Re: [PATCH v6 1/8] drm/mediatek: recalculate hdmi phy clock of MT2701 by querying hardware

CK Hu
2019-03-21T03:23:10Z

Hi, Wangyan:

On Wed, 2019-03-06 at 18:07 +0800, CK Hu wrote:
> Hi, Wangyan:
>
> On Mon, 2019-02-25 at 10:09 +0800, wangyan wang wrote:
> > From: chunhui dai <chunhui.dai@mediatek.com>
> >
> > Recalculate the rate of this clock, by querying hardware.
> >
> > Signed-off-by: chunhui dai <chunhui.dai@mediatek.com>
> > Signed-off-by: wangyan wang <wangyan.wang@mediatek.com>
> > ---
> > drivers/gpu/drm/mediatek/mtk_hdmi_phy.c | 7 ++----
> > drivers/gpu/drm/mediatek/mtk_hdmi_phy.h | 3 +--
> > drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c | 35 ++++++++++++++++++++++++++
> > drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c | 8 ++++++
> > 4 files changed, 46 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > index 4ef9c57ffd44..13c5e65b9ead 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.c
> > @@ -29,12 +29,9 @@ long mtk_hdmi_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> > return rate;
> > }
> >
> > -unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > - unsigned long parent_rate)
> > +u32 mtk_hdmi_phy_read(struct mtk_hdmi_phy *hdmi_phy, u32 offset)
> > {
> > - struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > -
> > - return hdmi_phy->pll_rate;
> > + return readl(hdmi_phy->regs + offset);
> > }
> >
> > void mtk_hdmi_phy_clear_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > index f39b1fc66612..fdad8b17a915 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_phy.h
> > @@ -41,6 +41,7 @@ struct mtk_hdmi_phy {
> > unsigned int ibias_up;
> > };
> >
> > +u32 mtk_hdmi_phy_read(struct mtk_hdmi_phy *hdmi_phy, u32 offset);
> > void mtk_hdmi_phy_clear_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > u32 bits);
> > void mtk_hdmi_phy_set_bits(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > @@ -50,8 +51,6 @@ void mtk_hdmi_phy_mask(struct mtk_hdmi_phy *hdmi_phy, u32 offset,
> > struct mtk_hdmi_phy *to_mtk_hdmi_phy(struct clk_hw *hw);
> > long mtk_hdmi_pll_round_rate(struct clk_hw *hw, unsigned long rate,
> > unsigned long *parent_rate);
> > -unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > - unsigned long parent_rate);
> >
> > extern struct platform_driver mtk_hdmi_phy_driver;
> > extern struct mtk_hdmi_phy_conf mtk_hdmi_phy_8173_conf;
> > diff --git a/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > index fcc42dc6ea7f..b25c9dfc432a 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_mt2701_hdmi_phy.c
> > @@ -153,6 +153,41 @@ static int mtk_hdmi_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> > RG_HDMITX_DRV_IBIAS_MASK);
> > return 0;
> > }
> > +static unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > + unsigned long parent_rate)
> > +{
> > + struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > + unsigned long out_rate, val;
> > +
> > + val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON6)
> > + & RG_HTPLL_PREDIV_MASK) >> RG_HTPLL_PREDIV;
> > + switch (val) {
> > + case 0x00:
> > + out_rate = parent_rate;
> > + break;
> > + case 0x01:
> > + out_rate = parent_rate / 2;
> > + break;
> > + default:
> > + out_rate = parent_rate / 4;
> > + break;
> > + }
> > +
> > + val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON6)
> > + & RG_HTPLL_FBKDIV_MASK) >> RG_HTPLL_FBKDIV;
> > + out_rate *= (val + 1) * 2;
> > + val = (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2)
> > + & RG_HDMITX_TX_POSDIV_MASK);
> > +
> > + out_rate >>= (val >> RG_HDMITX_TX_POSDIV);
> > +
> > + if (mtk_hdmi_phy_read(hdmi_phy, HDMI_CON2) & RG_HDMITX_EN_TX_POSDIV)
> > + out_rate = out_rate / 5;
> > +
>
> All the register you read here is set in mtk_hdmi_pll_set_rate(), so I
> think you could determine the out_rate in mtk_hdmi_pll_set_rate().

As offline discuss, you mention that when
cat /sys/kernel/debug/ckl/clk_summary, mtk_hdmi_pll_recalc_rate() is
called, so read register to get the real clock. The clk_summary call
clk_core_get_rate() to get rate, and clk_core_get_rate() would check the
flag CLK_GET_RATE_NOCACHE to call __clk_recalc_rates(), but mtk_hdmi_phy
does not have this flag, so this function would not be called when
clk_summary. So I still think you could determine the out_rate in
mtk_hdmi_pll_set_rate().

Regards,
CK

>
> Regards,
> CK
>
> > + hdmi_phy->pll_rate = out_rate;
> > +
> > + return hdmi_phy->pll_rate;
> > +}
> >
> > static const struct clk_ops mtk_hdmi_phy_pll_ops = {
> > .prepare = mtk_hdmi_pll_prepare,
> > diff --git a/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c b/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > index ed5916b27658..cb23c1e4692a 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c
> > @@ -285,6 +285,14 @@ static int mtk_hdmi_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> > return 0;
> > }
> >
> > +static unsigned long mtk_hdmi_pll_recalc_rate(struct clk_hw *hw,
> > + unsigned long parent_rate)
> > +{
> > + struct mtk_hdmi_phy *hdmi_phy = to_mtk_hdmi_phy(hw);
> > +
> > + return hdmi_phy->pll_rate;
> > +}
> > +
> > static const struct clk_ops mtk_hdmi_phy_pll_ops = {
> > .prepare = mtk_hdmi_pll_prepare,
> > .unprepare = mtk_hdmi_pll_unprepare,
>

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