RE: [PATCH] clk: samsung: fsd: Mark PLL_CAM_CSI as critical

Inbaraj E
2024-09-19T11:35:38Z

> -----Original Message-----
> From: Stephen Boyd <sboyd@kernel.org>
> Sent: 19 September 2024 15:51
> To: Inbaraj E <inbaraj.e@samsung.com>; alim.akhtar@samsung.com;
> cw00.choi@samsung.com; krzk@kernel.org; linux-clk@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-samsung-soc@vger.kernel.org;
> mturquette@baylibre.com; s.nawrocki@samsung.com
> Cc: pankaj.dubey@samsung.com; gost.dev@samsung.com; Inbaraj E
> <inbaraj.e@samsung.com>
> Subject: Re: [PATCH] clk: samsung: fsd: Mark PLL_CAM_CSI as critical
>
> Quoting Inbaraj E (2024-09-17 03:10:16)
> > PLL_CAM_CSI is the parent clock for the ACLK and PCLK in the
> > CMU_CAM_CSI block. When we gate ACLK or PCLK, the clock framework
> will
> > subsequently disables the parent clocks(PLL_CAM_CSI). Disabling
> > PLL_CAM_CSI is causing sytem level halt.
> >
> > It was observed on FSD SoC, when we gate the ACLK and PCLK during CSI
> > stop streaming through pm_runtime_put system is getting halted. So
> > marking PLL_CAM_CSI as critical to prevent disabling.
> >
> > Signed-off-by: Inbaraj E <inbaraj.e@samsung.com>
> > ---
>
> Please add a fixes tag. Although this is likely a band-aid fix because marking
> something critical leaves it enabled forever.

Sure, will add fixes tag. As per HW manual, this PLL_CAM_CSI is
supplying clock even for CMU SFR access of CSI block, so we can't
gate this.

>
> > drivers/clk/samsung/clk-fsd.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/clk/samsung/clk-fsd.c
> > b/drivers/clk/samsung/clk-fsd.c index 6f984cfcd33c..b1764aab9429
> > 100644
> > --- a/drivers/clk/samsung/clk-fsd.c
> > +++ b/drivers/clk/samsung/clk-fsd.c
> > @@ -1637,8 +1637,9 @@ static const struct samsung_pll_rate_table
> > pll_cam_csi_rate_table[] __initconst };
> >
> > static const struct samsung_pll_clock cam_csi_pll_clks[] __initconst = {
> > - PLL(pll_142xx, 0, "fout_pll_cam_csi", "fin_pll",
> > - PLL_LOCKTIME_PLL_CAM_CSI, PLL_CON0_PLL_CAM_CSI,
> pll_cam_csi_rate_table),
> > + __PLL(pll_142xx, 0, "fout_pll_cam_csi", "fin_pll",
> > + CLK_GET_RATE_NOCACHE | CLK_IS_CRITICAL,
> > + PLL_LOCKTIME_PLL_CAM_CSI,
>
> Please add a comment indicating that this clk can never turn off because
> <insert reason here>.

Sure, will post v2 after adding comment explaining reason behind
marking this clock as critical.

Regards,
Inbaraj E