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

Ram Kumar Dwivedi
2025-07-24T07:36:00Z

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@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.

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.

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
>>
>