Re: [PATCH v5] media: rcar-csi2: Correct the selection of hsfreqrange

["Niklas Söderlund" <niklas.soderlund@ragnatech.se>]

Hi Michael and Suresh,

Thanks for your comments Michael.

On 2020-05-04 17:01:22 +0200, Michael Rodin wrote:
> Hello Suresh, Niklas,
> 
> I think that we should not change the structs for PHTW register configuration,
> because there are no "max" values in the table "PHTW Set Values" from the
> Renesas Hardware Manual. The patch looks just wrong. A major issue is also
> that the Hardware Manual does not provide any algorithm, how to select the
> right table entry for the configuration of PHTW and PHYPLL registers, so we
> can not say for sure that the patch is correct. It is also not clear, what
> are the "default" bit rates? It looks like they are made exactly for usage
> in driver code:
>  - both PHTW and PHYPLL tables have "default" values
>  - only PHYPLL (HSFREQRANGE) tables have min/max values and it requires
>    additional rounding in order to hardcode them in a driver
> But these are just my speculations. If they are correct, then the only
> exception, where the patch v2 failed, could be a typo in the Hardware Manual.
> Otherwise patch v2 looks much better to me. I think, we should wait for more
> details from Renesas before fixing this issue. 

I see your point.

As a middle ground as Suresh is having a real problem and the logic in 
the driver is wrong and should be fixed. How about keeping the 
definition of the struct rcsi2_mbps_reg as it is but updating all the 
tables .mbps values from the default to the max value?

> 
> On Thu, Apr 30, 2020 at 03:03:10PM +0900, Suresh Udipi wrote:
> > hsfreqrange should be chosen based on the calculated mbps which
> > is 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 select the first hsfreqrange whose max range[1] is
> > greater than the calculated bit rate.
> > 
> > Calculated value 360Mbps : max range 380.625 mbps is selected
> >  i.e Default 350Mbps  Range [320.625 -380.625 mpbs]
> > 
> > [1] specs r19uh0105ej0200-r-car-3rd-generation.pdf [Table 25.9]
> > 
> > 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
> > 
> > 
> >  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
> > 
> >  drivers/media/platform/rcar-vin/rcar-csi2.c | 282 ++++++++++++++--------------
> >  1 file changed, 141 insertions(+), 141 deletions(-)
> > 
> > diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > index faa9fb2..d45bf80 100644
> > --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> > +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> > @@ -132,63 +132,63 @@ struct phtw_value {
> >  };
> >  
> >  struct rcsi2_mbps_reg {
> > -	u16 mbps;
> >  	u16 reg;
> > +	u16 max;
> >  };
> >  
> >  static const struct rcsi2_mbps_reg phtw_mbps_h3_v3h_m3n[] = {
> > -	{ .mbps =   80, .reg = 0x86 },
> > -	{ .mbps =   90, .reg = 0x86 },
> > -	{ .mbps =  100, .reg = 0x87 },
> > -	{ .mbps =  110, .reg = 0x87 },
> > -	{ .mbps =  120, .reg = 0x88 },
> > -	{ .mbps =  130, .reg = 0x88 },
> > -	{ .mbps =  140, .reg = 0x89 },
> > -	{ .mbps =  150, .reg = 0x89 },
> > -	{ .mbps =  160, .reg = 0x8a },
> > -	{ .mbps =  170, .reg = 0x8a },
> > -	{ .mbps =  180, .reg = 0x8b },
> > -	{ .mbps =  190, .reg = 0x8b },
> > -	{ .mbps =  205, .reg = 0x8c },
> > -	{ .mbps =  220, .reg = 0x8d },
> > -	{ .mbps =  235, .reg = 0x8e },
> > -	{ .mbps =  250, .reg = 0x8e },
> > +	{ .reg = 0x86, .max =  80  },
> > +	{ .reg = 0x86, .max =  90  },
> > +	{ .reg = 0x87, .max =  100 },
> > +	{ .reg = 0x87, .max =  110 },
> > +	{ .reg = 0x88, .max =  120 },
> > +	{ .reg = 0x88, .max =  130 },
> > +	{ .reg = 0x89, .max =  140 },
> > +	{ .reg = 0x89, .max =  150 },
> > +	{ .reg = 0x8a, .max =  160 },
> > +	{ .reg = 0x8a, .max =  170 },
> > +	{ .reg = 0x8b, .max =  180 },
> > +	{ .reg = 0x8b, .max =  190 },
> > +	{ .reg = 0x8c, .max =  205 },
> > +	{ .reg = 0x8d, .max =  220 },
> > +	{ .reg = 0x8e, .max =  235 },
> > +	{ .reg = 0x8e, .max =  250 },
> >  	{ /* sentinel */ },
> >  };
> >  
> >  static const struct rcsi2_mbps_reg phtw_mbps_v3m_e3[] = {
> > -	{ .mbps =   80, .reg = 0x00 },
> > -	{ .mbps =   90, .reg = 0x20 },
> > -	{ .mbps =  100, .reg = 0x40 },
> > -	{ .mbps =  110, .reg = 0x02 },
> > -	{ .mbps =  130, .reg = 0x22 },
> > -	{ .mbps =  140, .reg = 0x42 },
> > -	{ .mbps =  150, .reg = 0x04 },
> > -	{ .mbps =  170, .reg = 0x24 },
> > -	{ .mbps =  180, .reg = 0x44 },
> > -	{ .mbps =  200, .reg = 0x06 },
> > -	{ .mbps =  220, .reg = 0x26 },
> > -	{ .mbps =  240, .reg = 0x46 },
> > -	{ .mbps =  250, .reg = 0x08 },
> > -	{ .mbps =  270, .reg = 0x28 },
> > -	{ .mbps =  300, .reg = 0x0a },
> > -	{ .mbps =  330, .reg = 0x2a },
> > -	{ .mbps =  360, .reg = 0x4a },
> > -	{ .mbps =  400, .reg = 0x0c },
> > -	{ .mbps =  450, .reg = 0x2c },
> > -	{ .mbps =  500, .reg = 0x0e },
> > -	{ .mbps =  550, .reg = 0x2e },
> > -	{ .mbps =  600, .reg = 0x10 },
> > -	{ .mbps =  650, .reg = 0x30 },
> > -	{ .mbps =  700, .reg = 0x12 },
> > -	{ .mbps =  750, .reg = 0x32 },
> > -	{ .mbps =  800, .reg = 0x52 },
> > -	{ .mbps =  850, .reg = 0x72 },
> > -	{ .mbps =  900, .reg = 0x14 },
> > -	{ .mbps =  950, .reg = 0x34 },
> > -	{ .mbps = 1000, .reg = 0x54 },
> > -	{ .mbps = 1050, .reg = 0x74 },
> > -	{ .mbps = 1125, .reg = 0x16 },
> > +	{ .reg = 0x00, .max = 80   },
> > +	{ .reg = 0x20, .max = 90   },
> > +	{ .reg = 0x40, .max = 100  },
> > +	{ .reg = 0x02, .max = 110  },
> > +	{ .reg = 0x22, .max = 130  },
> > +	{ .reg = 0x42, .max = 140  },
> > +	{ .reg = 0x04, .max = 150  },
> > +	{ .reg = 0x24, .max = 170  },
> > +	{ .reg = 0x44, .max = 180  },
> > +	{ .reg = 0x06, .max = 200  },
> > +	{ .reg = 0x26, .max = 220  },
> > +	{ .reg = 0x46, .max = 240  },
> > +	{ .reg = 0x08, .max = 250  },
> > +	{ .reg = 0x28, .max = 270  },
> > +	{ .reg = 0x0a, .max = 300  },
> > +	{ .reg = 0x2a, .max = 330  },
> > +	{ .reg = 0x4a, .max = 360  },
> > +	{ .reg = 0x0c, .max = 400  },
> > +	{ .reg = 0x2c, .max = 450  },
> > +	{ .reg = 0x0e, .max = 500  },
> > +	{ .reg = 0x2e, .max = 550  },
> > +	{ .reg = 0x10, .max = 600  },
> > +	{ .reg = 0x30, .max = 650  },
> > +	{ .reg = 0x12, .max = 700  },
> > +	{ .reg = 0x32, .max = 750  },
> > +	{ .reg = 0x52, .max = 800  },
> > +	{ .reg = 0x72, .max = 850  },
> > +	{ .reg = 0x14, .max = 900  },
> > +	{ .reg = 0x34, .max = 950  },
> > +	{ .reg = 0x54, .max = 1000 },
> > +	{ .reg = 0x74, .max = 1050 },
> > +	{ .reg = 0x16, .max = 1125 },
> >  	{ /* sentinel */ },
> >  };
> >  
> > @@ -201,96 +201,96 @@ static const struct rcsi2_mbps_reg phtw_mbps_v3m_e3[] = {
> >  #define PHYPLL_HSFREQRANGE(n)		((n) << 16)
> >  
> >  static const struct rcsi2_mbps_reg hsfreqrange_h3_v3h_m3n[] = {
> > -	{ .mbps =   80, .reg = 0x00 },
> > -	{ .mbps =   90, .reg = 0x10 },
> > -	{ .mbps =  100, .reg = 0x20 },
> > -	{ .mbps =  110, .reg = 0x30 },
> > -	{ .mbps =  120, .reg = 0x01 },
> > -	{ .mbps =  130, .reg = 0x11 },
> > -	{ .mbps =  140, .reg = 0x21 },
> > -	{ .mbps =  150, .reg = 0x31 },
> > -	{ .mbps =  160, .reg = 0x02 },
> > -	{ .mbps =  170, .reg = 0x12 },
> > -	{ .mbps =  180, .reg = 0x22 },
> > -	{ .mbps =  190, .reg = 0x32 },
> > -	{ .mbps =  205, .reg = 0x03 },
> > -	{ .mbps =  220, .reg = 0x13 },
> > -	{ .mbps =  235, .reg = 0x23 },
> > -	{ .mbps =  250, .reg = 0x33 },
> > -	{ .mbps =  275, .reg = 0x04 },
> > -	{ .mbps =  300, .reg = 0x14 },
> > -	{ .mbps =  325, .reg = 0x25 },
> > -	{ .mbps =  350, .reg = 0x35 },
> > -	{ .mbps =  400, .reg = 0x05 },
> > -	{ .mbps =  450, .reg = 0x16 },
> > -	{ .mbps =  500, .reg = 0x26 },
> > -	{ .mbps =  550, .reg = 0x37 },
> > -	{ .mbps =  600, .reg = 0x07 },
> > -	{ .mbps =  650, .reg = 0x18 },
> > -	{ .mbps =  700, .reg = 0x28 },
> > -	{ .mbps =  750, .reg = 0x39 },
> > -	{ .mbps =  800, .reg = 0x09 },
> > -	{ .mbps =  850, .reg = 0x19 },
> > -	{ .mbps =  900, .reg = 0x29 },
> > -	{ .mbps =  950, .reg = 0x3a },
> > -	{ .mbps = 1000, .reg = 0x0a },
> > -	{ .mbps = 1050, .reg = 0x1a },
> > -	{ .mbps = 1100, .reg = 0x2a },
> > -	{ .mbps = 1150, .reg = 0x3b },
> > -	{ .mbps = 1200, .reg = 0x0b },
> > -	{ .mbps = 1250, .reg = 0x1b },
> > -	{ .mbps = 1300, .reg = 0x2b },
> > -	{ .mbps = 1350, .reg = 0x3c },
> > -	{ .mbps = 1400, .reg = 0x0c },
> > -	{ .mbps = 1450, .reg = 0x1c },
> > -	{ .mbps = 1500, .reg = 0x2c },
> > +	{ .reg = 0x00, .max =   97 },
> > +	{ .reg = 0x10, .max =  107 },
> > +	{ .reg = 0x20, .max =  118 },
> > +	{ .reg = 0x30, .max =  128 },
> > +	{ .reg = 0x01, .max =  139 },
> > +	{ .reg = 0x11, .max =  149 },
> > +	{ .reg = 0x21, .max =  160 },
> > +	{ .reg = 0x31, .max =  170 },
> > +	{ .reg = 0x02, .max =  181 },
> > +	{ .reg = 0x12, .max =  191 },
> > +	{ .reg = 0x22, .max =  202 },
> > +	{ .reg = 0x32, .max =  212 },
> > +	{ .reg = 0x03, .max =  228 },
> > +	{ .reg = 0x13, .max =  224 },
> > +	{ .reg = 0x23, .max =  259 },
> > +	{ .reg = 0x33, .max =  275 },
> > +	{ .reg = 0x04, .max =  301 },
> > +	{ .reg = 0x14, .max =  328 },
> > +	{ .reg = 0x25, .max =  354 },
> > +	{ .reg = 0x35, .max =  380 },
> > +	{ .reg = 0x05, .max =  433 },
> > +	{ .reg = 0x16, .max =  485 },
> > +	{ .reg = 0x26, .max =  538 },
> > +	{ .reg = 0x37, .max =  590 },
> > +	{ .reg = 0x07, .max =  643 },
> > +	{ .reg = 0x18, .max =  695 },
> > +	{ .reg = 0x28, .max =  748 },
> > +	{ .reg = 0x39, .max =  800 },
> > +	{ .reg = 0x09, .max =  853 },
> > +	{ .reg = 0x19, .max =  905 },
> > +	{ .reg = 0x29, .max =  958 },
> > +	{ .reg = 0x3a, .max = 1010 },
> > +	{ .reg = 0x0a, .max = 1063 },
> > +	{ .reg = 0x1a, .max = 1115 },
> > +	{ .reg = 0x2a, .max = 1168 },
> > +	{ .reg = 0x3b, .max = 1220 },
> > +	{ .reg = 0x0b, .max = 1273 },
> > +	{ .reg = 0x1b, .max = 1325 },
> > +	{ .reg = 0x2b, .max = 1378 },
> > +	{ .reg = 0x3c, .max = 1430 },
> > +	{ .reg = 0x0c, .max = 1483 },
> > +	{ .reg = 0x1c, .max = 1500 },
> > +	{ .reg = 0x2c, .max = 1500 },
> >  	{ /* sentinel */ },
> >  };
> >  
> >  static const struct rcsi2_mbps_reg hsfreqrange_m3w_h3es1[] = {
> > -	{ .mbps =   80,	.reg = 0x00 },
> > -	{ .mbps =   90,	.reg = 0x10 },
> > -	{ .mbps =  100,	.reg = 0x20 },
> > -	{ .mbps =  110,	.reg = 0x30 },
> > -	{ .mbps =  120,	.reg = 0x01 },
> > -	{ .mbps =  130,	.reg = 0x11 },
> > -	{ .mbps =  140,	.reg = 0x21 },
> > -	{ .mbps =  150,	.reg = 0x31 },
> > -	{ .mbps =  160,	.reg = 0x02 },
> > -	{ .mbps =  170,	.reg = 0x12 },
> > -	{ .mbps =  180,	.reg = 0x22 },
> > -	{ .mbps =  190,	.reg = 0x32 },
> > -	{ .mbps =  205,	.reg = 0x03 },
> > -	{ .mbps =  220,	.reg = 0x13 },
> > -	{ .mbps =  235,	.reg = 0x23 },
> > -	{ .mbps =  250,	.reg = 0x33 },
> > -	{ .mbps =  275,	.reg = 0x04 },
> > -	{ .mbps =  300,	.reg = 0x14 },
> > -	{ .mbps =  325,	.reg = 0x05 },
> > -	{ .mbps =  350,	.reg = 0x15 },
> > -	{ .mbps =  400,	.reg = 0x25 },
> > -	{ .mbps =  450,	.reg = 0x06 },
> > -	{ .mbps =  500,	.reg = 0x16 },
> > -	{ .mbps =  550,	.reg = 0x07 },
> > -	{ .mbps =  600,	.reg = 0x17 },
> > -	{ .mbps =  650,	.reg = 0x08 },
> > -	{ .mbps =  700,	.reg = 0x18 },
> > -	{ .mbps =  750,	.reg = 0x09 },
> > -	{ .mbps =  800,	.reg = 0x19 },
> > -	{ .mbps =  850,	.reg = 0x29 },
> > -	{ .mbps =  900,	.reg = 0x39 },
> > -	{ .mbps =  950,	.reg = 0x0a },
> > -	{ .mbps = 1000,	.reg = 0x1a },
> > -	{ .mbps = 1050,	.reg = 0x2a },
> > -	{ .mbps = 1100,	.reg = 0x3a },
> > -	{ .mbps = 1150,	.reg = 0x0b },
> > -	{ .mbps = 1200,	.reg = 0x1b },
> > -	{ .mbps = 1250,	.reg = 0x2b },
> > -	{ .mbps = 1300,	.reg = 0x3b },
> > -	{ .mbps = 1350,	.reg = 0x0c },
> > -	{ .mbps = 1400,	.reg = 0x1c },
> > -	{ .mbps = 1450,	.reg = 0x2c },
> > -	{ .mbps = 1500,	.reg = 0x3c },
> > +	{ .reg = 0x00, .max =  110 },
> > +	{ .reg = 0x10, .max =  120 },
> > +	{ .reg = 0x20, .max =  131 },
> > +	{ .reg = 0x30, .max =  141 },
> > +	{ .reg = 0x01, .max =  152 },
> > +	{ .reg = 0x11, .max =  162 },
> > +	{ .reg = 0x21, .max =  173 },
> > +	{ .reg = 0x31, .max =  183 },
> > +	{ .reg = 0x02, .max =  194 },
> > +	{ .reg = 0x12, .max =  204 },
> > +	{ .reg = 0x22, .max =  215 },
> > +	{ .reg = 0x32, .max =  225 },
> > +	{ .reg = 0x03, .max =  241 },
> > +	{ .reg = 0x13, .max =  257 },
> > +	{ .reg = 0x23, .max =  273 },
> > +	{ .reg = 0x33, .max =  275 },
> > +	{ .reg = 0x04, .max =  301 },
> > +	{ .reg = 0x14, .max =  328 },
> > +	{ .reg = 0x05, .max =  354 },
> > +	{ .reg = 0x15, .max =  393 },
> > +	{ .reg = 0x25, .max =  446 },
> > +	{ .reg = 0x06, .max =  498 },
> > +	{ .reg = 0x16, .max =  551 },
> > +	{ .reg = 0x07, .max =  603 },
> > +	{ .reg = 0x17, .max =  656 },
> > +	{ .reg = 0x08, .max =  708 },
> > +	{ .reg = 0x18, .max =  761 },
> > +	{ .reg = 0x09, .max =  813 },
> > +	{ .reg = 0x19, .max =  866 },
> > +	{ .reg = 0x29, .max =  918 },
> > +	{ .reg = 0x39, .max =  971 },
> > +	{ .reg = 0x0a, .max = 1023 },
> > +	{ .reg = 0x1a, .max = 1076 },
> > +	{ .reg = 0x2a, .max = 1128 },
> > +	{ .reg = 0x3a, .max = 1181 },
> > +	{ .reg = 0x0b, .max = 1233 },
> > +	{ .reg = 0x1b, .max = 1286 },
> > +	{ .reg = 0x2b, .max = 1338 },
> > +	{ .reg = 0x3b, .max = 1391 },
> > +	{ .reg = 0x0c, .max = 1443 },
> > +	{ .reg = 0x1c, .max = 1496 },
> > +	{ .reg = 0x2c, .max = 1500 },
> > +	{ .reg = 0x3c, .max = 1500 },
> >  	{ /* sentinel */ },
> >  };
> >  
> > @@ -432,11 +432,11 @@ static int rcsi2_set_phypll(struct rcar_csi2 *priv, unsigned int mbps)
> >  {
> >  	const struct rcsi2_mbps_reg *hsfreq;
> >  
> > -	for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++)
> > -		if (hsfreq->mbps >= mbps)
> > +	for (hsfreq = priv->info->hsfreqrange; hsfreq->max != 0; hsfreq++)
> > +		if (hsfreq->max >= mbps)
> >  			break;
> >  
> > -	if (!hsfreq->mbps) {
> > +	if (!hsfreq->max) {
> >  		dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
> >  		return -ERANGE;
> >  	}
> > @@ -907,11 +907,11 @@ static int rcsi2_phtw_write_mbps(struct rcar_csi2 *priv, unsigned int mbps,
> >  {
> >  	const struct rcsi2_mbps_reg *value;
> >  
> > -	for (value = values; value->mbps; value++)
> > -		if (value->mbps >= mbps)
> > +	for (value = values; value->max; value++)
> > +		if (value->max >= mbps)
> >  			break;
> >  
> > -	if (!value->mbps) {
> > +	if (!value->max) {
> >  		dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
> >  		return -ERANGE;
> >  	}
> > -- 
> > 2.7.4
> > 
> 
> -- 
> Best Regards,
> Michael

-- 
Regards,
Niklas Söderlund