Re: [PATCH V6 0/8] make mt7623 clock of hdmi stable

[CK Hu]

Hi, Wangyan:

On Wed, 2019-03-06 at 09:52 +0800, CK Hu wrote:
> On Mon, 2019-02-25 at 10:09 +0800, wangyan wang wrote:
> > From: Wangyan Wang <wangyan.wang@xxxxxxxxxxxx>
> > 
> > V6 adopt maintainer's suggestion.
> > Here is the change list between V5 & V6
> > 1. change "unsigned char mux_flags;" to "u8 mux_flags;" to
> > match with the struct in " clk: mediatek: add MUX_GATE_FLAGS_2".
> > 
> 
> Hi, Wangyan:
> 
> I'm not familiar with this clock system, so I still have some question
> about it, if you could describe more clear, it would help us to speed up
> this review process.
> 
> In [1], I find the clock that dpi and hdmi_phy controls,
> 
> 	dpi0: dpi@14014000 {
> 		clocks = <&mmsys CLK_MM_DPI1_DIGL>,
> 			 <&mmsys CLK_MM_DPI1_ENGINE>,
> 			 <&topckgen CLK_TOP_TVDPLL>;
> 		clock-names = "pixel", "engine", "pll";
> 	};
> 
> 
> 	hdmi_phy: phy@10209100 {
> 		clocks = <&apmixedsys CLK_APMIXED_HDMI_REF>;
> 		clock-names = "pll_ref";
> 	};
> 
> In [2], You say that to prevent changing tvdpll would let hdmi stable,
> and this clock is controlled by dpi, why do you modify the control flow
> in hdmi_phy? If these two have relationship, please describe more clear
> because I'm not familiar with this clock system.
> 

As discuss offline, in [3] we can find out that CLK_APMIXED_HDMI_REF is
derived from tvdpll, so tvdpll is the parent clock of hdmi_phy_pll.
Therefore, this series should modify hdmi_phy flow as well.

[3]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/clk/mediatek/clk-mt2701.c?h=v5.0#n973

Regards,
CK

> And I think that patch 'drm/mediatek: using new factor for tvdpll in
> MT2701' is the major patch to prevent modifying tvdpll because it reduce
> the factor case. Does MT8173 has the same problem? Just ask, I does not
> require you to modify MT8173 part.
> [1]
> https://github.com/frank-w/BPI-R2-4.14/blob/663f7def421952eb49b2d698eadaff12d02622d2/arch/arm/boot/dts/mt7623.dtsi
> [2]
> http://lists.infradead.org/pipermail/linux-mediatek/2019-February/017693.html
> 
> 
> Regards,
> CK
> 
> 
> > 
> > chunhui dai (8):
> >   drm/mediatek: recalculate hdmi phy clock of MT2701 by querying
> >     hardware
> >   drm/mediatek: move the setting of fixed divider
> >   drm/mediatek: using different flags of clk for HDMI phy
> >   drm/mediatek: fix the rate and divder of hdmi phy for MT2701
> >   clk: mediatek: add MUX_GATE_FLAGS_2
> >   clk: mediatek: using CLK_MUX_ROUND_CLOSEST for the clock of dpi1_sel
> >   drm/mediatek: using new factor for tvdpll in MT2701
> >   drm/mediatek: fix the rate of parent for hdmi phy in MT2701
> > 
> >  drivers/clk/mediatek/clk-mt2701.c              |  4 +-
> >  drivers/clk/mediatek/clk-mtk.c                 |  2 +-
> >  drivers/clk/mediatek/clk-mtk.h                 | 20 ++++++---
> >  drivers/gpu/drm/mediatek/mtk_dpi.c             |  8 ++--
> >  drivers/gpu/drm/mediatek/mtk_hdmi_phy.c        | 34 ++++------------
> >  drivers/gpu/drm/mediatek/mtk_hdmi_phy.h        |  7 +---
> >  drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c | 56 +++++++++++++++++++++++---
> >  drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c | 23 +++++++++++
> >  8 files changed, 102 insertions(+), 52 deletions(-)
> > 
>