linux-kernel - [PATCH v2 2/2] slimbus: qcom-ngd-ctrl: add support for 44.1 Khz frequency

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Message-Id: <20220930100015.259106-2-krzysztof.kozlowski@linaro.org>
Date:   Fri, 30 Sep 2022 12:00:15 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Prudhvi Yarlagadda <pyarlaga@...eaurora.org>
Subject: [PATCH v2 2/2] slimbus: qcom-ngd-ctrl: add support for 44.1 Khz frequency

Add support for 44.1Khz frequency by dynamically calculating the slimbus
parameters instead of statically defining them.

Co-developed-by: Prudhvi Yarlagadda <pyarlaga@...eaurora.org>
Signed-off-by: Prudhvi Yarlagadda <pyarlaga@...eaurora.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

---

Changes since v1:
1. Rebase (drop development pieces in the context).
---
 drivers/slimbus/qcom-ngd-ctrl.c | 64 ++++++++++++++++++++++++++++++---
 1 file changed, 59 insertions(+), 5 deletions(-)

diff --git a/drivers/slimbus/qcom-ngd-ctrl.c b/drivers/slimbus/qcom-ngd-ctrl.c
index ac84fdc2822f..051ac5cba207 100644
--- a/drivers/slimbus/qcom-ngd-ctrl.c
+++ b/drivers/slimbus/qcom-ngd-ctrl.c
@@ -944,6 +944,54 @@ static int qcom_slim_ngd_xfer_msg_sync(struct slim_controller *ctrl,
 	return ret;
 }
 
+static int qcom_slim_calc_coef(struct slim_stream_runtime *rt, int *exp)
+{
+	struct slim_controller *ctrl = rt->dev->ctrl;
+	int coef;
+
+	if (rt->ratem * ctrl->a_framer->superfreq < rt->rate)
+		rt->ratem++;
+
+	coef = rt->ratem;
+	*exp = 0;
+
+	/*
+	 * CRM = Cx(2^E) is the formula we are using.
+	 * Here C is the coffecient and E is the exponent.
+	 * CRM is the Channel Rate Multiplier.
+	 * Coefficeint should be either 1 or 3 and exponenet
+	 * should be an integer between 0 to 9, inclusive.
+	 */
+	while (1) {
+		while ((coef & 0x1) != 0x1) {
+			coef >>= 1;
+			*exp = *exp + 1;
+		}
+
+		if (coef <= 3)
+			break;
+
+		coef++;
+	}
+
+	/*
+	 * we rely on the coef value (1 or 3) to set a bit
+	 * in the slimbus message packet. This bit is
+	 * BIT(5) which is the segment rate coefficient.
+	 */
+	if (coef == 1) {
+		if (*exp > 9)
+			return -EIO;
+		coef = 0;
+	} else {
+		if (*exp > 8)
+			return -EIO;
+		coef = 1;
+	}
+
+	return coef;
+}
+
 static int qcom_slim_ngd_enable_stream(struct slim_stream_runtime *rt)
 {
 	struct slim_device *sdev = rt->dev;
@@ -967,16 +1015,22 @@ static int qcom_slim_ngd_enable_stream(struct slim_stream_runtime *rt)
 		struct slim_port *port = &rt->ports[i];
 
 		if (txn.msg->num_bytes == 0) {
-			int seg_interval = SLIM_SLOTS_PER_SUPERFRAME/rt->ratem;
-			int exp;
+			int exp = 0, coef = 0;
 
 			wbuf[txn.msg->num_bytes++] = sdev->laddr;
 			wbuf[txn.msg->num_bytes] = rt->bps >> 2 |
 						   (port->ch.aux_fmt << 6);
 
-			/* Data channel segment interval not multiple of 3 */
-			exp = seg_interval % 3;
-			if (exp)
+			/* calculate coef dynamically */
+			coef = qcom_slim_calc_coef(rt, &exp);
+			if (coef < 0) {
+				dev_err(&sdev->dev,
+				"%s: error calculating coef %d\n", __func__,
+									coef);
+				return -EIO;
+			}
+
+			if (coef)
 				wbuf[txn.msg->num_bytes] |= BIT(5);
 
 			txn.msg->num_bytes++;
-- 
2.34.1