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Subject[RFT PATCH 6/9] drivers: qcom: rpmh-rsc: Only use "tcs_in_use" for ACTIVE_ONLY
Date
From trawling through the code (see the "A lot of comments" change) I
found that "tcs_in_use" was only kept up-to-date for ACTIVE_ONLY TCSs.
...yet tcs_is_free() was checking the variable called from
tcs_invalidate() and tcs_invalidate() is only used for non-ACTIVE_ONLY
TCSs.

Let's change tcs_invalidate() to just check the "RSC_DRV_STATUS"
register, which was presumably the important part.

It also feels like for ACTIVE_ONLY TCSs that it probably wasn't
important to check the "RSC_DRV_STATUS". We'll keep doing it just in
case but we'll add a warning if it ever actually mattered.

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

drivers/soc/qcom/rpmh-rsc.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index 190226151029..c63441182358 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -164,7 +164,7 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
}

/**
- * tcs_is_free() - Return if a TCS is totally free.
+ * tcs_is_free() - Return if an ACTIVE_ONLY TCS is totally free.
* @drv: The RSC controller.
* @tcs_id: The global ID of this TCS.
*
@@ -177,8 +177,23 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
*/
static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
{
- return !test_bit(tcs_id, drv->tcs_in_use) &&
- read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id);
+ if (test_bit(tcs_id, drv->tcs_in_use))
+ return false;
+
+ if (read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id) != 0)
+ return true;
+
+ /*
+ * If this warning never ever hits then we can change this function
+ * to just look at "tcs_in_use" and skip the read of the
+ * RSC_DRV_STATUS register.
+ *
+ * If this warning _does_ hit, we should figure out if this is just
+ * the way the hardware works or if there is some bug being pointed
+ * out.
+ */
+ WARN(1, "Driver thought TCS was free but HW reported busy\n");
+ return false;
}

/**
@@ -204,7 +219,7 @@ static int tcs_invalidate(struct rsc_drv *drv, int type)
}

for (m = tcs->offset; m < tcs->offset + tcs->num_tcs; m++) {
- if (!tcs_is_free(drv, m)) {
+ if (read_tcs_reg(drv, RSC_DRV_STATUS, m) == 0) {
spin_unlock(&tcs->lock);
return -EAGAIN;
}
--
2.25.1.481.gfbce0eb801-goog
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