Re: [PATCH 1/3] i2c: thunderx: Clock divisor logic changes

Andi Shyti
2023-06-10T12:30:08Z

Hi Suneel and Piuysh,

On Thu, Mar 30, 2023 at 06:39:51AM -0700, Piyush Malgujar wrote:
> From: Suneel Garapati <sgarapati@marvell.com>
>
> Handle changes to clock divisor logic for OcteonTX2 SoC family using
> subsystem ID and using default reference clock source as 100MHz.
>
> Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
> Signed-off-by: Piyush Malgujar <pmalgujar@marvell.com>
> ---
> drivers/i2c/busses/i2c-octeon-core.c | 29 ++++++++++++++++++++----
> drivers/i2c/busses/i2c-octeon-core.h | 15 ++++++++++++
> drivers/i2c/busses/i2c-thunderx-pcidrv.c | 6 +++++
> 3 files changed, 46 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-octeon-core.c b/drivers/i2c/busses/i2c-octeon-core.c
> index 845eda70b8cab52a0453c9f4cb545010fba4305d..dfd58bbec47b1f0554ae0c100c680b6ba9be61ec 100644
> --- a/drivers/i2c/busses/i2c-octeon-core.c
> +++ b/drivers/i2c/busses/i2c-octeon-core.c
> @@ -17,6 +17,7 @@
> #include <linux/interrupt.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> +#include <linux/pci.h>
>
> #include "i2c-octeon-core.h"
>
> @@ -658,31 +659,51 @@ int octeon_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> 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;
> + /* starting value on search for lowest diff */
> + const int huge_delta = 1000000;

would be nice to have this "1000000" value defined, also because
it's used in other parts of the code.

> + /*
> + * Find divisors to produce target frequency, start with large delta
> + * to cover wider range of divisors, note thp = TCLK half period.
> + */
> + int thp = 0x18, mdiv = 2, ndiv = 0, delta_hz = huge_delta;

as you are changing them, they can also be unsigned.

Patch looks good to me and, even if it's not breaking anything
from the previous platforms, would be nice to have a comment from
Robert.

With the above comments:

Acked-by: Andi Shyti <andi.shyti@kernel.org>

Thanks,
Andi

> +
> + if (octeon_i2c_is_otx2(to_pci_dev(i2c->dev))) {
> + thp = 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));
> foscl = foscl / (1 << ndiv_idx);
> foscl = foscl / (mdiv_idx + 1) / 10;
> diff = abs(foscl - i2c->twsi_freq);
> + /* Use it if smaller diff from target */
> 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..8a0033c94a8a291fb255b0da03858274035c46f4 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 */
> @@ -211,6 +212,20 @@ static inline void octeon_i2c_write_int(struct octeon_i2c *i2c, u64 data)
> octeon_i2c_writeq_flush(data, i2c->twsi_base + TWSI_INT(i2c));
> }
>
> +#define PCI_SUBSYS_DEVID_9XXX 0xB
> +/**
> + * octeon_i2c_is_otx2 - check for chip ID
> + * @pdev: PCI dev structure
> + *
> + * Returns TRUE if OcteonTX2, FALSE otherwise.
> + */
> +static inline bool octeon_i2c_is_otx2(struct pci_dev *pdev)
> +{
> + u32 chip_id = (pdev->subsystem_device >> 12) & 0xF;
> +
> + return (chip_id == PCI_SUBSYS_DEVID_9XXX);
> +}
> +
> /* Prototypes */
> irqreturn_t octeon_i2c_isr(int irq, void *dev_id);
> int octeon_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num);
> diff --git a/drivers/i2c/busses/i2c-thunderx-pcidrv.c b/drivers/i2c/busses/i2c-thunderx-pcidrv.c
> index a77cd86fe75ed7401bc041b27c651b9fedf67285..eecd27f9f1730e522dcccafc9f12ea891a3b59ef 100644
> --- a/drivers/i2c/busses/i2c-thunderx-pcidrv.c
> +++ b/drivers/i2c/busses/i2c-thunderx-pcidrv.c
> @@ -205,6 +205,12 @@ static int thunder_i2c_probe_pci(struct pci_dev *pdev,
> if (ret)
> goto error;
>
> + /*
> + * For OcteonTX2 chips, set reference frequency to 100MHz
> + * as refclk_src in TWSI_MODE register defaults to 100MHz.
> + */
> + if (octeon_i2c_is_otx2(pdev))
> + i2c->sys_freq = 100000000;
> octeon_i2c_set_clock(i2c);
>
> i2c->adap = thunderx_i2c_ops;
> --
> 2.17.1
>