Hi Suneel and Piyush,
...
> void octeon_i2c_set_clock(struct octeon_i2c *i2c)
> {
> int tclk, thp_base, inc, thp_idx, mdiv_idx, ndiv_idx, foscl, diff;
> - int thp = 0x18, mdiv = 2, ndiv = 0, delta_hz = 1000000;
> + int mdiv_min = 2;
why is this int while all the other variables moved to be
"unsigned int"?
> + /* starting value on search for lowest diff */
> + const int huge_delta = INITIAL_DELTA_HZ;
this is not needed.
> + /*
> + * Find divisors to produce target frequency, start with large delta
> + * to cover wider range of divisors, note thp = TCLK half period.
> + */
> + unsigned int thp = 0x18, mdiv = 2, ndiv = 0, delta_hz = huge_delta;
> +
> + if (octeon_i2c_is_otx2(to_pci_dev(i2c->dev))) {
you could save this in a boolean at the beginning and keep using
it.
> + thp = 0x3;
as you are here, can we give a meaningful define to 0x18 and 0x3?
> + mdiv_min = 0;
> + }
>
> for (ndiv_idx = 0; ndiv_idx < 8 && delta_hz != 0; ndiv_idx++) {
> /*
> * An mdiv value of less than 2 seems to not work well
> * with ds1337 RTCs, so we constrain it to larger values.
> */
> - for (mdiv_idx = 15; mdiv_idx >= 2 && delta_hz != 0; mdiv_idx--) {
> + for (mdiv_idx = 15; mdiv_idx >= mdiv_min && delta_hz != 0; mdiv_idx--) {
> /*
> * For given ndiv and mdiv values check the
> * two closest thp values.
> */
> tclk = i2c->twsi_freq * (mdiv_idx + 1) * 10;
> tclk *= (1 << ndiv_idx);
> - thp_base = (i2c->sys_freq / (tclk * 2)) - 1;
> + if (octeon_i2c_is_otx2(to_pci_dev(i2c->dev)))
> + thp_base = (i2c->sys_freq / tclk) - 2;
> + else
> + thp_base = (i2c->sys_freq / (tclk * 2)) - 1;
>
> for (inc = 0; inc <= 1; inc++) {
> thp_idx = thp_base + inc;
> if (thp_idx < 5 || thp_idx > 0xff)
> continue;
>
> - foscl = i2c->sys_freq / (2 * (thp_idx + 1));
> + if (octeon_i2c_is_otx2(to_pci_dev(i2c->dev)))
> + foscl = i2c->sys_freq / (thp_idx + 2);
> + else
> + foscl = i2c->sys_freq /
> + (2 * (thp_idx + 1));
I need to trust you on this.
> foscl = foscl / (1 << ndiv_idx);
> foscl = foscl / (mdiv_idx + 1) / 10;
> diff = abs(foscl - i2c->twsi_freq);
> + /* Use it if smaller diff from target */
can you please expand?
> if (diff < delta_hz) {
> delta_hz = diff;
> thp = thp_idx;
> diff --git a/drivers/i2c/busses/i2c-octeon-core.h b/drivers/i2c/busses/i2c-octeon-core.h
> index 9bb9f64fdda0392364638ecbaafe3fab5612baf6..694c24cecb7b144c1021549d1661b040c21bb998 100644
> --- a/drivers/i2c/busses/i2c-octeon-core.h
> +++ b/drivers/i2c/busses/i2c-octeon-core.h
> @@ -7,6 +7,7 @@
> #include <linux/i2c-smbus.h>
> #include <linux/io.h>
> #include <linux/kernel.h>
> +#include <linux/pci.h>
>
> /* Controller command patterns */
> #define SW_TWSI_V BIT_ULL(63) /* Valid bit */
> @@ -98,6 +99,8 @@ struct octeon_i2c_reg_offset {
> #define TWSI_INT(x) (x->roff.twsi_int)
> #define SW_TWSI_EXT(x) (x->roff.sw_twsi_ext)
>
> +#define INITIAL_DELTA_HZ 1000000
This define doesn't need to be in the header, right? Can we move
it in the c file?
Andi
