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Date: Wed, 10 Jun 2020 15:40:04 +0200
From: Niklas Söderlund
<niklas.soderlund@...natech.se>
To: Suresh Udipi <sudipi@...adit-jv.com>
Cc: mrodin@...adit-jv.com, efriedrich@...adit-jv.com,
erosca@...adit-jv.com, linux-kernel@...r.kernel.org,
linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
mchehab@...nel.org, michael@...in.online,
securitycheck@...so.co.jp,
Kazuyoshi Akiyama <akiyama@...-osk.co.jp>
Subject: Re: [PATCH v6] media: rcar-csi2: Correct the selection of hsfreqrange
Hi Suresh,
Thanks for your persistent work!
On 2020-06-08 12:25:03 +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]
>
> Please note that According to Renesas in Table 25.9 the range for
> 220 default value is corrected as below
>
> |Range (Mbps) | Default Bit rate (Mbps) |
> -----------------------------------------------
> | 197.125-244.125 | 220 |
> -----------------------------------------------
>
> Fixes: 769afd212b16 ("media: rcar-csi2: add Renesas R-Car MIPI CSI-2 receiver driver")
>
> Signed-off-by: Suresh Udipi <sudipi@...adit-jv.com>
> Signed-off-by: Kazuyoshi Akiyama <akiyama@...-osk.co.jp>
> Signed-off-by: Michael Rodin <mrodin@...adit-jv.com>
> ---
> 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
>
>
> Changes in v3:
> - Added max member from struct rcsi2_mbps_reg.
> mbps varialbe cannot be removed from rcsi2_mbps_reg,
> since this structure is reused for
> phtw_mbps_h3_v3h_m3n/phtw_mbps_v3m_e3 where mbps is
> used.
>
>
> - Update the walk of the array in rcsi2_set_phypll() so that it finds
> the first entry where the calculated bit rate is less than the max.
>
> - Support lower bit rates less than 80Mbps like 48Mbps
> (Raspberry pi camera 640x480 connected to Kingfisher)
> can also be supported by selecting the lowest default bit rate 80Mbps
> as done before this fix
>
> - Alignement of the commit message based on above changes.
>
> Changes in v4:
> - Remove unncessary braces.
>
> Changes in v5:
> - Removed mbps variable in rcsi2_mbps_reg and aligned all
> tables accordingly
>
> Changes in v6
> - Renesas correct the range of default value 220Mbps. Now
> if we select the nearest value to the default value all
> the values are in range. So reverting back to original patch
>
> - Added warning for values less than Minimum 80Mbps
>
>
> drivers/media/platform/rcar-vin/rcar-csi2.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> index 151e6a9..8c502b7 100644
> --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> @@ -199,6 +199,8 @@ 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
> +#define PHYPLL_HSFREQRANGE_MIN 80
>
> static const struct rcsi2_mbps_reg hsfreqrange_h3_v3h_m3n[] = {
> { .mbps = 80, .reg = 0x00 },
> @@ -431,16 +433,27 @@ 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;
> }
>
> + if (mbps < PHYPLL_HSFREQRANGE_MIN)
> + dev_warn(priv->dev, "PHY speed (%u Mbps) less \
> + than Min 80Mbps\n", mbps);
I would drop this warning.
> +
> + 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)))
Longer lines are now OK [1] and I think it would add to the readability
here.
> + hsfreq = hsfreq_prev;
> +
How about
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;
hsfreq_prev = hsfreq;
}
if (!hsfreq->mbps) {
dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
return -ERANGE;
}
if (hsfreq_prev && ((mbps - hsfreq_prev->mbps) <= (hsfreq->mbps - mbps)))
hsfreq = hsfreq_prev;
rcsi2_write(priv, PHYPLL_REG, PHYPLL_HSFREQRANGE(hsfreq->reg));
return 0;
}
> rcsi2_write(priv, PHYPLL_REG, PHYPLL_HSFREQRANGE(hsfreq->reg));
>
> return 0;
> --
> 2.7.4
>
1. https://lkml.org/lkml/2020/5/29/1038
--
Regards,
Niklas Söderlund
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