linux-kernel - Re: [PATCH 5/5] soc: qcom: llcc: Add regmap for Broadcast

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Message-ID: <CAA8EJprPZThviO0vZfyYz+YShPKxg9YcuOUUCv4B_ePghuB8XA@mail.gmail.com>
Date: Tue, 30 Jan 2024 20:57:38 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Unnathi Chalicheemala <quic_uchalich@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel@...cinc.com
Subject: Re: [PATCH 5/5] soc: qcom: llcc: Add regmap for Broadcast_AND region

On Tue, 30 Jan 2024 at 19:52, Unnathi Chalicheemala
<quic_uchalich@...cinc.com> wrote:
>
> On 1/29/2024 2:03 PM, Dmitry Baryshkov wrote:
> > On Mon, 29 Jan 2024 at 20:17, Unnathi Chalicheemala
> > <quic_uchalich@...cinc.com> wrote:
> >>
> >>
> >>
> >> On 1/26/2024 12:29 PM, Dmitry Baryshkov wrote:
> >>> On Fri, 26 Jan 2024 at 21:48, Unnathi Chalicheemala
> >>> <quic_uchalich@...cinc.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@...cinc.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.

I'm saying that the driver must continue to work (well, at least not
to crash) even if somebody runs the kernel with older DT.

>
> >>>>                 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



-- 
With best wishes
Dmitry