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Date: Tue, 30 Jan 2024 09:52:03 -0800
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From: Unnathi Chalicheemala <quic_uchalich@quicinc.com>
Subject: Re: [PATCH 5/5] soc: qcom: llcc: Add regmap for Broadcast_AND region
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
CC: Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio
	<konrad.dybcio@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley
	<conor+dt@kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel@quicinc.com>
References: <cover.1706296015.git.quic_uchalich@quicinc.com>
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On 1/29/2024 2:03 PM, Dmitry Baryshkov wrote:
> On Mon, 29 Jan 2024 at 20:17, Unnathi Chalicheemala
> <quic_uchalich@quicinc.com> wrote:
>>
>>
>>
>> On 1/26/2024 12:29 PM, Dmitry Baryshkov wrote:
>>> On Fri, 26 Jan 2024 at 21:48, Unnathi Chalicheemala
>>> <quic_uchalich@quicinc.com> wrote:
>>>>
>>>> To support CSR programming, a broadcast interface is used to program
>>>> all channels in a single command. Until SM8450 there was only one
>>>> broadcast region (Broadcast_OR) used to broadcast write and check
>>>> for status bit 0. From SM8450 onwards another broadcast region
>>>> (Broadcast_AND) has been added which checks for status bit 1.
>>>>
>>>> Update llcc_drv_data structure with new regmap for Broadcast_AND
>>>> region and initialize regmap for Broadcast_AND region when HW block
>>>> version is greater than 4.1 for backwards compatibility.
>>>>
>>>> Switch from broadcast_OR to broadcast_AND region for checking
>>>> status bit 1 as Broadcast_OR region checks only for bit 0.
>>>
>>> This breaks backwards compatibility with the existing DT files, doesn't it?
>>>
>>
>> It shouldn't as checking for status bit 1 is happening only when the block
>> version is greater than 4.1, which is when Broadcast_AND region support
>> is added.
> 
> Let me reiterate, please: with the existing DT files. You are patching
> DT files in patches 2-4, but this is not enough. DT files are
> considered to be ABI. As such old DT files must continue to work with
> newer kernels.
>

I'm sorry, I think I'm not understanding this right.
 
>>
>>>> While at it, also check return value after reading Broadcast_OR
>>>> region in llcc_update_act_ctrl().
>>>
>>> Separate patch, Fixes tag.
>>>
>>
>> Ack. Will remove this from existing patch.
>> Thanks for the review Dmitry!
>>
>>>>
>>>> Signed-off-by: Unnathi Chalicheemala <quic_uchalich@quicinc.com>
>>>> ---
>>>>  drivers/soc/qcom/llcc-qcom.c       | 12 +++++++++++-
>>>>  include/linux/soc/qcom/llcc-qcom.h |  4 +++-
>>>>  2 files changed, 14 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
>>>> index 4ca88eaebf06..5a2dac2d4772 100644
>>>> --- a/drivers/soc/qcom/llcc-qcom.c
>>>> +++ b/drivers/soc/qcom/llcc-qcom.c
>>>> @@ -849,7 +849,7 @@ static int llcc_update_act_ctrl(u32 sid,
>>>>                 return ret;
>>>>
>>>>         if (drv_data->version >= LLCC_VERSION_4_1_0_0) {
>>>> -               ret = regmap_read_poll_timeout(drv_data->bcast_regmap, status_reg,
>>>> +               ret = regmap_read_poll_timeout(drv_data->bcast_and_regmap, status_reg,
>>>>                                       slice_status, (slice_status & ACT_COMPLETE),
>>>>                                       0, LLCC_STATUS_READ_DELAY);

Above if condition will be true only for SM8450, 8550 and 8650 - whose DT files have been changed.
It would never check for other existing DT files - I guess I'm failing to understand why the code
would break with other DeviceTree files.

>>>>                 if (ret)
>>>> @@ -859,6 +859,8 @@ static int llcc_update_act_ctrl(u32 sid,
>>>>         ret = regmap_read_poll_timeout(drv_data->bcast_regmap, status_reg,
>>>>                                       slice_status, !(slice_status & status),
>>>>                                       0, LLCC_STATUS_READ_DELAY);
>>>> +       if (ret)
>>>> +               return ret;
>>>>
>>>>         if (drv_data->version >= LLCC_VERSION_4_1_0_0)
>>>>                 ret = regmap_write(drv_data->bcast_regmap, act_clear_reg,
>>>> @@ -1282,6 +1284,14 @@ static int qcom_llcc_probe(struct platform_device *pdev)
>>>>
>>>>         drv_data->version = version;
>>>>
>>>> +       if (drv_data->version >= LLCC_VERSION_4_1_0_0) {
>>>> +               drv_data->bcast_and_regmap = qcom_llcc_init_mmio(pdev, i + 1, "llcc_broadcast_and_base");
>>>> +               if (IS_ERR(drv_data->bcast_and_regmap)) {
>>>> +                       ret = PTR_ERR(drv_data->bcast_and_regmap);
>>>> +                       goto err;
>>>> +               }
>>>> +       }

I have added a similar check in the probe function above; are you saying this too will break with
existing DT files? 

>>>> +
>>>>         llcc_cfg = cfg->sct_data;
>>>>         sz = cfg->size;
>>>>
>>>> diff --git a/include/linux/soc/qcom/llcc-qcom.h b/include/linux/soc/qcom/llcc-qcom.h
>>>> index 1a886666bbb6..9e9f528b1370 100644
>>>> --- a/include/linux/soc/qcom/llcc-qcom.h
>>>> +++ b/include/linux/soc/qcom/llcc-qcom.h
>>>> @@ -115,7 +115,8 @@ struct llcc_edac_reg_offset {
>>>>  /**
>>>>   * struct llcc_drv_data - Data associated with the llcc driver
>>>>   * @regmaps: regmaps associated with the llcc device
>>>> - * @bcast_regmap: regmap associated with llcc broadcast offset
>>>> + * @bcast_regmap: regmap associated with llcc broadcast OR offset
>>>> + * @bcast_and_regmap: regmap associated with llcc broadcast AND offset
>>>>   * @cfg: pointer to the data structure for slice configuration
>>>>   * @edac_reg_offset: Offset of the LLCC EDAC registers
>>>>   * @lock: mutex associated with each slice
>>>> @@ -129,6 +130,7 @@ struct llcc_edac_reg_offset {
>>>>  struct llcc_drv_data {
>>>>         struct regmap **regmaps;
>>>>         struct regmap *bcast_regmap;
>>>> +       struct regmap *bcast_and_regmap;
>>>>         const struct llcc_slice_config *cfg;
>>>>         const struct llcc_edac_reg_offset *edac_reg_offset;
>>>>         struct mutex lock;
>>>> --
>>>> 2.25.1
>>>>
>>>>
>>>
>>>
> 
> 
> 
--
Thanks & Warm Regards,
Unnathi