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

Dmitry Baryshkov
2025-07-22T18:54:24Z

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@quicinc.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.

>
> 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.

Also, the patch with bindings should preceed driver and DT changes.

> + 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