In the i.MX6 Dual/Quad Reference Manual, the EIM Clock maximum frequency is given as 133 MHz(page 1005). Again, on page 1012, the ACLK, which I assume is the same as AXI clock and is the same as the EIM clock, has a maximum frequency of 133 MHz.
I assume the default value of the EIM clock is 133 MHz. However, on page 1027-1028, the 133 MHz clock is divided by 2 to get 66 MHz. That should be 66.5 MHz. That implies the EIM clock frequency is 132 MHz exactly.
Page 1056 mentions a EIM clock frequency of 104 MHz which seems to be an optional frequency.
On page 81 of the iMX6 Firmware Guide, EIM clock root frequency is given as 132 MHz.
In the i.MX6 Dual/Quad Applications Processor for Industrial Products data sheet, on page 50, note 2 says the maximum EIM operating frequency is 104 MHz.
Page 56 in the same document has a column title of "Max (If 132 MHz is supported by SoC)".
So, what is the default frequency of the EIM clock, exactly? 133.0 MHz? 132.0 MHz? 104.0 MHz?
And, how does one change the frequency of the EIM clock?
According to the current i.MX6 DQ Datasheet (IMX6DQCEC, Rev. 2.3, 07/2013;
footnote under Table 41 “EIM Bus Timing Parameters”) :
“EIM maximum operating frequency is 104 MHz (t = 9.165 ns)”.
This is a hardware EIM restriction, the mentioned in the Datasheet frequency of 104 MHz
relates to external BCLK clock signal, that can be properly driven for external synchronous
devices, using the BCLK as reference clock.
As for (software) clock configuration please use the next bit fields :
Are you sure that “EIM maximum operating frequency is 104 MHz (t = 9.165 ns)”?
Because currently I have a system based on mx6q, which can access a parallel EIM NOR flash,
while the EIM_BCLK outputs 132MHz clock.
I will check it carefully tomorrow.
The recent Datasheet (IMX6DQCEC, Rev. 3, 02/2014) confirms in section
4.9.3 [External Interface Module (EIM)] :
"Maximum operating frequency for EIM datatransfer is 104 MHz. Timing parameters
in this section that are given as a function of register settings or clock periods are valid
for the entire range of allowed frequencies (0–104 MHz)".
Looks like, we can guarantee all parameters in the Datasheet (under all specified environment
conditions) only till 104 MHz.
The MX6Q EIM can work at 132MHz.
I have a parallel NOR flash connected to MX6Q EIM port.
With both the U-boot and the Linux kernel,
we can access the EIM parallel NOR flash with 132MHz.