Re: [Patch v5 6/8] firmware: qcom: scm: Add support for ARM64 SoCs

On Thu, Jun 02, 2016 at 03:28:40PM -0700, Stephen Boyd wrote:

On 05/12, Andy Gross wrote:

quoted

+
+#define MAX_QCOM_SCM_ARGS 10
+#define MAX_QCOM_SCM_RETS 3
+
+#define QCOM_SCM_ARGS_IMPL(num, a, b, c, d, e, f, g, h, i, j, ...) (\
+			   (((a) & 0x3) << 4) | \
+			   (((b) & 0x3) << 6) | \
+			   (((c) & 0x3) << 8) | \
+			   (((d) & 0x3) << 10) | \
+			   (((e) & 0x3) << 12) | \
+			   (((f) & 0x3) << 14) | \
+			   (((g) & 0x3) << 16) | \
+			   (((h) & 0x3) << 18) | \
+			   (((i) & 0x3) << 20) | \
+			   (((j) & 0x3) << 22) | \
+			   (num & 0xf))

Parenthesis around num?

To be more precise, yes.

quoted

+
+#define QCOM_SCM_ARGS(...) QCOM_SCM_ARGS_IMPL(__VA_ARGS__, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
+
+/**
+ * struct qcom_scm_desc
+ * @arginfo:	Metadata describing the arguments in args[]
+ * @args:	The array of arguments for the secure syscall
+ * @res:	The values returned by the secure syscall
+ */
+struct qcom_scm_desc {
+	u32 arginfo;
+	u64 args[MAX_QCOM_SCM_ARGS];
+	struct arm_smccc_res res;
+};

If we split the res from the descriptor structure we could make
the qcom_scm_desc const in qcom_scm_call(). We would have to add
another argument to the function though, not sure if this is a
big win idea, but just an idea to keep things "safer".

I like that idea.  The arginfo and args are immutable so this really locks down
the interface.  I'll try it out and see how it turns out.

quoted

+
+static u64 qcom_smccc_convention = -1;
+static DEFINE_MUTEX(qcom_scm_lock);
+
+#define QCOM_SCM_EBUSY_WAIT_MS 30
+#define QCOM_SCM_EBUSY_MAX_RETRY 20
+
+#define N_EXT_QCOM_SCM_ARGS 7
+#define FIRST_EXT_ARG_IDX 3
+#define N_REGISTER_ARGS (MAX_QCOM_SCM_ARGS - N_EXT_QCOM_SCM_ARGS + 1)
+
+/**
+ * qcom_scm_call() - Invoke a syscall in the secure world
+ * @dev:	device
+ * @svc_id:	service identifier
+ * @cmd_id:	command identifier
+ * @desc:	Descriptor structure containing arguments and return values
+ *
+ * Sends a command to the SCM and waits for the command to finish processing.
+ * This should *only* be called in pre-emptible context.
+*/
+static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
+			 struct qcom_scm_desc *desc)
+{
+	int arglen = desc->arginfo & 0xf;
+	int retry_count = 0, i;
+	u32 fn_id = QCOM_SCM_FNID(svc_id, cmd_id);
+	u64 cmd, x5 = desc->args[FIRST_EXT_ARG_IDX];
+	dma_addr_t args_phys = 0;
+	void *args_virt = NULL;
+	size_t alloc_len;
+
+	if (unlikely(arglen > N_REGISTER_ARGS)) {
+		alloc_len = N_EXT_QCOM_SCM_ARGS * sizeof(u64);
+		args_virt = kzalloc(PAGE_ALIGN(alloc_len), GFP_KERNEL);
+
+		if (!args_virt)
+			return qcom_scm_remap_error(-ENOMEM);

Just return -ENOMEM here?

Ok.  That would make it easier to follow.

quoted

+
+		if (qcom_smccc_convention == ARM_SMCCC_SMC_32) {
+			__le32 *args = args_virt;
+
+			for (i = 0; i < N_EXT_QCOM_SCM_ARGS; i++)
+				args[i] = cpu_to_le32(desc->args[i +
+						      FIRST_EXT_ARG_IDX]);
+		} else {
+			__le64 *args = args_virt;
+
+			for (i = 0; i < N_EXT_QCOM_SCM_ARGS; i++)
+				args[i] = cpu_to_le64(desc->args[i +
+						      FIRST_EXT_ARG_IDX]);
+		}
+
+		args_phys = dma_map_single(dev, args_virt, alloc_len,
+					   DMA_TO_DEVICE);
+
+		if (dma_mapping_error(dev, args_phys)) {
+			kfree(args_virt);
+			return qcom_scm_remap_error(-ENOMEM);

Just return -ENOMEM here?

Ok.  That would make it easier to follow.