Hi Geert, > -----Original Message----- > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Sent: 16 March 2025 09:53 > Subject: Re: [PATCH v4 08/11] can: rcar_canfd: Add shift table to struct rcar_canfd_hw_info > > Hi Biju, > > On Sat, 15 Mar 2025 at 18:31, Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote: > > > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> On Thu, 6 Mar 2025 > > > at 13:43, Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote: > > > > R-Car Gen3 and Gen4 has some differences in the shift bits. Add a > > > > shift table to handle these differences. After this drop the > > > > unused functions reg_gen4() and is_gen4(). > > > > > > > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> > > > > > > Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > > > > > > A suggestion for improvement below. > > > > > > > --- a/drivers/net/can/rcar/rcar_canfd.c > > > > +++ b/drivers/net/can/rcar/rcar_canfd.c > > > > @@ -90,11 +90,13 @@ > > > > /* RSCFDnCFDGAFLCFG0 / RSCFDnGAFLCFG0 */ #define > > > > RCANFD_GAFLCFG_SETRNC(gpriv, n, x) \ > > > > (((x) & (gpriv)->info->mask_table[RCANFD_RNC_MASK]) << \ > > > > - (reg_gen4(gpriv, 16, 24) - ((n) & 1) * reg_gen4(gpriv, 16, 8))) > > > > + ((gpriv)->info->shift_table[RCANFD_FIRST_RNC_SH] - ((n) & 1) * \ > > > > + (gpriv)->info->shift_table[RCANFD_SECOND_RNC_SH])) > > > > > > Both shifts are dictated by the field width: > > > - R-Car Gen4 packs 2 values in a 32-bit word, using a field width > > > of 16 bits, > > > - R-Car Gen3 packs up to 4 values in a 32-bit word, using a field > > > width of 8 bits. > > > The odd split in two shifts is due to the MSB-first numbering of the > > > fields. Hence I think it would be better to use a field width > > > parameter, and derive the proper shift value from that (like you > > > have already done for ICU ;-) > > > > > > Note that the formula will have to be reworked anyway to support the > > > third channel on R-Car V3H_2, as "n & "1 will no longer fly here... > > > > Agreed. Will introduce rnc_field_width variable in struct > > rcar_canfd_hw_info and Simplify the calculation using the formula (32 - (n + 1) * rnc_field_width). > > Which will work for third channel on R-Car V3H_2 as well. > > Note that you still need to mask n, as n can be up to 7 (on R-Car V4H), while the register holds only > 2 or 4 values. OK, will add separate patch for fixing -#define RCANFD_GAFLCFG(ch) (0x009c + (0x04 * ((ch) / 2))) +#define RCANFD_GAFLCFG(ch, n) (0x009c + (0x04 * ((ch) / (n)))) Where n is gpriv->info->rnc_per_reg. and SETRNC is simplified to #define RCANFD_GAFLCFG_SETRNC(gpriv, n, x) \ (((x) & ((gpriv)->info->num_supported_rules - 1)) << \ - (reg_gen4(gpriv, 16, 24) - ((n) & 1) * reg_gen4(gpriv, 16, 8))) + (32 - (((n) % (gpriv)->info->rnc_per_reg + 1) * (gpriv)->info->rnc_field_width))) Cheers, Biju
