[PATCH 1/2] Revert "rockchip: spi: fix off-by-one in chunk size computation"

[Jagan Teki]

Hi Philipp,

On Wed, Dec 11, 2019 at 7:10 PM Philipp Tomsich
<philipp.tomsich at theobroma-systems.com> wrote:
>
>
>
> > On 11.12.2019, at 14:26, Jagan Teki <jagan at amarulasolutions.com> wrote:
> >
> > The maximum transfer length (in a single transaction) for the Rockchip
> > SPI controller is 64Kframes (i.e. 0x10000 frames) of 8bit or 16bit
> > frames and is encoded as (num_frames - 1) in CTRLR1.
> >
> > So the 0x10000 is offset value for 64K but the actual size value would
> > be 'minus 1' from 0x10000.
>
> NAK. Please see 2 code lines below your change to see that the “minus 1”
> is applied there… so a todo of 0x10000 will write 0xffff to regs->ctrlr1.
>
> The problem must be somewhere else and this patch will only mask the
> underlying issue.

Please check the below changes. the max transfer size is 64K - 1 which
is 0xffff and we need to write -1 of this to cr1.

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/spi/spi-rockchip.c?id=5185a81c02d4118b11e6cb7b5fbf6f15ff7aff90
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/spi/spi-rockchip.c?id=04b37d2d02c0a5ae2f4e59326ef6deaff18e0456