Re: [PATCH v2 3/9] arm: twr-k70f120m: clock driver for Kinetis SoC

[Linus Walleij <linus.walleij@linaro.org>]

On Tue, Jun 30, 2015 at 2:27 PM, Paul Osmialowski <pawelo@king.net.pl> wrote:

> Based on K70P256M150SF3RM.pdf K70 Sub-Family Reference Manual, Rev. 3.
>
> Signed-off-by: Paul Osmialowski <pawelo@king.net.pl>
(...)
> +struct kinetis_sim_regs {
> +       u32 sopt1;      /* System Options Register 1 */
> +       u32 rsv0[1024];
> +       u32 sopt2;      /* System Options Register 2 */
> +       u32 rsv1;
> +       u32 sopt4;      /* System Options Register 4 */
> +       u32 sopt5;      /* System Options Register 5 */
> +       u32 sopt6;      /* System Options Register 6 */
> +       u32 sopt7;      /* System Options Register 7 */
> +       u32 rsv2[2];
> +       u32 sdid;       /* System Device Identification Register */
> +       u32 scgc[KINETIS_SIM_CG_NUMREGS];       /* Clock Gating Regs 1...7 */
> +       u32 clkdiv1;    /* System Clock Divider Register 1 */
> +       u32 clkdiv2;    /* System Clock Divider Register 2 */
> +       u32 fcfg1;      /* Flash Configuration Register 1 */
> +       u32 fcfg2;      /* Flash Configuration Register 2 */
> +       u32 uidh;       /* Unique Identification Register High */
> +       u32 uidmh;      /* Unique Identification Register Mid-High */
> +       u32 uidml;      /* Unique Identification Register Mid Low */
> +       u32 uidl;       /* Unique Identification Register Low */
> +       u32 clkdiv3;    /* System Clock Divider Register 3 */
> +       u32 clkdiv4;    /* System Clock Divider Register 4 */
> +       u32 mcr;        /* Misc Control Register */
> +};

Now there is this design pattern where you copy the datasheet
register map to a struct again.

This is not good if there is a second revision of the hardware and some
registers are shuffled around. IMO it is better to just use #defines
for register
offsets, so you can do exceptions later. Else a new hardware revision
leads to a new struct with new accessor functions etc etc.

Yours,
Linus Walleij