On Wed, Jun 10, 2020 at 03:40:04PM +0200, Niklas Söderlund wrote:
> 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@xxxxxxxxxxxxxx>
> > Signed-off-by: Kazuyoshi Akiyama <akiyama@xxxxxxxxxxxxx>
> > Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> > ---
> > 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.
>
This was suggested by Michael. Michael is it ok to drop this warning
as it is not available before this changes also.
> > +
> > + 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;
Agreed I will do the changes and update.
> > --
> > 2.7.4
> >
>
> 1. https://lkml.org/lkml/2020/5/29/1038
>
> --
> Regards,
> Niklas Söderlund
--
Best Regards,
Suresh Udipi.
