clk: qcom: smd-rpm: Make BI_TCXO_AO critical

We should never let go of the active-only XO vote, as otherwise the
RPM may decide that there are no online users and it can be shut down,
resulting in a total, uncontrolled system collapse.

Guarantee this through adding the CLK_IS_CRITICAL flag.
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Tested-by: Matti Lehtimäki <matti.lehtimaki@gmail.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230501-topic-rpmcc_xo_a-v1-3-93f18e47b607@linaro.org

drivers/clk/qcom/clk-smd-rpm.c

@@ -440,7 +440,8 @@ static const struct clk_ops clk_smd_rpm_branch_ops = {
 	.recalc_rate	= clk_smd_rpm_recalc_rate,
 };
 
-DEFINE_CLK_SMD_RPM_BRANCH_A(bi_tcxo, QCOM_SMD_RPM_MISC_CLK, 0, 19200000, 0);
+/* Disabling BI_TCXO_AO could gate the root clock source of the entire system. */
+DEFINE_CLK_SMD_RPM_BRANCH_A(bi_tcxo, QCOM_SMD_RPM_MISC_CLK, 0, 19200000, CLK_IS_CRITICAL);
 DEFINE_CLK_SMD_RPM_BRANCH(qdss, QCOM_SMD_RPM_MISC_CLK, 1, 19200000);
 DEFINE_CLK_SMD_RPM_QDSS(qdss, QCOM_SMD_RPM_MISC_CLK, 1);
 DEFINE_CLK_SMD_RPM_BRANCH_A(bimc_freq_log, QCOM_SMD_RPM_MISC_CLK, 4, 1, 0);