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Subject[RFT PATCH v2 02/10] drivers: qcom: rpmh-rsc: Document the register layout better
Date
Perhaps it's just me, it took a really long time to understand what
the register layout of rpmh-rsc was just from the #defines. Let's add
a bunch of comments describing which blocks are part of other blocks.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v2:
- Now prose in comments instead of struct definitions.
- Pretty ASCII art from Stephen.

drivers/soc/qcom/rpmh-rsc.c | 78 ++++++++++++++++++++++++++++++++++---
1 file changed, 73 insertions(+), 5 deletions(-)

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index b87b79f0347d..02c8e0ffbbe4 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -37,14 +37,24 @@
#define DRV_NCPT_MASK 0x1F
#define DRV_NCPT_SHIFT 27

-/* Register offsets */
+/*
+ * Register offsets within a TCS.
+ *
+ * TCSs are stored one after another; multiply tcs_id by RSC_DRV_TCS_OFFSET
+ * to find a given TCS and add one of the below to find a register.
+ */
#define RSC_DRV_IRQ_ENABLE 0x00
#define RSC_DRV_IRQ_STATUS 0x04
-#define RSC_DRV_IRQ_CLEAR 0x08
-#define RSC_DRV_CMD_WAIT_FOR_CMPL 0x10
+#define RSC_DRV_IRQ_CLEAR 0x08 /* w/o; write 1 to clear */
+#define RSC_DRV_CMD_WAIT_FOR_CMPL 0x10 /* 1 bit per command */
#define RSC_DRV_CONTROL 0x14
-#define RSC_DRV_STATUS 0x18
-#define RSC_DRV_CMD_ENABLE 0x1C
+#define RSC_DRV_STATUS 0x18 /* zero if tcs is busy */
+#define RSC_DRV_CMD_ENABLE 0x1C /* 1 bit per command */
+
+/*
+ * Commands (up to 16) start at 0x30 in a TCS; multiply command index
+ * by RSC_DRV_CMD_OFFSET and add one of the below to find a register.
+ */
#define RSC_DRV_CMD_MSGID 0x30
#define RSC_DRV_CMD_ADDR 0x34
#define RSC_DRV_CMD_DATA 0x38
@@ -61,6 +71,64 @@
#define CMD_STATUS_ISSUED BIT(8)
#define CMD_STATUS_COMPL BIT(16)

+/*
+ * Here's a high level overview of how all the registers in RPMH work
+ * together:
+ *
+ * - The main rpmh-rsc address is the base of a register space that can
+ * be used to find overall configuration of the hardware
+ * (DRV_PRNT_CHLD_CONFIG). Also found within the rpmh-rsc register
+ * space are all the TCS blocks. The offset of the TCS blocks is
+ * specified in the device tree by "qcom,tcs-offset" and used to
+ * compute tcs_base.
+ * - TCS blocks come one after another. Type, count, and order are
+ * specified by the device tree as "qcom,tcs-config".
+ * - Each TCS block has some registers, then space for up to 16 commands.
+ * Note that though address space is reserved for 16 commands, fewer
+ * might be present. See ncpt (num cmds per TCS).
+ * - The first TCS block is special in that it has registers to control
+ * interrupts (RSC_DRV_IRQ_XXX). Space for these registers is reserved
+ * in all TCS blocks to make the math easier, but only the first one
+ * matters.
+ *
+ * Here's a picture:
+ *
+ * +---------------------------------------------------+
+ * |RSC |
+ * | ctrl |
+ * | |
+ * | Drvs: |
+ * | +-----------------------------------------------+ |
+ * | |DRV0 | |
+ * | | ctrl | |
+ * | | | |
+ * | | TCSs: | |
+ * | | +------------------------------------------+ | |
+ * | | |TCS0 | | | | | | | | | | | | | | |
+ * | | | IRQ | 0| 1| 2| 3| 4| 5| .| .| .| .|14|15| | |
+ * | | | ctrl | | | | | | | | | | | | | | |
+ * | | +------------------------------------------+ | |
+ * | | +------------------------------------------+ | |
+ * | | |TCS1 | | | | | | | | | | | | | | |
+ * | | | | 0| 1| 2| 3| 4| 5| .| .| .| .|14|15| | |
+ * | | | ctrl | | | | | | | | | | | | | | |
+ * | | +------------------------------------------+ | |
+ * | | +------------------------------------------+ | |
+ * | | |TCS2 | | | | | | | | | | | | | | |
+ * | | | | 0| 1| 2| 3| 4| 5| .| .| .| .|14|15| | |
+ * | | | ctrl | | | | | | | | | | | | | | |
+ * | | +------------------------------------------+ | |
+ * | | ...... | |
+ * | +-----------------------------------------------+ |
+ * | +-----------------------------------------------+ |
+ * | |DRV1 | |
+ * | | (same as DRV0) | |
+ * | +-----------------------------------------------+ |
+ * | ...... |
+ * +---------------------------------------------------+
+ */
+
+
static u32 read_tcs_cmd(struct rsc_drv *drv, int reg, int tcs_id, int cmd_id)
{
return readl_relaxed(drv->tcs_base + RSC_DRV_TCS_OFFSET * tcs_id + reg +
--
2.25.1.481.gfbce0eb801-goog
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