Re: [PATCH v10 4/6] arm64: dts: qcom: sm8450: Add OPP table support to PCIe

From: Krishna Chaitanya Chundru
Date: Mon Apr 22 2024 - 12:55:41 EST




On 4/22/2024 8:14 PM, Manivannan Sadhasivam wrote:
On Tue, Apr 09, 2024 at 03:43:22PM +0530, Krishna chaitanya chundru wrote:
PCIe needs to choose the appropriate performance state of RPMh power

'PCIe host controller driver'

domain and interconnect bandwidth based up on the PCIe data rate.

'based on the PCIe data rate'


Add the OPP table support to specify RPMh performance states and

'Hence, add...'

interconnect peak bandwidth.

Different link configurations may share the same aggregate bandwidth,

'It should be noted that the different...'

e.g., a 2.5 GT/s x2 link and a 5.0 GT/s x1 link have the same bandwidth
and share the same OPP entry.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
---
arch/arm64/boot/dts/qcom/sm8450.dtsi | 77 ++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
index 615296e13c43..9dfe16012726 100644
--- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
+++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
@@ -1855,7 +1855,35 @@ &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
pinctrl-names = "default";
pinctrl-0 = <&pcie0_default_state>;
+ operating-points-v2 = <&pcie0_opp_table>;
+
status = "disabled";
+
+ pcie0_opp_table: opp-table {
+ compatible = "operating-points-v2";
+
+ /* GEN 1 x1 */
+ opp-2500000 {
+ opp-hz = /bits/ 64 <2500000>;
+ required-opps = <&rpmhpd_opp_low_svs>;
+ opp-peak-kBps = <250000 1>;
+ };
+
+ /* GEN 2 x1 */
+ opp-5000000 {
+ opp-hz = /bits/ 64 <5000000>;
+ required-opps = <&rpmhpd_opp_low_svs>;
+ opp-peak-kBps = <500000 1>;
+ };
+
+ /* GEN 3 x1 */
+ opp-8000000 {
+ opp-hz = /bits/ 64 <8000000>;

I doubt this value. See below...

+ required-opps = <&rpmhpd_opp_nom>;
+ opp-peak-kBps = <984500 1>;
+ };
+ };
+
};
pcie0_phy: phy@1c06000 {
@@ -1982,7 +2010,56 @@ &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
pinctrl-names = "default";
pinctrl-0 = <&pcie1_default_state>;
+ operating-points-v2 = <&pcie1_opp_table>;
+
status = "disabled";
+
+ pcie1_opp_table: opp-table {
+ compatible = "operating-points-v2";
+
+ /* GEN 1 x1 */
+ opp-2500000 {
+ opp-hz = /bits/ 64 <2500000>;
+ required-opps = <&rpmhpd_opp_low_svs>;
+ opp-peak-kBps = <250000 1>;
+ };
+
+ /* GEN 1 x2 GEN 2 x1 */
+ opp-5000000 {
+ opp-hz = /bits/ 64 <5000000>;
+ required-opps = <&rpmhpd_opp_low_svs>;
+ opp-peak-kBps = <500000 1>;
+ };
+
+ /* GEN 2 x2 */
+ opp-10000000 {
+ opp-hz = /bits/ 64 <10000000>;
+ required-opps = <&rpmhpd_opp_low_svs>;
+ opp-peak-kBps = <1000000 1>;
+ };
+
+ /* GEN 3 x1 */
+ opp-8000000 {
+ opp-hz = /bits/ 64 <8000000>;

GEN 3 x1 frequency is lower than GEN 2 x2? This looks strange. Both should be of
same frequency.

Gen2 is 5GT/s where as GEN3 is 8GT/s. so the freq for 3 x1(8 x1 GT/s) is
less than Gen2 x2(5 x2 GT/s)

- Krishna Chaitanya.
+ required-opps = <&rpmhpd_opp_nom>;
+ opp-peak-kBps = <984500 1>;
+ };
+
+ /* GEN 3 x2 GEN 4 x1 */

'GEN 3 x2 and GEN 4 x1'

- Mani