linux-kernel - Re: [PATCH 1/3] ufs: ufs-qcom: Add support for DT-based gear and rate limiting

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Message-ID: <CAO9ioeWLLW1UgJfByBAXp9-v81AqmRV9Acs5Eae9k4Gkr1U0MA@mail.gmail.com>
Date: Thu, 24 Jul 2025 11:41:40 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Ram Kumar Dwivedi <quic_rdwivedi@...cinc.com>
Cc: mani@...nel.org, alim.akhtar@...sung.com, avri.altman@....com,
        bvanassche@....org, robh@...nel.org, krzk+dt@...nel.org,
        conor+dt@...nel.org, andersson@...nel.org, konradybcio@...nel.org,
        James.Bottomley@...senpartnership.com, martin.petersen@...cle.com,
        agross@...nel.org, linux-arm-msm@...r.kernel.org,
        linux-scsi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] ufs: ufs-qcom: Add support for DT-based gear and rate limiting

On Thu, 24 Jul 2025 at 10:35, Ram Kumar Dwivedi
<quic_rdwivedi@...cinc.com> wrote:
>
>
>
> On 23-Jul-25 12:24 AM, Dmitry Baryshkov wrote:
> > On Tue, Jul 22, 2025 at 09:41:01PM +0530, Ram Kumar Dwivedi wrote:
> >> Add optional device tree properties to limit Tx/Rx gear and rate during UFS
> >> initialization. Parse these properties in ufs_qcom_init() and apply them to
> >> host->host_params to enforce platform-specific constraints.
> >>
> >> Use this mechanism to cap the maximum gear or rate on platforms with
> >> hardware limitations, such as those required by some automotive customers
> >> using SA8155. Preserve the default behavior if the properties are not
> >> specified in the device tree.
> >>
> >> Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@...cinc.com>
> >> ---
> >>  drivers/ufs/host/ufs-qcom.c | 28 ++++++++++++++++++++++------
> >>  1 file changed, 22 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> >> index 4bbe4de1679b..5e7fd3257aca 100644
> >> --- a/drivers/ufs/host/ufs-qcom.c
> >> +++ b/drivers/ufs/host/ufs-qcom.c
> >> @@ -494,12 +494,8 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> >>       * If the HS-G5 PHY gear is used, update host_params->hs_rate to Rate-A,
> >>       * so that the subsequent power mode change shall stick to Rate-A.
> >>       */
> >> -    if (host->hw_ver.major == 0x5) {
> >> -            if (host->phy_gear == UFS_HS_G5)
> >> -                    host_params->hs_rate = PA_HS_MODE_A;
> >> -            else
> >> -                    host_params->hs_rate = PA_HS_MODE_B;
> >> -    }
> >> +    if (host->hw_ver.major == 0x5 && host->phy_gear == UFS_HS_G5)
> >> +            host_params->hs_rate = PA_HS_MODE_A;
> >
> > Why? This doesn't seem related.
>
> Hi Dmitry,
>
> I have refactored the patch to put this part in a separate patch in latest patchset.
>
> Thanks,
> Ram.
>
> >
> >>
> >>      mode = host_params->hs_rate == PA_HS_MODE_B ? PHY_MODE_UFS_HS_B : PHY_MODE_UFS_HS_A;
> >>
> >> @@ -1096,6 +1092,25 @@ static void ufs_qcom_set_phy_gear(struct ufs_qcom_host *host)
> >>      }
> >>  }
> >>
> >> +static void ufs_qcom_parse_limits(struct ufs_qcom_host *host)
> >> +{
> >> +    struct ufs_host_params *host_params = &host->host_params;
> >> +    struct device_node *np = host->hba->dev->of_node;
> >> +    u32 hs_gear, hs_rate = 0;
> >> +
> >> +    if (!np)
> >> +            return;
> >> +
> >> +    if (!of_property_read_u32(np, "limit-hs-gear", &hs_gear)) {
> >
> > These are generic properties, so they need to be handled in a generic
> > code path.
>
> Hi Dmitry,
>
>
> Below is the probe path for the UFS-QCOM platform driver:
>
> ufs_qcom_probe
>   └─ ufshcd_platform_init
>        └─ ufshcd_init
>             └─ ufs_qcom_init
>                  └─ ufs_qcom_set_host_params
>                       └─ ufshcd_init_host_params (initialized with default values)
>                            └─ ufs_qcom_get_hs_gear (overrides gear based on controller capability)
>                                 └─ ufs_qcom_set_phy_gear (further overrides based on controller limitations)
>
>
> The reason I added the logic in ufs-qcom.c is that even if it's placed in ufshcd-platform.c, the values get overridden in ufs-qcom.c.
> If you prefer, I can move the parsing logic API to ufshcd-platform.c but still it needs to be called from ufs-qcom.c.

I was thinking about ufshcd_init() or similar function.

>
> Thanks,
> Ram.
>
>
> >
> > Also, the patch with bindings should preceed driver and DT changes.
>
> Hi Dmitry,
>
> I have reordered the patch series to place the DT binding change as the first patch in latest patchset.
>
> Thanks,
> Ram.
>
>
> >
> >> +            host_params->hs_tx_gear = hs_gear;
> >> +            host_params->hs_rx_gear = hs_gear;
> >> +            host->phy_gear = hs_gear;
> >> +    }
> >> +
> >> +    if (!of_property_read_u32(np, "limit-rate", &hs_rate))
> >> +            host_params->hs_rate = hs_rate;
> >> +}
> >> +
> >>  static void ufs_qcom_set_host_params(struct ufs_hba *hba)
> >>  {
> >>      struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> >> @@ -1337,6 +1352,7 @@ static int ufs_qcom_init(struct ufs_hba *hba)
> >>      ufs_qcom_advertise_quirks(hba);
> >>      ufs_qcom_set_host_params(hba);
> >>      ufs_qcom_set_phy_gear(host);
> >> +    ufs_qcom_parse_limits(host);
> >>
> >>      err = ufs_qcom_ice_init(host);
> >>      if (err)
> >> --
> >> 2.50.1
> >>
> >
>


-- 
With best wishes
Dmitry