[PATCH 0/2] spi: imx: don't loop endlessly

Uwe Kleine-König u.kleine-koenig at pengutronix.de
Sun Oct 1 22:31:23 PDT 2017

On Fri, Sep 29, 2017 at 08:08:28PM +0200, Alexander Kurz wrote:
> Hi,
> during xchg_single 32 bits will be sent and received:
> 2x32 bits / 10 Microseconds = 6.4MHz Clock.

why 2x?

> Hence, a 10 Microseconds timeout will break SPI communication for
> boards with SPI frequencies less then 6.4MHz.
> On some boards spi-max-frequency is limited due to improper communication
> at higher frequencies, e.g. for the kindle4 it is 1MHz and there 
> also exists one board with 100kHz.
> Before sending a patch calculating the timeout from spi-max-frequency,
> is 640 Microseconds (to fit imx28-cfa10049.dts 100kHz) acceptable?

I would expect that the hardware and software add some latency, so maybe
round it up to 1 ms?

Best regards

Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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