Re: [PATCH v4 4/4] firmware: arm_scmi: Add qcom hvc/shmem transport support
From: Nikunj Kela
Date: Wed Oct 04 2023 - 13:49:41 EST
On 10/4/2023 9:06 AM, Sudeep Holla wrote:
On Tue, Oct 03, 2023 at 09:16:27AM -0700, Nikunj Kela wrote:
On 10/3/2023 4:19 AM, Sudeep Holla wrote:
On Mon, Sep 11, 2023 at 12:43:59PM -0700, Nikunj Kela wrote:
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@xxxxxxxxxxx>
---
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;
Can it be unsigned long instead so that it just works for both 32 and 64 bit.
My first version of this patch was ulong but Bjorn suggested to make this
structure size fixed i.e. architecture independent. Hence changed it to u64.
If you are ok with ulong, I can change it back to ulong.
SMCCC pre-v1.2 used the common structure in that way. I don't see any issue
with that. I haven't followed Bjorn suggestions/comments though.
Ok.
+ bool qcom_xport;
Do we really need this ?
Not if we initialize it with a negative value since 0 is a valid value for
cap-id.
Fine with negative value(-EINVAL may be).
Ok.
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);
So unlike 'arm,scmi-smc', you don't want 'arm,smc-id' in the DT ? Any
particular reason ? Just to get both FID and cap ID from shmem ?
I am fine either way. If you use from DT(via arm,smc-id), then "qcom,scmi"
can be just addition compatible that expects you to read cap-id from the
shmem. May need adjustment in the binding as you allow both
"qcom,scmi-smc", "arm,scmi-smc". I will leave the details to you.
Ok.
I could use smc-id binding for func-id, it's just two parameters will come
from two different places so thought of keeping everything at one place to
maintain consistency. Since DT can't take cap-id, I decided to move
func-id. I am fine if you want me to use smc-id binding.
Up to you. If you want to make "qcom,scmi-smc" and "arm,scmi-smc"
compatible in way in that way or you can keep it incompatible as you have
proposed in this patch set.
Ok.
+#ifdef CONFIG_ARM64
I would rather make this arch agnostic using CONFIG_64BIT
ok.
+ cap_id = readq((void __iomem *)(scmi_info->shmem) + size - 8);
Do you need __iomem typecast here ? Is scmi_info->shmem not already __iomem ?
Also scmi_info->shmem is ioremapped just few steps above and you are using
read* here, is that safe ?
I saw some compilation warnings without __iomem. I will use ioread* API
instead of read*.
That was the clue that you were using __iomem with read* calls IMO.
Ok.
+#else
+ /* capability-id is 32 bit wide on 32bit machines */
+ cap_id = rieadl((void __iomem *)(scmi_info->shmem) + size - 8);
Other thought once you move for u64 to unsigned long you need not have
#ifdeffery, just do copy of sizeof(unsigned long)
Right, my first version was like that only.
OK
+#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)
Just make sure cap_id is set only for qcom and just use that as your flag.
No point in setting always true scmi_info->qcom_xport and using it here.
ok, I can remove that. Though 0 is a valid value for cap-id so will have to
init cap-id with a negative value.
Yes as mentioned above.
Ok.