The audio and video PLLs are designed to have a precision of 1 Hz if some
conditions are met. The current implementation only allows a precision that
depends on the rate of the parent clock. E.g., if the parent clock is 24
MHz, the precision will be 24 Hz; or more generally the precision will be
p / 10^6 Hz
where p is the parent clock rate. This comes down to how the register
values for the PLL's fractional loop divider are chosen.
The clock rate calculation for the PLL is
PLL output frequency = Fref * (DIV_SELECT + NUM / DENOM)
or with a shorter notation
r = p * (d + a / b)
In addition to all variables being integers, we also have the following
conditions:
27 <= d <= 54
-2^29 <= a <= 2^29-1
0 < b <= 2^30-1
|a| < b
Here, d, a and b are register values for the fractional loop divider. We
want to chose d, a and b such that f(p, r) = p, i.e. f is our round_rate
function. Currently, d and b are chosen as
d = r / p
b = 10^6
hence we get the poor precision. And a is defined in terms of r, d, p and
b:
a = (r - d * p) * b / p
I propose that if p <= 2^30-1 (i.e., the max value for b), we chose b as
b = p
We can do this since
|a| < b
|(r - d * p) * b / p| < b
|r - d * p| < p
Which have two solutions, one of them is when p < 0, so we can skip that
one. The other is when p > 0 and
p * (d - 1) < r < p * (d + 1)
Substitute d = r / p:
(r - p) < r < (r + p) <=> p > 0
So, as long as p > 0, we can chose b = p. This is a good choise for b since
a = (r - d * p) * b / p
= (r - d * p) * p / p
= r - d * p
r = p * (d + a / b)
= p * d + p * a / b
= p * d + p * a / p
= p * d + a
and if d = r / p:
a = r - d * p
= r - r / p * p
= 0
r = p * d + a
= p * d + 0
= p * r / p
= r
I reckon this is the intention by the design of the clock rate formula.
Signed-off-by: Emil Lundmark <emil@limesaudio.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Since 'parent_rate * mfn' may overflow 32 bits, the result should be
stored using 64 bits.
The problem was discovered when trying to set the rate of the audio PLL
(pll4_post_div) on an i.MX6Q. The desired rate was 196.608 MHz, but
the actual rate returned was 192.000570 MHz. The round rate function should
have been able to return 196.608 MHz, i.e., the desired rate.
Fixes: ba7f4f557e ("clk: imx: correct AV PLL rate formula")
Cc: Anson Huang <b20788@freescale.com>
Signed-off-by: Emil Lundmark <emil@limesaudio.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
The powerdown bit is a bit confused, let's change it to power_bit
to relfect both powerdown and powerup case according to different
plls.
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
After commit f53947456f ("ARM: clk: imx: update pllv3 to support imx7"),
the former used BM_PLL_POWER bit is not correct anymore for IMX7 ENET.
Instead, pll->powerdown holds the correct bit, so using powerdown bit
in clk_pllv3_{prepare | unprepare} functions.
Fixes: f53947456f ("ARM: clk: imx: update pllv3 to support imx7")
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
The audio/video PLL's rate calculation is as below in RM:
Fref * (DIV_SELECT + NUM / DENOM), in origin clk-pllv3's
code, below code is used:
(parent_rate * div) + ((parent_rate / mfd) * mfn
as it does NOT consider the float data using div, so below
formula should be used as a decent method:
(parent_rate * div) + ((parent_rate * mfn) / mfd)
and we also need to consider parent_rate * mfd may overflow
a 32 bit value, 64 bit value should be used.
After updating this formula, the dram PLL's rate is
1066MHz, which is correct, while the old formula gets
1056MHz.
[Aisheng: fix clk_pllv3_av_round_rate too]
Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
The i.MX 7 designs Ethernet PLL provides a 1000MHz reference clock.
Store the reference clock in the clk_pllv3 structure according to
the PLL type.
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Add 'is_prepared' callback function for pllv3 type clk to make sure when
the system is bootup, the unused clk is in a known state to match the
prepare count info.
Signed-off-by: Bai Ping <b51503@freescale.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Clock provider drivers generally shouldn't include clk.h because
it's the consumer API. Remove the include here because this is a
provider driver.
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
The definition of do_div uses unsigned long long
variable as its first parameter, better to pass
a u64 variable as first parameter when calling
do_div function.
Signed-off-by: Anson Huang <b20788@freescale.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
After the cleanup on clock drivers, they are now ready to be moved into
drivers/clk. Let's move them into drivers/clk/imx folder.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Emil Lundmark