Subject: Re: [PATCH 1/9] clk: samsung: exynos5433: Add clock flag to support
 suspend-to-ram
To: Krzysztof Kozlowski <krzk@kernel.org>,
        Chanwoo Choi <cw00.choi@samsung.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>, kgene@kernel.org,
        Tomasz Figa <tomasz.figa@gmail.com>, chanwoo@kernel.org,
        Jaehoon Chung <jh80.chung@samsung.com>,
        Inki Dae <inki.dae@samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>, linux-clk@vger.kernel.org
From: Marek Szyprowski <m.szyprowski@samsung.com>
Message-id: <79ff6d0d-fd7f-08d0-0f10-f4531632c08a@samsung.com>
Date: Fri, 12 Jan 2018 14:24:05 +0100
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References: <CGME20180109075905epcas1p1486543d8fec46f47d9d5ac350d841337@epcas1p1.samsung.com>
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Sender: linux-kernel-owner@vger.kernel.org

Hi Krzysztof and Chanwoo,

On 2018-01-09 12:44, Krzysztof Kozlowski wrote:
> On Tue, Jan 9, 2018 at 8:58 AM, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>> This patch adds the CLK_IS_CRITICAL and CLK_IGNORE_UNUSED flag
>> to some clocks in order to avoid the hang-out in the suspend mode.
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> Cc: Tomasz Figa <tomasz.figa@gmail.com>
>> Cc: Michael Turquette <mturquette@baylibre.com>
>> Cc: Stephen Boyd <sboyd@codeaurora.org>
>> Cc: linux-clk@vger.kernel.org
>> ---
>>   drivers/clk/samsung/clk-exynos5433.c | 22 +++++++++++-----------
>>   1 file changed, 11 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
>> index db270908037a..3dc53cd0c730 100644
>> --- a/drivers/clk/samsung/clk-exynos5433.c
>> +++ b/drivers/clk/samsung/clk-exynos5433.c
>> @@ -583,25 +583,25 @@
>>                          CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>>          GATE(CLK_ACLK_CAM1_333, "aclk_cam1_333", "div_aclk_cam1_333",
>>                          ENABLE_ACLK_TOP, 13,
>> -                       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>> +                       CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_CAM1_400, "aclk_cam1_400", "div_aclk_cam1_400",
>>                          ENABLE_ACLK_TOP, 12,
>>                          CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_CAM1_552, "aclk_cam1_552", "div_aclk_cam1_552",
>>                          ENABLE_ACLK_TOP, 11,
>> -                       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>> +                       CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_CAM0_333, "aclk_cam0_333", "div_aclk_cam0_333",
>>                          ENABLE_ACLK_TOP, 10,
>> -                       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>> +                       CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_CAM0_400, "aclk_cam0_400", "div_aclk_cam0_400",
>>                          ENABLE_ACLK_TOP, 9,
>>                          CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_CAM0_552, "aclk_cam0_552", "div_aclk_cam0_552",
>>                          ENABLE_ACLK_TOP, 8,
>> -                       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>> +                       CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_ISP_DIS_400, "aclk_isp_dis_400", "div_aclk_isp_dis_400",
>>                          ENABLE_ACLK_TOP, 7,
>> -                       CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED, 0),
>> +                       CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_ACLK_ISP_400, "aclk_isp_400", "div_aclk_isp_400",
>>                          ENABLE_ACLK_TOP, 6,
>>                          CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>> @@ -624,11 +624,11 @@
>>
>>          /* ENABLE_SCLK_TOP_CAM1 */
>>          GATE(CLK_SCLK_ISP_SENSOR2, "sclk_isp_sensor2", "div_sclk_isp_sensor2_b",
>> -                       ENABLE_SCLK_TOP_CAM1, 7, 0, 0),
>> +                       ENABLE_SCLK_TOP_CAM1, 7, CLK_IGNORE_UNUSED, 0),
>>          GATE(CLK_SCLK_ISP_SENSOR1, "sclk_isp_sensor1", "div_sclk_isp_sensor1_b",
>>                          ENABLE_SCLK_TOP_CAM1, 6, 0, 0),
>>          GATE(CLK_SCLK_ISP_SENSOR0, "sclk_isp_sensor0", "div_sclk_isp_sensor0_b",
>> -                       ENABLE_SCLK_TOP_CAM1, 5, 0, 0),
>> +                       ENABLE_SCLK_TOP_CAM1, 5, CLK_IGNORE_UNUSED, 0),
> Marking this and few others related to ISP as ignore_unused or
> is_critical looks like a hacky workaround for wrong topology or
> missing clock users. The real cause should be fixed instead marking
> all the clocks as critical or ignore_unused.

I think that instead of using CLK_IGNORE_UNUSED / CLK_IS_CRITICAL 
workaround,
exynos5433 clk driver should simply use *_suspend_regs infrastructure.
See suspend_regs entry in samsung_cmu_info and similar solution in
exynos5420.c clk driver (see exynos5420_clk_suspend function).

There is no point guessing why those clocks have to be enabled for proper
suspend cycle and which client driver should handle it. The documentation
misses such information at all. Just handle it in clk driver internally
without exposing it to clock clients. We already do this in case of other
Exynos SoCs.

>
> Best regards,
> Krzysztof
>
>>          GATE(CLK_SCLK_ISP_MCTADC_CAM1, "sclk_isp_mctadc_cam1", "oscclk",
>>                          ENABLE_SCLK_TOP_CAM1, 4, 0, 0),
>>          GATE(CLK_SCLK_ISP_UART_CAM1, "sclk_isp_uart_cam1", "div_sclk_isp_uart",
>> @@ -636,7 +636,7 @@
>>          GATE(CLK_SCLK_ISP_SPI1_CAM1, "sclk_isp_spi1_cam1", "div_sclk_isp_spi1_b",
>>                          ENABLE_SCLK_TOP_CAM1, 1, 0, 0),
>>          GATE(CLK_SCLK_ISP_SPI0_CAM1, "sclk_isp_spi0_cam1", "div_sclk_isp_spi0_b",
>> -                       ENABLE_SCLK_TOP_CAM1, 0, 0, 0),
>> +                       ENABLE_SCLK_TOP_CAM1, 0, CLK_IGNORE_UNUSED, 0),
>>
>>          /* ENABLE_SCLK_TOP_DISP */
>>          GATE(CLK_SCLK_HDMI_SPDIF_DISP, "sclk_hdmi_spdif_disp",
>> @@ -654,7 +654,7 @@
>>                          ENABLE_SCLK_TOP_FSYS, 4, CLK_SET_RATE_PARENT, 0),
>>          GATE(CLK_SCLK_UFSUNIPRO_FSYS, "sclk_ufsunipro_fsys",
>>                          "div_sclk_ufsunipro", ENABLE_SCLK_TOP_FSYS,
>> -                       3, CLK_SET_RATE_PARENT, 0),
>> +                       3, CLK_SET_RATE_PARENT | CLK_IS_CRITICAL, 0),
>>          GATE(CLK_SCLK_USBHOST30_FSYS, "sclk_usbhost30_fsys",
>>                          "div_sclk_usbhost30", ENABLE_SCLK_TOP_FSYS,
>>                          1, CLK_SET_RATE_PARENT, 0),
>> @@ -2982,7 +2982,7 @@ static void __init exynos5433_cmu_peris_init(struct device_node *np)
>>          GATE(CLK_PCLK_AUD_SLIMBUS, "pclk_aud_slimbus", "div_aclk_aud",
>>                          ENABLE_PCLK_AUD, 6, 0, 0),
>>          GATE(CLK_PCLK_AUD_UART, "pclk_aud_uart", "div_aclk_aud",
>> -                       ENABLE_PCLK_AUD, 5, 0, 0),
>> +                       ENABLE_PCLK_AUD, 5, CLK_IS_CRITICAL, 0),
>>          GATE(CLK_PCLK_AUD_PCM, "pclk_aud_pcm", "div_aclk_aud",
>>                          ENABLE_PCLK_AUD, 4, 0, 0),
>>          GATE(CLK_PCLK_AUD_I2S, "pclk_aud_i2s", "div_aclk_aud",
>> @@ -3008,7 +3008,7 @@ static void __init exynos5433_cmu_peris_init(struct device_node *np)
>>          GATE(CLK_SCLK_AUD_SLIMBUS, "sclk_aud_slimbus", "div_sclk_aud_slimbus",
>>                          ENABLE_SCLK_AUD1, 4, 0, 0),
>>          GATE(CLK_SCLK_AUD_UART, "sclk_aud_uart", "div_sclk_aud_uart",
>> -                       ENABLE_SCLK_AUD1, 3, CLK_IGNORE_UNUSED, 0),
>> +                       ENABLE_SCLK_AUD1, 3, CLK_IS_CRITICAL, 0),
>>          GATE(CLK_SCLK_AUD_PCM, "sclk_aud_pcm", "div_sclk_aud_pcm",
>>                          ENABLE_SCLK_AUD1, 2, 0, 0),
>>          GATE(CLK_SCLK_I2S_BCLK, "sclk_i2s_bclk", "ioclk_i2s_bclk",
>> --
>> 1.9.1
>>
>
>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland