diff options
| author | Wolfram Sang <wsa+renesas@sang-engineering.com> | 2023-09-06 22:00:21 +0200 |
|---|---|---|
| committer | Wolfram Sang <wsa@kernel.org> | 2023-09-19 11:10:54 +0200 |
| commit | 47280af872367ead8202b8503083b0b4016b667b (patch) | |
| tree | 29e03a3e4dabb9cd1a8472c11a45b822a4e2d8f0 /drivers/i2c/busses | |
| parent | i2c: rcar: properly format a debug output (diff) | |
| download | linux-47280af872367ead8202b8503083b0b4016b667b.tar.xz linux-47280af872367ead8202b8503083b0b4016b667b.zip | |
i2c: rcar: calculate divider instead of brute-forcing it
Instead of trying all values, we can actually compute it as the comment
suggests. It is unclear what the comment means with "involved", it works
nicely.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Diffstat (limited to 'drivers/i2c/busses')
| -rw-r--r-- | drivers/i2c/busses/i2c-rcar.c | 24 |
1 files changed, 8 insertions, 16 deletions
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 4bf47e35094f..2585092bed52 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -303,24 +303,16 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv) round = (round + 500) / 1000; /* - * SCL = ick / (20 + SCGD * 8 + F[(ticf + tr + intd) * ick]) - * - * Calculation result (= SCL) should be less than - * bus_speed for hardware safety - * - * We could use something along the lines of - * div = ick / (bus_speed + 1) + 1; - * scgd = (div - 20 - round + 7) / 8; - * scl = ick / (20 + (scgd * 8) + round); - * (not fully verified) but that would get pretty involved + * SCL = ick / (20 + 8 * SCGD + F[(ticf + tr + intd) * ick]) + * 20 + 8 * SCGD + F[...] = ick / SCL + * SCGD = ((ick / SCL) - 20 - F[...]) / 8 + * Result (= SCL) should be less than bus_speed for hardware safety */ - for (scgd = 0; scgd < 0x40; scgd++) { - scl = ick / (20 + (scgd * 8) + round); - if (scl <= t.bus_freq_hz) - break; - } + scgd = DIV_ROUND_UP(ick, t.bus_freq_hz ?: 1); + scgd = DIV_ROUND_UP(scgd - 20 - round, 8); + scl = ick / (20 + 8 * scgd + round); - if (scgd == 0x40) + if (scgd > 0x3f) goto err_no_val; dev_dbg(dev, "clk %u/%u(%lu), round %u, CDF: %u, SCGD: %u\n", |