[PATCH v5 0/6] bcm2835: auxiliar device support for spi

Martin Sperl kernel at martin.sperl.org
Thu Sep 10 08:57:49 PDT 2015

> On 10.09.2015, at 17:48, Noralf Trønnes <noralf at tronnes.org> wrote:
> This looks interesting.
> But there's a challenge with the uart1 and the 8250 driver.
> Phil Elwell has this to say:
> This means that that UART1 isn't an exact clone of a 8250 UART.
> In a particular, the clock divisor is calculated differently.
> A standard 8250 derives the baud rate as clock/(divisor16),
> whereas the BCM2835 mini UART uses clock/(divisor8). This means
> that if you want to use the standard driver then you need to lie
> about the clock frequency, providing a value is twice the real
> value, in order for a suitable divisor to be calculated.
> Ref: https://github.com/raspberrypi/linux/pull/1008#issuecomment-139234607
> So either we need a new uart1 driver or a doubled clock freq. somehow.

Found out the same thing and communicated it to Eric - not 
knowing about the different divider…


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