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From: Suresh Udipi <sudipi@jp.adit-jv.com>
To: <niklas.soderlund@ragnatech.se>
Cc: <akiyama@nds-osk.co.jp>, <efriedrich@de.adit-jv.com>,
	<erosca@de.adit-jv.com>, <hverkuil-cisco@xs4all.nl>,
	<jacopo+renesas@jmondi.org>, <laurent.pinchart@ideasonboard.com>,
	<linux-kernel@vger.kernel.org>, <linux-media@vger.kernel.org>,
	<linux-renesas-soc@vger.kernel.org>, <mrodin@de.adit-jv.com>,
	<securitycheck@denso.co.jp>, <sudipi@jp.adit-jv.com>
Subject: [PATCH v2] [RFC] rcar-vin: rcar-csi2: Correct the selection of hsfreqrange
Date: Tue, 17 Mar 2020 16:08:25 +0900
Message-ID: <1584428905-21560-1-git-send-email-sudipi@jp.adit-jv.com> (raw)
In-Reply-To: <20200316130247.GA2258968@oden.dyn.berto.se>

hsfreqrange should be chosen based on the calculated mbps which
is closer to the default bit rate  and within the range as per
table[1]. But current calculation always selects first value which
is greater than or equal to the calculated mbps which may lead
to chosing a wrong range in some cases.

For example for 360 mbps for H3/M3N
Existing logic selects
Calculated value 360Mbps : Default 400Mbps Range [368.125 -433.125 mbps]

This hsfreqrange is out of range.

The logic is changed to get the default value which is closest to the
calculated value [1]

Calculated value 360Mbps : Default 350Mbps  Range [320.625 -380.625 mpbs]

[1] specs r19uh0105ej0200-r-car-3rd-generation.pdf [Table 25.9]

There is one exectpion value 227Mbps, which may cause out of
range.

Fixes: 769afd212b16 ("media: rcar-csi2: add Renesas R-Car MIPI CSI-2 receiver driver")

Signed-off-by: Suresh Udipi <sudipi@jp.adit-jv.com>
Signed-off-by: Kazuyoshi Akiyama <akiyama@nds-osk.co.jp>
---
Changes in v2:
  - Added the boundary check for the maximum bit rate.
  
  - Simplified the logic by remmoving range check 
    as only the closest default value covers most 
    of the use cases.

  - Aligning the commit message based on the above change

 drivers/media/platform/rcar-vin/rcar-csi2.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index faa9fb2..6573625 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -199,6 +199,7 @@ static const struct rcsi2_mbps_reg phtw_mbps_v3m_e3[] = {
 /* PHY Frequency Control */
 #define PHYPLL_REG			0x68
 #define PHYPLL_HSFREQRANGE(n)		((n) << 16)
+#define PHYPLL_HSFREQRANGE_MAX		1500
 
 static const struct rcsi2_mbps_reg hsfreqrange_h3_v3h_m3n[] = {
 	{ .mbps =   80, .reg = 0x00 },
@@ -431,16 +432,23 @@ static int rcsi2_wait_phy_start(struct rcar_csi2 *priv)
 static int rcsi2_set_phypll(struct rcar_csi2 *priv, unsigned int mbps)
 {
 	const struct rcsi2_mbps_reg *hsfreq;
+	const struct rcsi2_mbps_reg *hsfreq_prev = NULL;
 
-	for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++)
-		if (hsfreq->mbps >= mbps)
-			break;
-
-	if (!hsfreq->mbps) {
+	if (mbps > PHYPLL_HSFREQRANGE_MAX) {
 		dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
 		return -ERANGE;
 	}
 
+	for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++) {
+		if (hsfreq->mbps >= mbps)
+			break;
+		hsfreq_prev = hsfreq;
+	}
+
+	if (hsfreq_prev &&
+	    ((mbps - hsfreq_prev->mbps) <= (hsfreq->mbps - mbps)))
+		hsfreq = hsfreq_prev;
+
 	rcsi2_write(priv, PHYPLL_REG, PHYPLL_HSFREQRANGE(hsfreq->reg));
 
 	return 0;
-- 
2.7.4


  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20  4:49 [PATCH] [RFC] media: rcar-csi2: Corrects " Suresh Udipi
2020-03-04 19:46 ` Niklas Söderlund
2020-03-16 13:02   ` Niklas Söderlund
2020-03-17  7:08     ` Suresh Udipi [this message]
2020-03-17 10:37       ` [PATCH v2] [RFC] rcar-vin: rcar-csi2: Correct " Niklas Söderlund
2020-03-18  9:00         ` Suresh Udipi
2020-03-18 10:19           ` Niklas Söderlund
2020-03-20  8:00             ` [PATCH v3] media: " Suresh Udipi
2020-03-23  4:48               ` [PATCH v4] " Suresh Udipi
2020-04-14 11:56                 ` Niklas Söderlund
2020-04-30  6:03                   ` [PATCH v5] " Suresh Udipi
2020-05-04 15:01                     ` Michael Rodin
2020-05-12 21:30                       ` Niklas Söderlund
2020-05-27 15:47                         ` Michael Rodin
2020-05-27 16:16                         ` [PATCH] rcar-vin: " Michael Rodin
2020-06-05 18:44                           ` Michael Rodin
2020-06-08  3:25                             ` [PATCH v6] media: " Suresh Udipi
2020-06-10 13:40                               ` Niklas Söderlund
2020-06-12  3:10                                 ` Suresh Udipi
2020-06-12 17:28                                   ` Michael Rodin
2020-06-15 14:11                                     ` Niklas Söderlund
2020-06-17  4:57                                       ` [PATCH v7 1/2] " Suresh Udipi
2020-06-17  4:57                                         ` [PATCH v7 2/2] media: rcar-csi2: Add warning for PHY speed less than minimum Suresh Udipi
2020-06-17 13:37                                         ` [PATCH v7 1/2] media: rcar-csi2: Correct the selection of hsfreqrange Michael Rodin
2020-06-18 10:34                                           ` [PATCH v8 1/3] " Suresh Udipi
2020-06-18 10:34                                             ` [PATCH v8 2/3] media: rcar-csi2: Add warning for PHY speed less than minimum Suresh Udipi
2020-06-30 22:05                                               ` Niklas Söderlund
2020-06-18 10:34                                             ` [PATCH v8 3/3] media: rcar-csi2: Optimize the selection PHTW register Suresh Udipi
2020-06-30 22:08                                               ` Niklas Söderlund
2020-07-01  9:52                                                 ` [PATCH v9 1/3] media: rcar-csi2: Correct the selection of hsfreqrange Suresh Udipi
2020-07-01  9:53                                                   ` [PATCH v9 2/3] media: rcar-csi2: Add warning for PHY speed less than minimum Suresh Udipi
2020-07-01  9:53                                                   ` [PATCH v9 3/3] media: rcar-csi2: Optimize the selection PHTW register Suresh Udipi
2020-06-30 22:03                                             ` [PATCH v8 1/3] media: rcar-csi2: Correct the selection of hsfreqrange Niklas Söderlund
2020-05-27 16:17                         ` [PATCH] rcar-vin: rcar-csi2: Select the correct PHTW register Michael Rodin

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