[PATCH v5 2/2] firmware: arm_scmi: Add qcom smc/hvc transport support

Nikunj Kela
2023-10-06T16:43:22Z

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 smc/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 SMC/HVC call is invoked.

The capability-id is allocated by the hypervisor on bootup and is 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 | 33 ++++++++++++++++++++++++++++--
2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 87383c05424b..09371f40d61f 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-smc", .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 c193516a254d..3d594d65ab14 100644
--- a/drivers/firmware/arm_scmi/smc.c
+++ b/drivers/firmware/arm_scmi/smc.c
@@ -50,6 +50,8 @@
* @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: smc/hvc doorbell's capability id to be used on Qualcomm virtual
+ * platforms
*/

struct scmi_smc {
@@ -63,6 +65,7 @@ struct scmi_smc {
u32 func_id;
u32 param_page;
u32 param_offset;
+ s64 cap_id;
};

static irqreturn_t smc_msg_done_isr(int irq, void *data)
@@ -128,6 +131,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
resource_size_t size;
struct resource res;
struct device_node *np;
+ s64 cap_id = -EINVAL;
u32 func_id;
int ret;

@@ -162,6 +166,25 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
if (ret < 0)
return ret;

+ if (of_device_is_compatible(dev->of_node, "qcom,scmi-smc")) {
+ /* The capability-id is kept in last 8 bytes of shmem.
+ * +-------+
+ * | |
+ * | shmem |
+ * | |
+ * | |
+ * +-------+ <-- (size - 8)
+ * | capId |
+ * +-------+ <-- size
+ */
+
+#ifdef CONFIG_64BIT
+ cap_id = ioread64((void *)scmi_info->shmem + size - 8);
+#else
+ cap_id = ioread32((void *)scmi_info->shmem + size - 8);
+#endif
+ }
+
if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param")) {
scmi_info->param_page = SHMEM_PAGE(res.start);
scmi_info->param_offset = SHMEM_OFFSET(res.start);
@@ -184,6 +207,7 @@ 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 +237,7 @@ 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;
+ long cap_id = (long)scmi_info->cap_id;

/*
* Channel will be released only once response has been
@@ -222,8 +247,12 @@ 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 (cap_id >= 0)
+ arm_smccc_1_1_invoke(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