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SubjectRe: [PATCH v2 1/2] serial: dz: xmit buffer is UART_XMIT_SIZE'd
On Thu, 25 Aug 2022, Ilpo Järvinen wrote:

> In theory, the Tx code would be buggy if UART_XMIT_SIZE differs from
> 4096 (occurs when PAGE_SIZE > 4k), however, given the lack of issue
> reports such configuration likely doesn't occur with any real platform
> with dz HW. The inconsisted sizes would cause missing characters and
> never-ending bogus Tx when ->head reaches the region above 4k. The
> issue, if it would be real, would predate git days.

This is misleading. There are exactly 3 machine models (2 major ones and
1 extra submodel) that we currently support which make use of this serial
port hardware and driver, and they all have their R2000/R3000 MIPS CPU
soldered onto their respective mainboards. And the CPUs they use all have
their page size hardwired to 4KiB, so it's not the lack of reports, but a
firm assertion that this driver as it stands shall never be used with a
different page size.

There exists an option card using a DZ11-compatible chipset that can be
used with systems we currently support with page sizes of up to 64KiB, but
to the best of my knowledge only a number of prototype cards has been made
and I have heard of exactly one person having such a card. Therefore we
do not support it and may never do, so it is not a concern for the driver
as it stands and shall not be mentioned.

Please just state then that the change is for design consistency with the
serial core and redefine DZ_XMIT_SIZE in terms of UART_XMIT_SIZE as I
suggested for v1. I'll ack such a change. Please drop 2/2 at this stage
as it does not fix any bug and does not appear to add any value to this
driver.

Thanks,

Maciej

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