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SubjectRe: [PATCH 11/11] spi: pxa2xx: Deal with the leftover garbage in TXFIFO
On Wed 2018-10-10 19:09:36, Lubomir Rintel wrote:
> There doesn't seem to be a way to empty TXFIFO on MMP2. The datasheet is
> super-secret and the method described in Armada 16x manual won't work:
>
> "The TXFIFO and RXFIFO are cleared to 0b0 when the SSPx port is reset or
> disabled (by writing a 0b0 to the <Synchronous Serial Port Enable> field
> in the SSP Control Register 0)."
>
> # devmem 0xd4037008 # read SSSR
> 0x0000F204
> # devmem 0xd4037000 32 0x80 # SSE off in SSCR0
> # devmem 0xd4037000 32 0x87 # SSE on
> # devmem 0xd4037008
> 0x0000F204
> ^ TXFIFO level is still 2. Sigh.
>
> The OLPC 1.75 boot firmware leaves two bytes in the TXFIFO. Those are
> basically throwaway bytes used in response to the messages from the EC.
> The OLPC kernel copes with this by power-cycling the hardware. Perhaps
> the firmware should do this instead.
>
> Other than that, there's not much we can do other than complain loudly
> until the garbage gets drained and discard the actual data... For the
> OLPC EC this will work just fine and pushing more data to TXFIFO would
> break further transactions.
>
> Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

Acked-by: Pavel Machek <pavel@ucw.cz>

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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