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

Linus Walleij
2015-07-14T09:03:59Z

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