linux-kernel - [PATCH net-next 3/4] net: ipa: use Qtime for IPA v4.5 aggregation time limit

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Message-Id: <20201130233712.29113-4-elder@linaro.org>
Date:   Mon, 30 Nov 2020 17:37:11 -0600
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     evgreen@...omium.org, subashab@...eaurora.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 3/4] net: ipa: use Qtime for IPA v4.5 aggregation time limit

Change aggr_time_limit_encoded() to properly calculate the
aggregation time limit to use for IPA v4.5.

Older IPA versions program the AGGR_GRANULARITY field of the
of the COUNTER_CFG register to set the granularity of the
aggregation timer, which we configure to be 500 microseconds.

Instead, IPA v4.5 selects between two possible granularity values
derived from the 19.2 MHz Qtime clock.  These granularities are
100 microseconds or 1 millisecond per tick.  We use the smaller
granularity if possible, unless the desired period is too large
to be specified that way.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_endpoint.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index f260c80f50649..b4c884ccb77d2 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -638,14 +638,38 @@ static u32 aggr_byte_limit_encoded(enum ipa_version version, u32 limit)
 	return u32_encode_bits(limit, aggr_byte_limit_fmask(false));
 }
 
+/* Encode the aggregation timer limit (microseconds) based on IPA version */
 static u32 aggr_time_limit_encoded(enum ipa_version version, u32 limit)
 {
-	/* Convert limit (microseconds) to aggregation timer ticks */
-	limit = DIV_ROUND_CLOSEST(limit, IPA_AGGR_GRANULARITY);
-	if (version < IPA_VERSION_4_5)
+	u32 gran_sel;
+	u32 fmask;
+	u32 val;
+
+	if (version < IPA_VERSION_4_5) {
+		/* We set aggregation granularity in ipa_hardware_config() */
+		limit = DIV_ROUND_CLOSEST(limit, IPA_AGGR_GRANULARITY);
+
 		return u32_encode_bits(limit, aggr_time_limit_fmask(true));
+	}
 
-	return u32_encode_bits(limit, aggr_time_limit_fmask(false));
+	/* IPA v4.5 expresses the time limit using Qtime.  The AP has
+	 * pulse generators 0 and 1 available, which were configured
+	 * in ipa_qtime_config() to have granularity 100 usec and
+	 * 1 msec, respectively.  Use pulse generator 0 if possible,
+	 * otherwise fall back to pulse generator 1.
+	 */
+	fmask = aggr_time_limit_fmask(false);
+	val = DIV_ROUND_CLOSEST(limit, 100);
+	if (val > field_max(fmask)) {
+		/* Have to use pulse generator 1 (millisecond granularity) */
+		gran_sel = AGGR_GRAN_SEL_FMASK;
+		val = DIV_ROUND_CLOSEST(limit, 1000);
+	} else {
+		/* We can use pulse generator 0 (100 usec granularity) */
+		gran_sel = 0;
+	}
+
+	return gran_sel | u32_encode_bits(val, fmask);
 }
 
 static u32 aggr_sw_eof_active_encoded(enum ipa_version version, bool enabled)
-- 
2.20.1