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From:   Douglas Anderson <dianders@chromium.org>
To:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Maulik Shah <mkshah@codeaurora.org>
Cc:     mka@chromium.org, Rajendra Nayak <rnayak@codeaurora.org>,
        evgreen@chromium.org, Lina Iyer <ilina@codeaurora.org>,
        swboyd@chromium.org, Douglas Anderson <dianders@chromium.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [RFT PATCH v2 06/10] drivers: qcom: rpmh-rsc: Comment tcs_is_free() + warn if state mismatch
Date:   Wed, 11 Mar 2020 16:13:44 -0700
Message-Id: <20200311161104.RFT.v2.6.Icf2213131ea652087f100129359052c83601f8b0@changeid>
In-Reply-To: <20200311231348.129254-1-dianders@chromium.org>
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tcs_is_free() had two checks in it: does the software think that the
TCS is free and does the hardware think that the TCS is free.  Let's
comment this and also add a warning in the case that software and
hardware disagree, at least for ACTIVE_ONLY TCS.

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

Changes in v2:
- Comment tcs_is_free() new for v2; replaces old patch 6.

 drivers/soc/qcom/rpmh-rsc.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index 9d2669cbd994..93f5d1fb71ca 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -181,8 +181,27 @@ 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 software thinks it's in use then it's definitely in use */
+	if (test_bit(tcs_id, drv->tcs_in_use))
+		return false;
+
+	/* If hardware agrees it's free then it's definitely free */
+	if (read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id) != 0)
+		return true;
+
+	/*
+	 * If we're here then software and hardware disagree about whether
+	 * the TCS is free.  Software thinks it is free and hardware thinks
+	 * it is not.
+	 *
+	 * Maybe this should be a warning in all cases, but it's almost
+	 * certainly a warning for the ACTIVE_TCS where nobody else should
+	 * be doing anything else behind our backs.  For now we'll just
+	 * warn there and then still return that we're in use.
+	 */
+	WARN(drv->tcs[tcs_id].type == ACTIVE_TCS,
+	     "Driver thought TCS was free but HW reported busy\n");
+	return false;
 }
 
 /**
-- 
2.25.1.481.gfbce0eb801-goog