From: "Jernej Škrabec" <jernej.skrabec@gmail.com>
To: Frank Oltmanns <frank@oltmanns.dev>
Cc: "Michael Turquette" <mturquette@baylibre.com>,
"Stephen Boyd" <sboyd@kernel.org>, "Chen-Yu Tsai" <wens@csie.org>,
"Samuel Holland" <samuel@sholland.org>,
"Guido Günther" <agx@sigxcpu.org>,
"Purism Kernel Team" <kernel@puri.sm>,
"Ondrej Jirman" <megi@xff.cz>,
"Neil Armstrong" <neil.armstrong@linaro.org>,
"Jessica Zhang" <quic_jesszhan@quicinc.com>,
"Sam Ravnborg" <sam@ravnborg.org>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Maxime Ripard" <mripard@kernel.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"David Airlie" <airlied@gmail.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 4/5] clk: sunxi-ng: a64: Add constraints on PLL-VIDEO0's n/m ratio
Date: Tue, 09 Jan 2024 21:29:39 +0100 [thread overview]
Message-ID: <3461075.QJadu78ljV@jernej-laptop> (raw)
In-Reply-To: <87jzoug2jz.fsf@oltmanns.dev>
Dne nedelja, 31. december 2023 ob 10:10:40 CET je Frank Oltmanns napisal(a):
>
> On 2023-12-19 at 17:54:19 +0100, Jernej Škrabec <jernej.skrabec@gmail.com> wrote:
> > Dne ponedeljek, 18. december 2023 ob 14:35:22 CET je Frank Oltmanns napisal(a):
> >> The Allwinner A64 manual lists the following constraint for the
> >> PLL-VIDEO0 clock: 8 <= N/M <= 25
> >>
> >> Use this constraint.
> >>
> >> Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
> >> ---
> >> drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 8 ++++++--
> >> 1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> >> index c034ac027d1c..75d839da446c 100644
> >> --- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> >> +++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> >> @@ -68,7 +68,8 @@ static SUNXI_CCU_NM_WITH_SDM_GATE_LOCK(pll_audio_base_clk, "pll-audio-base",
> >> BIT(28), /* lock */
> >> CLK_SET_RATE_UNGATE);
> >>
> >> -static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_CLOSEST(pll_video0_clk, "pll-video0",
> >> +static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_FEAT_NM_RATIO(pll_video0_clk,
> >> + "pll-video0",
> >> "osc24M", 0x010,
> >> 192000000, /* Minimum rate */
> >> 1008000000, /* Maximum rate */
>
> I just realized that adding the whole ratio limits for ccu_nm is
> superfluous as you could just as well express them in for of a minimum
> and maximum range:
> Since 8 <= N/M <= 25 and parent_rate = 24 MHz, therefore
> 192 MHz <= rate <= 600 MHz.
Good point!
>
> These absolute limits are also listed in Allwinner's A64 manual.
>
> BUT, here the upper limit was raised to 1008 MHz:
> 5de39acaf34604bd04834f092479cf4dcc946dd "clk: sunxi-ng: a64: Add max.
> rate constraint to video PLL"
>
> With this upper limit the ratio limitation is effectively:
> 8 <= N/M <= 42
>
> Icenowy Zheng (added to CC) had the reasonable explanation that this was
> used in the BSP kernel, so we should probably stick to that and ditch
> the two PLL-VIDEO0 related patches. What are your thoughts on that?
Ok, it seems that these patches are really superfluous. Remove them for v2.
Best regards,
Jernej
>
> >> @@ -80,7 +81,10 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_CLOSEST(pll_video0_clk, "pll-vid
> >> 297000000, /* frac rate 1 */
> >> BIT(31), /* gate */
> >> BIT(28), /* lock */
> >> - CLK_SET_RATE_UNGATE);
> >> + CLK_SET_RATE_UNGATE,
> >> + CCU_FEATURE_FRACTIONAL |
> >> + CCU_FEATURE_CLOSEST_RATE,
> >
> > Above flags are unrelated change, put them in new patch if needed.
> >
> > Best regards,
> > Jernej
> >
> >> + 8, 25); /* min/max nm ratio */
> >>
> >> static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_ve_clk, "pll-ve",
> >> "osc24M", 0x018,
> >>
> >>
>
next prev parent reply other threads:[~2024-01-09 20:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-18 13:35 [PATCH 0/5] Pinephone video out fixes (flipping between two frames) Frank Oltmanns
2023-12-18 13:35 ` [PATCH 1/5] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate Frank Oltmanns
2023-12-18 17:26 ` Frank Oltmanns
2023-12-19 16:46 ` Jernej Škrabec
2023-12-20 6:58 ` Frank Oltmanns
2023-12-20 15:09 ` Jernej Škrabec
2023-12-18 13:35 ` [PATCH 2/5] clk: sunxi-ng: a64: Add constraints on PLL-MIPI's n/m " Frank Oltmanns
2023-12-19 16:46 ` Jernej Škrabec
2023-12-18 13:35 ` [PATCH 3/5] clk: sunxi-ng: nm: Support constraints on " Frank Oltmanns
2023-12-19 16:52 ` Jernej Škrabec
2023-12-18 13:35 ` [PATCH 4/5] clk: sunxi-ng: a64: Add constraints on PLL-VIDEO0's n/m ratio Frank Oltmanns
2023-12-19 16:54 ` Jernej Škrabec
2023-12-20 7:09 ` Frank Oltmanns
2023-12-20 15:12 ` Jernej Škrabec
2023-12-22 7:46 ` Frank Oltmanns
2023-12-31 9:10 ` Frank Oltmanns
2024-01-09 20:29 ` Jernej Škrabec [this message]
2023-12-18 13:35 ` [PATCH 5/5] drm/panel: st7703: Drive XBD599 panel at higher clock rate Frank Oltmanns
2023-12-19 17:04 ` Jernej Škrabec
2023-12-20 7:14 ` Frank Oltmanns
2023-12-20 15:18 ` Jernej Škrabec
2023-12-20 18:57 ` Frank Oltmanns
2023-12-22 9:10 ` Frank Oltmanns
2023-12-22 17:36 ` Jernej Škrabec
2023-12-30 21:17 ` Frank Oltmanns
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