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

Sudeep Holla
2023-10-03T11:19:20Z

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@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;

Can it be unsigned long instead so that it just works for both 32 and 64 bit.

> + bool qcom_xport;

Do we really need this ?

> };
>
> 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;

Ditto..

> 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 ?

> +#ifdef CONFIG_ARM64

I would rather make this arch agnostic using CONFIG_64BIT

> + 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 ?

> +#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)

> +#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.

> + 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
>

--
Regards,
Sudeep