linux-kernel - Re: [linux-sunxi] [PATCH 10/13] [NOT FOR REVIEW NOW] clk: sunxi: Add CLK_SET_RATE

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Message-ID: <E50F5E8C-2121-493C-A7B2-D1535E916471@aosc.io>
Date:   Fri, 04 Aug 2017 17:03:03 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     Jernej Škrabec <jernej.skrabec@...l.net>,
        linux-sunxi@...glegroups.com, wens@...e.org
CC:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [linux-sunxi] [PATCH 10/13] [NOT FOR REVIEW NOW] clk: sunxi: Add CLK_SET_RATE_PARENT flag for H3 HDMI clock



于 2017年8月4日 GMT+08:00 下午4:59:03, "Jernej Škrabec" <jernej.skrabec@...l.net> 写到:
>Hi Chen-Yu,
>
>Dne petek, 04. avgust 2017 ob 06:29:50 CEST je Chen-Yu Tsai napisal(a):
>> On Fri, Aug 4, 2017 at 12:16 PM, Icenowy Zheng <icenowy@...c.io>
>wrote:
>> > 于 2017年8月4日 GMT+08:00 下午12:15:27, Chen-Yu Tsai <wens@...e.org> 写到:
>> >>Hi,
>> >>
>> >>On Tue, Aug 1, 2017 at 9:13 PM, Icenowy Zheng <icenowy@...c.io>
>wrote:
>> >>> From: Jernej Skrabec <jernej.skrabec@...l.net>
>> >>> 
>> >>> When setting the HDMI clock of H3, the PLL_VIDEO clock needs to
>be
>> >>
>> >>set.
>> >>
>> >>> Add CLK_SET_RATE_PARENT flag for H3 HDMI clock.
>> >>> 
>> >>> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
>> >>> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
>> >>> ---
>> >>> 
>> >>>  drivers/clk/sunxi-ng/ccu-sun8i-h3.c | 2 +-
>> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> >>> 
>> >>> diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
>> >>
>> >>b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
>> >>
>> >>> index b1127e8629d9..2ebb3d865b01 100644
>> >>> --- a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
>> >>> +++ b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
>> >>> @@ -474,7 +474,7 @@ static SUNXI_CCU_GATE(avs_clk,
>> >>
>> >>"avs",          "osc24M",
>> >>
>> >>>  static const char * const hdmi_parents[] = { "pll-video" };
>> >>>  static SUNXI_CCU_M_WITH_MUX_GATE(hdmi_clk, "hdmi", hdmi_parents,
>> >>> 
>> >>> -                                0x150, 0, 4, 24, 2, BIT(31), 0);
>> >>> +                                0x150, 0, 4, 24, 2, BIT(31),
>> >>
>> >>CLK_SET_RATE_PARENT);
>> >>
>> >>Line is longer than 80 characters.
>> >>
>> >>This looks independent enough so I've merged this for 4.14 with the
>> >>offending line wrapped and the following tag added:
>> >>
>> >>Fixes: 0577e4853bfb ("clk: sunxi-ng: Add H3 clocks")
>> >>
>> > Please don't merge this now until Jernej send it.
>> 
>> (Dropped Rob, devicetree and dri mailing lists)
>> 
>> Hi Jernej,
>> 
>> Is it OK if we take this patch for the next release? Or rather,
>> if there anything blocking this patch?
>
>I just made last check now and this patch is indeed OK. Before merging,
>please 
>read explanation below.
>
>Background:
>According to H3 datasheet and BSP driver, HDMI clock has M factor
>(divider) to 
>correctly set pixel clock to desired value. However, Jens Kuske
>discovered 
>that this factor doesn't play any role whatsoever and instead, division
>factor 
>set in PHY registers is the important one. I confirmed that on BSP
>kernel by 
>tying M factor to 0. Both, HDMI video and audio, still worked
>correctly.
>
>So that flag is necessary to set pll-video to pixel clock * div factor.
>I can 
>also change HDMI clock type to SUNXI_CCU_GATE (without M factor) and
>document 
>discrepancy with datasheet in ccu-sun8i-h3.c. Alternatively to this
>patch, 
>just in case, to be on the safe side, I can add pll-video clock phandle
>to the 
>dt node. However, as far as I know, that might prevent selecting
>another 
>parent on SoCs where HDMI clock has multiple parents.

Unfortunately A64 is this situation -- A64 TCON1/HDMI clocks can
use pll-video0/1 as parent, but TCON0 can only use pll-video0 or
pll-mipi (also a downstream clock of pll-video0), and by default
TCON1/HDMI also uses pll-video0.

Because of this I have never succeeded in multihead (LCD+HDMI)
on Pinebook.

>
>Regards,
>Jernej
>
>> 
>> Thanks
>> ChenYu
>> 
>> >>ChenYu
>> >>
>> >>>  static SUNXI_CCU_GATE(hdmi_ddc_clk,    "hdmi-ddc",     "osc24M",
>> >>>  
>> >>>                       0x154, BIT(31), 0);
>> >>> 
>> >>> --
>> >>> 2.13.0
>> >>> 
>> >>> --
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>> >>
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