Re: [PATCH V2] scsi: ufs: ufs-qcom: Enable only lane clocks in lane clock APIs

[Manivannan Sadhasivam]

On Wed, Sep 09, 2026 at 11:09:44AM +0530, Nitin Rawat wrote:
> ufs_qcom_enable_lane_clks() and ufs_qcom_disable_lane_clks() currently
> use clk_bulk_prepare_enable()/clk_bulk_disable_unprepare() on the
> entire host->clks array obtained from devm_clk_bulk_get_all(). This
> array contains all device clocks, not just lane symbol clocks.
> 
> Since the UFS core framework already manages the non-lane clocks via
> the setup_clocks callback, the bulk enable/disable in the lane clock
> APIs resulted in duplicate reference count increments on those shared
> clocks. The extra enable counts were never balanced by a corresponding
> disable from the framework's clock gating path, preventing the clock
> reference counts from reaching zero and ultimately blocking CXO
> shutdown during low-power states.
> 
> Fix this by restricting the lane clock APIs to only prepare/enable
> and disable/unprepare the three lane symbol clocks (tx_lane0_sync_clk,
> rx_lane0_sync_clk, rx_lane1_sync_clk), leaving the handling of all
> other clocks to the UFS core framework. The lane clocks are now
> acquired individually via devm_clk_get() instead of being looked up
> in the bulk clock array.
> 
> Signed-off-by: Nitin Rawat <nitin.rawat@xxxxxxxxxxxxxxxx>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>

One comment below for future optimization.

> ---
> Changes from v1:
> 1. As per konrad's comment, used devm_clk_get instead of to get
>    lane clock handle instead of using bulk call API.
> ---
>  drivers/ufs/host/ufs-qcom.c | 47 ++++++++++++++++++++++++++++++-------
>  drivers/ufs/host/ufs-qcom.h |  5 ++--
>  2 files changed, 42 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index aa2ac2cd2b69..50f34d1c5fdb 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -348,7 +348,9 @@ static void ufs_qcom_disable_lane_clks(struct ufs_qcom_host *host)
>  	if (!host->is_lane_clks_enabled)
>  		return;
> 
> -	clk_bulk_disable_unprepare(host->num_clks, host->clks);
> +	clk_disable_unprepare(host->rx_lane1_sync_clk);
> +	clk_disable_unprepare(host->rx_lane0_sync_clk);
> +	clk_disable_unprepare(host->tx_lane0_sync_clk);
> 
>  	host->is_lane_clks_enabled = false;
>  }
> @@ -357,28 +359,57 @@ static int ufs_qcom_enable_lane_clks(struct ufs_qcom_host *host)
>  {
>  	int err;
> 
> -	err = clk_bulk_prepare_enable(host->num_clks, host->clks);
> +	if (host->is_lane_clks_enabled)
> +		return 0;

Presence of this check/flag gives an indication that lane_clocks are not
handled in a refcounted manner i.e., ufs_qcom_{enable/disabled}_lane_clks() are
called multiple times from different places and the code only ensures that these
are called only once. As a future optimization, I would recommend removing this
check and ensure that enable/disable are called in a refcounted manner. Since
the clk framework handles refcount, the UFS driver's job is simply to ensure
the enable/disable count matches to avoid under/over flows.

- Mani

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