linux-kernel - Re: [PATCH v3 3/8] clk: samsung: add BPLL rate table for Exynos 5422 SoC

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Date:   Fri, 1 Feb 2019 14:56:00 +0100
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Cc:     b.zolnierkie@...sung.com, krzk@...nel.org, kgene@...nel.org,
        kyungmin.park@...sung.com, m.szyprowski@...sung.com,
        s.nawrocki@...sung.com, myungjoo.ham@...sung.com,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 3/8] clk: samsung: add BPLL rate table for Exynos
 5422 SoC

Hi Chanwoo,

On 2/1/19 9:44 AM, Chanwoo Choi wrote:
> Hi,
> 
> On 19. 1. 31. 오후 5:49, Lukasz Luba wrote:
>> Add new table rate for BPLL for Exynos5422 SoC supporting Dynamic Memory
>> Controller frequencies for driver's DRAM timings.
>>
>> CC: Sylwester Nawrocki <s.nawrocki@...sung.com>
>> CC: Chanwoo Choi <cw00.choi@...sung.com>
>> CC: Michael Turquette <mturquette@...libre.com>
>> CC: Stephen Boyd <sboyd@...nel.org>
>> CC: Kukjin Kim <kgene@...nel.org>
>> CC: Krzysztof Kozlowski <krzk@...nel.org>
>> CC: linux-samsung-soc@...r.kernel.org
>> CC: linux-clk@...r.kernel.org
>> CC: linux-arm-kernel@...ts.infradead.org
>> CC: linux-kernel@...r.kernel.org
>> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
>> ---
>>   drivers/clk/samsung/clk-exynos5420.c | 15 ++++++++++++++-
>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/samsung/clk-exynos5420.c b/drivers/clk/samsung/clk-exynos5420.c
>> index 3e87421..8bf9579 100644
>> --- a/drivers/clk/samsung/clk-exynos5420.c
>> +++ b/drivers/clk/samsung/clk-exynos5420.c
>> @@ -1325,6 +1325,19 @@ static const struct samsung_pll_rate_table exynos5420_pll2550x_24mhz_tbl[] __ini
>>   	PLL_35XX_RATE(24 * MHZ, 200000000,  200, 3, 3),
>>   };
>>   
>> +static const struct samsung_pll_rate_table exynos5422_bpll_rate_table[] = {
>> +	PLL_35XX_RATE(24 * MHZ, 933000000, 311, 4, 1),
>> +	PLL_35XX_RATE(24 * MHZ, 825000000, 275, 4, 1),
>> +	PLL_35XX_RATE(24 * MHZ, 728000000, 182, 3, 1),
>> +	PLL_35XX_RATE(24 * MHZ, 633000000, 211, 4, 1),
>> +	PLL_35XX_RATE(24 * MHZ, 543000000, 181, 2, 2),
>> +	PLL_35XX_RATE(24 * MHZ, 413000000, 413, 6, 2),
>> +	PLL_35XX_RATE(24 * MHZ, 275000000, 275, 3, 3),
>> +	PLL_35XX_RATE(24 * MHZ, 206000000, 206, 3, 3),
>> +	PLL_35XX_RATE(24 * MHZ, 165000000, 110, 2, 3),
>> +	PLL_35XX_RATE(24 * MHZ, 138000000, 184, 2, 4),
> 
> Except for 825Mhz, I can't find the target frequency
> on Exynos5422 TRM document. Usually, Exynos TRM specified
> the supported stable clocks. It means that undefined clocks
> are not stable as I knew. Where do you find them?
> 
> When I calculated the PLL frequency with PMS value, it is correct.
> But, just we need to check the reference of undefined clocks on TRM
> in order to guarantee the stable operation.
They values live in vendor code for Android.
I have tested the DMC & DDR with these ratios in stress scenarios
for a few days and it was stable.

> 
> Remove 933/138Mhz because exynos5433-dmc.c doesn't use 933Mhz and 138Mhz
> and also Exynos5422 TRM doesn't define 933/138Mhz on pll table.
OK, I will remove them.
> 
>> +};
>> +
>>   static const struct samsung_pll_rate_table exynos5420_epll_24mhz_tbl[] = {
>>   	PLL_36XX_RATE(24 * MHZ, 600000000U, 100, 2, 1, 0),
>>   	PLL_36XX_RATE(24 * MHZ, 400000000U, 200, 3, 2, 0),
>> @@ -1467,7 +1480,7 @@ static void __init exynos5x_clk_init(struct device_node *np,
>>   		exynos5x_plls[apll].rate_table = exynos5420_pll2550x_24mhz_tbl;
>>   		exynos5x_plls[epll].rate_table = exynos5420_epll_24mhz_tbl;
>>   		exynos5x_plls[kpll].rate_table = exynos5420_pll2550x_24mhz_tbl;
>> -		exynos5x_plls[bpll].rate_table = exynos5420_pll2550x_24mhz_tbl;
>> +		exynos5x_plls[bpll].rate_table = exynos5422_bpll_rate_table;
> 
> Exynos5422 used the same PLL table for apll, kpll, bpll and so on.
> You don't need to make the separate pll table. Just add new entries
> to exynos5420_pll2550x_24mhz_tbl table.
OK, I will extend the exynos5420_pll2550x_24mhz_tbl table.

In v4 patch set, it will be fixed.

Regards,
Lukasz
> 
>>   	}
>>   
>>   	samsung_clk_register_pll(ctx, exynos5x_plls, ARRAY_SIZE(exynos5x_plls),
>>
>