the EPLL output frequency values to match exactly what is
> possible to achieve with given M, P, S, K coefficients.
> This allows to avoid rounding errors and unexpected frequency
> being set with clk_set_rate(), due to recalc_rate returning
> different values than the PLL rate specified in the
> exynos5420_epll_24mhz_tbl table. E.g. this prevents a case
> where two consecutive clk_set_rate() calls with same argument
> result in different PLL output frequency.
> 
> The PLL output frequencies have been calculated with formula:
> 
> f = fxtal * (M * 2^16  + K) / (P * 2^S) / 2^16
> 
> where fxtal = 24000000.
> 
> Fixes: 9842452acd ("clk: samsung: exynos542x: Add EPLL rate table")
> Signed-off-by: Sylwester Nawrocki<s.nawrocki@samsung.com>

Stephen, Mike,

Could you apply this patch directly for v4.12-rcX?
It fixes code added in v4.12.

-- 
Thanks,
Sylwester

Re: [PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[Stephen Boyd]

On 07/31, Sylwester Nawrocki wrote:
> On 07/21/2017 01:19 PM, Sylwester Nawrocki wrote:
> >This patch fixes values of the EPLL K coefficient and changes
> >the EPLL output frequency values to match exactly what is
> >possible to achieve with given M, P, S, K coefficients.
> >This allows to avoid rounding errors and unexpected frequency
> >being set with clk_set_rate(), due to recalc_rate returning
> >different values than the PLL rate specified in the
> >exynos5420_epll_24mhz_tbl table. E.g. this prevents a case
> >where two consecutive clk_set_rate() calls with same argument
> >result in different PLL output frequency.
> >
> >The PLL output frequencies have been calculated with formula:
> >
> >f = fxtal * (M * 2^16  + K) / (P * 2^S) / 2^16
> >
> >where fxtal = 24000000.
> >
> >Fixes: 9842452acd ("clk: samsung: exynos542x: Add EPLL rate table")
> >Signed-off-by: Sylwester Nawrocki<s.nawrocki@samsung.com>
> 
> Stephen, Mike,
> 
> Could you apply this patch directly for v4.12-rcX?
> It fixes code added in v4.12.
> 

You mean v4.13? Sure.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[Sylwester Nawrocki]

On 07/31/2017 10:17 PM, Stephen Boyd wrote:
> On 07/31, Sylwester Nawrocki wrote:
>> On 07/21/2017 01:19 PM, Sylwester Nawrocki wrote:
>>> This patch fixes values of the EPLL K coefficient and changes
>>> the EPLL output frequency values to match exactly what is
>>> possible to achieve with given M, P, S, K coefficients.
>>> This allows to avoid rounding errors and unexpected frequency
>>> being set with clk_set_rate(), due to recalc_rate returning
>>> different values than the PLL rate specified in the
>>> exynos5420_epll_24mhz_tbl table. E.g. this prevents a case
>>> where two consecutive clk_set_rate() calls with same argument
>>> result in different PLL output frequency.
>>>
>>> The PLL output frequencies have been calculated with formula:
>>>
>>> f = fxtal * (M * 2^16   + K) / (P * 2^S) / 2^16
>>>
>>> where fxtal = 24000000.
>>>
>>> Fixes: 9842452acd ("clk: samsung: exynos542x: Add EPLL rate table")
>>> Signed-off-by: Sylwester Nawrocki<s.nawrocki@samsung.com>
>> Stephen, Mike,
>>
>> Could you apply this patch directly for v4.12-rcX?
>> It fixes code added in v4.12.
>>
> You mean v4.13? Sure.

Yes, apologies for confusing these numbers. Thanks for taking
care of the patch.

-- 
Regards,
Sylwester

Re: [PATCH] clk: samsung: exynos5420: The EPLL rate table corrections

[Stephen Boyd]

On 07/21, Sylwester Nawrocki wrote:
> This patch fixes values of the EPLL K coefficient and changes
> the EPLL output frequency values to match exactly what is
> possible to achieve with given M, P, S, K coefficients.
> This allows to avoid rounding errors and unexpected frequency
> being set with clk_set_rate(), due to recalc_rate returning
> different values than the PLL rate specified in the
> exynos5420_epll_24mhz_tbl table. E.g. this prevents a case
> where two consecutive clk_set_rate() calls with same argument
> result in different PLL output frequency.
> 
> The PLL output frequencies have been calculated with formula:
> 
> f = fxtal * (M * 2^16 + K) / (P * 2^S) / 2^16
> 
> where fxtal = 24000000.
> 
> Fixes: 9842452acd ("clk: samsung: exynos542x: Add EPLL rate table")
> Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
> ---

Applied to clk-fixes

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project