[PATCH] serial: 8250: Fix ...console_fifo_write on BCM283x

Phil Elwell phil at raspberrypi.com
Wed Jan 26 06:27:38 PST 2022

Hi Greg,

On 26/01/2022 14:21, Greg Kroah-Hartman wrote:
> On Wed, Jan 26, 2022 at 02:11:24PM +0000, Phil Elwell wrote:
>> The mini-UART on BCM283x is doubly crippled - it has 8-byte FIFOs and
>> the THRE bit indicates that the TX FIFO is not-full rather than empty.
>> The optimisation to enable the use of the FIFO assumes that it is safe
>> to write fifosize bytes whenever THRE is set, but the BCM283x quirk
>> (indicated by the presence of UART_CAP_MINI) makes it necessary to
>> check the FIFO state after each byte.
>> See: https://github.com/raspberrypi/linux/issues/4849
>> Fixes: 5021d709b31b ("tty: serial: Use fifo in 8250 console driver")
> I have just reverted this commit, it's broken for many platforms now,
> not just yours.
> So there shouldn't be a need for this change now, right?

This patch is sufficient on the BCM283x family of devices, but a Fix
for a non-existent patch is clearly superfluous. The author of the
original patch can consider this as a hint about the kind of issues that
need to be considered before resubmitting.



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