[PATCH v4 4/4] firmware: arm_scmi: Add qcom hvc/shmem transport support

Nikunj Kela
2023-09-11T20:50:27Z

This change adds the support for SCMI message exchange on Qualcomm
virtual platforms.

The hypervisor associates an object-id also known as capability-id
with each hvc doorbell object. The capability-id is used to identify the
doorbell from the VM's capability namespace, similar to a file-descriptor.

The hypervisor, in addition to the function-id, expects the capability-id
to be passed in x1 register when HVC call is invoked.

The function-id & capability-id are allocated by the hypervisor on bootup
and are stored in the shmem region by the firmware before starting Linux.

Signed-off-by: Nikunj Kela <quic_nkela@quicinc.com>
---
drivers/firmware/arm_scmi/driver.c | 1 +
drivers/firmware/arm_scmi/smc.c | 47 ++++++++++++++++++++++++++----
2 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 87383c05424b..ea344bc6ae49 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -2915,6 +2915,7 @@ static const struct of_device_id scmi_of_match[] = {
#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
{ .compatible = "arm,scmi-smc-param", .data = &scmi_smc_desc},
+ { .compatible = "qcom,scmi-hvc-shmem", .data = &scmi_smc_desc},
#endif
#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
{ .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
index 0a0b7e401159..94ec07fdc14a 100644
--- a/drivers/firmware/arm_scmi/smc.c
+++ b/drivers/firmware/arm_scmi/smc.c
@@ -50,6 +50,9 @@
* @func_id: smc/hvc call function id
* @param_page: 4K page number of the shmem channel
* @param_offset: Offset within the 4K page of the shmem channel
+ * @cap_id: hvc doorbell's capability id to be used on Qualcomm virtual
+ * platforms
+ * @qcom_xport: Flag to indicate the transport on Qualcomm virtual platforms
*/

struct scmi_smc {
@@ -63,6 +66,8 @@ struct scmi_smc {
u32 func_id;
u32 param_page;
u32 param_offset;
+ u64 cap_id;
+ bool qcom_xport;
};

static irqreturn_t smc_msg_done_isr(int irq, void *data)
@@ -129,6 +134,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
struct resource res;
struct device_node *np;
u32 func_id;
+ u64 cap_id;
int ret;

if (!tx)
@@ -158,9 +164,34 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
return -EADDRNOTAVAIL;
}

- ret = of_property_read_u32(dev->of_node, "arm,smc-id", &func_id);
- if (ret < 0)
- return ret;
+ if (of_device_is_compatible(dev->of_node, "qcom,scmi-hvc-shmem")) {
+ scmi_info->qcom_xport = true;
+
+ /* The func-id & capability-id are kept in last 16 bytes of shmem.
+ * +-------+
+ * | |
+ * | shmem |
+ * | |
+ * | |
+ * +-------+ <-- (size - 16)
+ * | funcId|
+ * +-------+ <-- (size - 8)
+ * | capId |
+ * +-------+ <-- size
+ */
+
+ func_id = readl((void __iomem *)(scmi_info->shmem) + size - 16);
+#ifdef CONFIG_ARM64
+ cap_id = readq((void __iomem *)(scmi_info->shmem) + size - 8);
+#else
+ /* capability-id is 32 bit wide on 32bit machines */
+ cap_id = readl((void __iomem *)(scmi_info->shmem) + size - 8);
+#endif
+ } else {
+ ret = of_property_read_u32(dev->of_node, "arm,smc-id", &func_id);
+ if (ret < 0)
+ return ret;
+ }

if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param")) {
scmi_info->param_page = SHMEM_PAGE(res.start);
@@ -184,6 +215,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
}

scmi_info->func_id = func_id;
+ scmi_info->cap_id = cap_id;
scmi_info->cinfo = cinfo;
smc_channel_lock_init(scmi_info);
cinfo->transport_info = scmi_info;
@@ -213,6 +245,7 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
struct arm_smccc_res res;
unsigned long page = scmi_info->param_page;
unsigned long offset = scmi_info->param_offset;
+ unsigned long cap_id = (unsigned long)scmi_info->cap_id;

/*
* Channel will be released only once response has been
@@ -222,8 +255,12 @@ static int smc_send_message(struct scmi_chan_info *cinfo,

shmem_tx_prepare(scmi_info->shmem, xfer, cinfo);

- arm_smccc_1_1_invoke(scmi_info->func_id, page, offset, 0, 0, 0, 0, 0,
- &res);
+ if (scmi_info->qcom_xport)
+ arm_smccc_1_1_hvc(scmi_info->func_id, cap_id, 0, 0, 0, 0, 0, 0,
+ &res);
+ else
+ arm_smccc_1_1_invoke(scmi_info->func_id, page, offset, 0, 0, 0,
+ 0, 0, &res);

/* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
if (res.a0) {
--
2.17.1