linux-kernel - Re: [PATCH v3 2/3] clk: qcom: dispcc-sm8650: add missing CLK_SET_RATE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <kxrhhb3vdojbnqfbwks2qmob55fwm3onleood73qfk6esl7g2c@q66kw5am4emc>
Date: Tue, 16 Jul 2024 19:46:28 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: neil.armstrong@...aro.org
Cc: Bjorn Andersson <andersson@...nel.org>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Taniya Das <quic_tdas@...cinc.com>, 
	linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] clk: qcom: dispcc-sm8650: add missing
 CLK_SET_RATE_PARENT flag

On Tue, Jul 16, 2024 at 03:46:24PM GMT, neil.armstrong@...aro.org wrote:
> On 16/07/2024 15:44, Dmitry Baryshkov wrote:
> > On Tue, 16 Jul 2024 at 15:32, Neil Armstrong <neil.armstrong@...aro.org> wrote:
> > > 
> > > On 16/07/2024 13:20, Dmitry Baryshkov wrote:
> > > > On Tue, Jul 16, 2024 at 11:05:22AM GMT, Neil Armstrong wrote:
> > > > > Add the missing CLK_SET_RATE_PARENT for the byte0_div_clk_src
> > > > > and byte1_div_clk_src, the clock rate should propagate to
> > > > > the corresponding _clk_src.
> > > > > 
> > > > > Fixes: 9e939f008338 ("clk: qcom: add the SM8650 Display Clock Controller driver")
> > > > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > > > > Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> > > > > ---
> > > > >    drivers/clk/qcom/dispcc-sm8650.c | 2 ++
> > > > >    1 file changed, 2 insertions(+)
> > > > 
> > > > This doesn't seem correct, the byte1_div_clk_src is a divisor, so the
> > > > rate should not be propagated. Other platforms don't set this flag.
> > > > 
> > > 
> > > Why not ? the disp_cc_mdss_byte1_clk_src has CLK_SET_RATE_PARENT and a div_table,
> > > and we only pass DISP_CC_MDSS_BYTE1_CLK to the dsi controller.
> > 
> > Yes, the driver sets byte_clk with the proper rate, then it sets
> > byte_intf_clk, which results in a proper divisor.
> > If we have CLK_SET_RATE_PARENT for byte1_div_clk_src, then setting
> > byte_intf_clk rate will also result in a rate change for the byte_clk
> > rate.
> > 
> > Note, all other platforms don't set that flag for this reason (I think
> > I had to remove it during sm8450 development for this reason).
> > 
> 
> Ack, I think this deserves a comment explaining this, I'll add it.

But where to place it? This applies to _all_ dispcc controllers.

-- 
With best wishes
Dmitry