Changes between Version 6 and Version 7 of faq


Ignore:
Timestamp:
03/01/2018 09:49:57 PM (20 months ago)
Author:
Ryan Erbstoesser
Comment:

add faq for sdma

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  • faq

    v6 v7  
    185185
    186186This is highly dependent on the amount of data being passed between the access point and client. If each client is streaming video from the AP, then the limit will be much smaller (estimate 3-10). If each client is only querying a small HTML webpage, this limit could be higher (estimate 15-30). There is no 'defined' limit and Gateworks recommends testing with the exact hardware (variations between processor speed, cores, memory, wireless technology, etc). One third party company has a solution to handle many clients, shown [wiki:eblast/intelligent-access-point here]
     187
     188== What is this imx-sdma message and is it an error? ==
     189
     190It is common to see the line on Ventana boards:
     191{{{
     192[   60.366404] imx-sdma 20ec000.sdma: external firmware not found, using ROM firmware
     193}}}
     194
     195SDMA: Smart Dynamic Memory Allocation.
     196
     197The sdma firmware was removed from our OpenWrt BSP because it is no longer necessary any longer.
     198
     199It was needed for imx i2s audio in general but now the upstream kernel drivers have been modified to no longer need it. The licensing of this firmware was keeping it out of OpenWrt upstream which is why we wanted to remove it.
     200
     201The message itself isn't an error. We could remove the firmware loading altogether but they haven't done that upstream in Linux so we don't think it would be right for us to do it in OpenWrt's kernel.
     202
     203There are many kernel messages that sometimes are misleading, making people think there is an error when it is nothing to be concerned about.
     204
     205
     206This message may sit on the console for a little while, but if you hit the return key on your keyboard, you can quickly get a command prompt earlier.
     207
     208You can try to remove this by modifying the device tree, but note Gateworks has not tried or tested this:
     209 * https://github.com/Gateworks/linux-imx6/blob/gateworks_fslc_3.14_1.0.x_ga/arch/arm/boot/dts/imx6qdl.dtsi#L841
     210
     211
     212
     213Here are some links you can read more about the Freescale CPU:
     214 * https://www.kernel.org/doc/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
     215 * https://www.nxp.com/products/microcontrollers-and-processors/arm-based-processors-and-mcus/i.mx-applications-processors/i.mx-6-processors:IMX6X_SERIES
     216 * https://community.nxp.com