Re: [PATCH RFT v2 09/14] clk: qcom: smd-rpm: Add support for keepalive votes

Dmitry Baryshkov
2023-03-09T00:54:58Z

On 08/03/2023 23:35, Konrad Dybcio wrote:
> Some bus clock should always have a minimum (19.2 MHz) vote cast on
> them, otherwise the platform will fall apart, hang and reboot.
>
> Add support for specifying which clocks should be kept alive and
> always keep a vote on XO_A to make sure the clock tree doesn't
> collapse. This removes the need to keep a maximum vote that was
> previously guaranteed by clk_smd_rpm_handoff.
>
> This commit is a combination of existing (not-exactly-upstream) work
> by Taniya Das, Shawn Guo and myself.
>
> Co-developed-by: Shawn Guo <shawn.guo@linaro.org>
> Co-developed-by: Taniya Das <quic_tdas@quicinc.com>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
> ---
> drivers/clk/qcom/clk-smd-rpm.c | 29 +++++++++++++++++++++++++++--
> 1 file changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
> index eb7781e5c8c1..d89918f9ae60 100644
> --- a/drivers/clk/qcom/clk-smd-rpm.c
> +++ b/drivers/clk/qcom/clk-smd-rpm.c
> @@ -45,15 +45,17 @@
> }, \
> }; \
> __DEFINE_CLK_SMD_RPM_AO_PREFIX(_prefix, _name, _active, type, \
> - r_id, key, ao_flags)
> + r_id, key, ao_flags, false)
>
> #define __DEFINE_CLK_SMD_RPM_AO_PREFIX(_prefix, _name, _active, \
> - type, r_id, key, ao_flags) \
> + type, r_id, key, ao_flags, \
> + _keep_alive) \
> static struct clk_smd_rpm clk_smd_rpm_##_prefix##_active = { \
> .rpm_res_type = (type), \
> .rpm_clk_id = (r_id), \
> .active_only = true, \
> .rpm_key = (key), \
> + .keep_alive = (_keep_alive), \
> .peer = &clk_smd_rpm_##_prefix##_name, \
> .rate = INT_MAX, \
> .hw.init = &(struct clk_init_data){ \
> @@ -170,6 +172,7 @@ struct clk_smd_rpm {
> const bool active_only;
> bool enabled;
> bool branch;
> + bool keep_alive;
> struct clk_smd_rpm *peer;
> struct clk_hw hw;
> unsigned long rate;
> @@ -198,11 +201,16 @@ static int clk_smd_rpm_handoff(struct clk_smd_rpm *r)
> .value = cpu_to_le32(r->branch ? 1 : INT_MAX),
> };
>
> + /* Set up keepalive clocks with a minimum bus rate */
> + if (r->keep_alive)
> + req.value = cpu_to_le32(19200); /* 19.2 MHz */

Should this be set to cpu_to_le32(max(19200, ...)) ?

> +
> ret = qcom_rpm_smd_write(r->rpm, QCOM_SMD_RPM_ACTIVE_STATE,
> r->rpm_res_type, r->rpm_clk_id, &req,
> sizeof(req));
> if (ret)
> return ret;
> +
> ret = qcom_rpm_smd_write(r->rpm, QCOM_SMD_RPM_SLEEP_STATE,
> r->rpm_res_type, r->rpm_clk_id, &req,
> sizeof(req));
> @@ -438,12 +446,29 @@ static int clk_smd_rpm_is_enabled(struct clk_hw *hw)
> return r->enabled;
> }
>
> +static int clk_smd_rpm_determine_rate(struct clk_hw *hw,
> + struct clk_rate_request *req)
> +{
> + struct clk_smd_rpm *r = to_clk_smd_rpm(hw);
> +
> + /*
> + * RPM resolves the rates internally. All we have to do on the kernel
> + * side is ensure that we don't accidentally put down the keepalive
> + * clocks, which could happen if they received a vote below 19.2 MHz.
> + */
> + if (r->keep_alive)
> + req->rate = max(req->rate, 19200000UL);
> +
> + return 0;
> +}
> +
> static const struct clk_ops clk_smd_rpm_ops = {
> .prepare = clk_smd_rpm_prepare,
> .unprepare = clk_smd_rpm_unprepare,
> .set_rate = clk_smd_rpm_set_rate,
> .round_rate = clk_smd_rpm_round_rate,
> .recalc_rate = clk_smd_rpm_recalc_rate,
> + .determine_rate = clk_smd_rpm_determine_rate,
> .is_enabled = clk_smd_rpm_is_enabled,
> .is_prepared = clk_smd_rpm_is_enabled,
> };
>

--
With best wishes
Dmitry