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From: "Niklas Söderlund" <niklas.soderlund@ragnatech.se>
To: Suresh Udipi <sudipi@jp.adit-jv.com>
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
Subject: Re: [PATCH v2] [RFC] rcar-vin: rcar-csi2: Correct the selection of hsfreqrange
Date: Tue, 17 Mar 2020 11:37:56 +0100	[thread overview]
Message-ID: <20200317103756.GC2496015@oden.dyn.berto.se> (raw)
In-Reply-To: <1584428905-21560-1-git-send-email-sudipi@jp.adit-jv.com>

Hi Suresh,

Thanks for your work.

On 2020-03-17 16:08:25 +0900, Suresh Udipi wrote:
> 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.

Then something else is needed I think :-)

I liked v1 of this RFC more, where you added a u16 min and max to struct 
rcsi2_mbps_reg. I think that is the right solution.

What I tried to express in my review of v1 was

- You should remove the mbps member from struct rcsi2_mbps_reg.
- Update the walk of the array in rcsi2_set_phypll() so that it finds 
  the first entry where the calculated target value is between min and 
  max and use the reg setting for that entry.

Would that solution make sens too you? Sorry if I expressed myself a but 
muddy in v1 about this.

> 
> 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
> 

-- 
Regards,
Niklas Söderlund

  reply	other threads:[~2020-03-17 10:38 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20  4:49 [PATCH] [RFC] media: rcar-csi2: Corrects the selection of hsfreqrange Suresh Udipi
2020-03-04 19:46 ` Niklas Söderlund
2020-03-16 13:02   ` Niklas Söderlund
2020-03-17  7:08     ` [PATCH v2] [RFC] rcar-vin: rcar-csi2: Correct " Suresh Udipi
2020-03-17 10:37       ` Niklas Söderlund [this message]
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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