Date:   Fri, 04 May 2018 16:15:12 +0530
From:   Amit Nischal <anischal@...eaurora.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        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,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 3/3] clk: qcom: Add Global Clock controller (GCC)
 driver for SDM845

On 2018-05-02 12:53, Stephen Boyd wrote:
> Quoting Amit Nischal (2018-04-30 09:20:10)
>> ---
>>  .../devicetree/bindings/clock/qcom,gcc.txt         |    1 +
>>  drivers/clk/qcom/Kconfig                           |   10 +-
>>  drivers/clk/qcom/Makefile                          |    1 +
>>  drivers/clk/qcom/gcc-sdm845.c                      | 3480 
>> ++++++++++++++++++++
>>  include/dt-bindings/clock/qcom,gcc-sdm845.h        |  239 ++
> 
> Do the split that Rob suggests please, given that you're resending. And
> also include his reviewed-by tag.

Thanks for the review. Sure I will split the dt-binding into
separate patch in next series.

> 
>>  5 files changed, 3727 insertions(+), 4 deletions(-)
>>  create mode 100644 drivers/clk/qcom/gcc-sdm845.c
>>  create mode 100644 include/dt-bindings/clock/qcom,gcc-sdm845.h
>> 
>> diff --git a/drivers/clk/qcom/Kconfig b/drivers/clk/qcom/Kconfig
>> index e42e1af..3298beb 100644
>> --- a/drivers/clk/qcom/Kconfig
>> +++ b/drivers/clk/qcom/Kconfig
>> @@ -218,13 +218,15 @@ config MSM_MMCC_8996
>>           Say Y if you want to support multimedia devices such as 
>> display,
>>           graphics, video encode/decode, camera, etc.
>> 
>> -config MSM_GCC_8998
>> -       tristate "MSM8998 Global Clock Controller"
>> +config SDM_GCC_845
>> +       tristate "SDM845 Global Clock Controller"
>> +       select QCOM_GDSC
>>         depends on COMMON_CLK_QCOM
>>         help
>> -         Support for the global clock controller on msm8998 devices.
>> +         Support for the global clock controller on Qualcomm 
>> Technologies, Inc
>> +         sdm845 devices.
>>           Say Y if you want to use peripheral devices such as UART, 
>> SPI,
>> -         i2c, USB, UFS, SD/eMMC, PCIe, etc.
>> +         I2C, USB, UFS, SDDC, PCIe, etc.
> 
> This is all wrong.
> 

My bad. I did by mistake. Will fix this in next series.

>> 
>>  config SPMI_PMIC_CLKDIV
>>         tristate "SPMI PMIC clkdiv Support"
>> diff --git a/drivers/clk/qcom/gcc-sdm845.c 
>> b/drivers/clk/qcom/gcc-sdm845.c
>> new file mode 100644
>> index 0000000..6484cba
>> --- /dev/null
>> +++ b/drivers/clk/qcom/gcc-sdm845.c
>> @@ -0,0 +1,3480 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
>> + */
>> +
> [...]
>> +                       .name = "gcc_disp_axi_clk",
>> +                       .ops = &clk_branch2_ops,
>> +               },
>> +       },
>> +};
>> +
>> +static struct clk_branch gcc_disp_gpll0_clk_src = {
>> +       .halt_reg = 0x52004,
>> +       .halt_check = BRANCH_HALT_DELAY,
> 
> What about this one? It's not a phy so I'm confused again why we're
> unable to check the halt bit. To be clear(er), I don't see why we ever
> want to have HALT_DELAY used. Hopefully we can remove that flag.
> 
> From what I recall, the flag is there for clks that don't toggle their
> status bit at all, but that we know take a few cycles to ungate the
> upstream clk. So we threw a delay into the code to make sure that when
> clk_enable() returned, a driver wouldn't try to use hardware before the
> clk was actually on. But these cases should pretty much never happen,
> hence all the pushback against this flag.
> 

For these "*gpll0_clk_src" and "*gpll0_div_clk" clocks, there is no halt
bit to check the status and it is required to have delay for few cycles
so that clock gets turned on before a client driver to use the hardware.

>> +       .clkr = {
>> +               .enable_reg = 0x52004,
>> +               .enable_mask = BIT(18),
>> +               .hw.init = &(struct clk_init_data){
>> +                       .name = "gcc_disp_gpll0_clk_src",
>> +                       .parent_names = (const char *[]){
>> +                               "gpll0",
>> +                       },
>> +                       .num_parents = 1,
> [...]
>> +               .enable_reg = 0x7508c,
>> +               .enable_mask = BIT(0),
>> +               .hw.init = &(struct clk_init_data){
>> +                       .name = "gcc_ufs_card_phy_aux_clk",
>> +                       .parent_names = (const char *[]){
>> +                               "gcc_ufs_card_phy_aux_clk_src",
>> +                       },
>> +                       .num_parents = 1,
>> +                       .flags = CLK_SET_RATE_PARENT,
>> +                       .ops = &clk_branch2_ops,
>> +               },
>> +       },
>> +};
>> +
>> +static struct clk_branch gcc_ufs_card_rx_symbol_0_clk = {
>> +       .halt_reg = 0x75018,
>> +       .halt_check = BRANCH_HALT_DELAY,
> 
> There are still HALT_DELAY flags for UFS though? Why?

For ufs_card tx/rx symbol clocks, we don't poll the status bit as
per the recommendation from the HW team. We can change the halt_check
type to newly implemented flag "BRANCH_HALT_SKIP". Please update us with
your thoughts to change the flag to "BRANCH_HALT_SKIP".

> 
> Also, are you going to send DFS support for the QUP clks? I would like
> to see that code merged soon.

Taniya has sent the patches for DFS support for QUP clocks.
https://patchwork.kernel.org/patch/10376951/

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