linux-kernel - Re: [PATCH 2/2] clk: qcom: Add camera clock controller driver for SDM845

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Date:   Thu, 02 Aug 2018 09:57:58 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Amit Nischal <anischal@...eaurora.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Odelu Kukatla <okukatla@...eaurora.org>,
        Taniya Das <tdas@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-clk-owner@...r.kernel.org
Subject: Re: [PATCH 2/2] clk: qcom: Add camera clock controller driver for SDM845

Quoting Amit Nischal (2018-07-30 00:20:52)
> On 2018-07-26 22:52, Stephen Boyd wrote:
> > Quoting Amit Nischal (2018-07-23 04:26:33)
> >> diff --git a/drivers/clk/qcom/camcc-sdm845.c 
> >> b/drivers/clk/qcom/camcc-sdm845.c
> >> new file mode 100644
> >> index 0000000..61e5ec2
> >> --- /dev/null
> >> +++ b/drivers/clk/qcom/camcc-sdm845.c
> >> +static struct clk_rcg2 cam_cc_bps_clk_src = {
> >> +       .cmd_rcgr = 0x600c,
> >> +       .mnd_width = 0,
> >> +       .hid_width = 5,
> >> +       .parent_map = cam_cc_parent_map_0,
> >> +       .freq_tbl = ftbl_cam_cc_bps_clk_src,
> >> +       .clkr.hw.init = &(struct clk_init_data){
> >> +               .name = "cam_cc_bps_clk_src",
> >> +               .parent_names = cam_cc_parent_names_0,
> >> +               .num_parents = 6,
> >> +               .flags = CLK_SET_RATE_PARENT,
> >> +               .ops = &clk_rcg2_shared_ops,
> > 
> > Why are shared ops used in this driver?
> > 
> 
> As per HW design, most of the CAMCC RCGs needs to move to
> XO during clock disable so because of this we have used the
> shared ops.

Please add a comment to this effect in this driver and also mention this
in the commit text. I guess the camera firmware is also doing clk
control and so it wants the clk to be on at some basic rate in case
that's happening?
 
> >> +
> >> +static struct clk_rcg2 cam_cc_slow_ahb_clk_src = {
> >> +       .cmd_rcgr = 0x6054,
> >> +       .mnd_width = 0,
> >> +       .hid_width = 5,
> >> +       .parent_map = cam_cc_parent_map_0,
> >> +       .freq_tbl = ftbl_cam_cc_slow_ahb_clk_src,
> >> +       .clkr.hw.init = &(struct clk_init_data){
> >> +               .name = "cam_cc_slow_ahb_clk_src",
> >> +               .parent_names = cam_cc_parent_names_0,
> >> +               .num_parents = 6,
> >> +               .flags = CLK_SET_RATE_PARENT,
> > 
> > Is CLK_SET_RATE_PARENT intentionally set on these RCGs so that they can
> > reconfigure the PLL frequency? Wouldn't that be a fixed rate PLL
> > frequency?
> > 
> 
> PLL2_OUT_EVEN requires to be reconfigure to 480MHz so clock sources 
> which
> are using PLL2 in their frequency table requires 'CLK_SET_RATE_PARENT'
> flag to be set.

Ok.