Messages in this thread | | | Date | Thu, 7 Jan 2021 20:16:04 +0200 | From | Cristian Ciocaltea <> | Subject | Re: [PATCH v2 1/1] tty: serial: owl: Add support for kernel debugger |
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Hi Greg,
Thank you for the review!
On Thu, Jan 07, 2021 at 04:20:55PM +0100, Greg Kroah-Hartman wrote: > On Tue, Jan 05, 2021 at 07:02:02PM +0200, Cristian Ciocaltea wrote: > > Implement 'poll_put_char' and 'poll_get_char' callbacks in struct > > 'owl_uart_ops' that enables OWL UART to be used for kernel debugging > > over serial line. > > > > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
[...]
> > + > > +static void owl_uart_poll_put_char(struct uart_port *port, unsigned char ch) > > +{ > > + while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU) > > + cpu_relax(); > > Unbounded loops? What could possibly go wrong? > > :( > > Please don't do that in the kernel, put a max bound on this.
I didn't realize the issue since I had encountered this pattern in many other serial drivers, as well: altera_uart, arc_uart, atmel_serial, etc.
> And are you _SURE_ that cpu_relax() is what you want to call here?
I'm thinking of replacing the loop with 'readl_poll_timeout_atomic()', if that would be a better approach.
Kind regards, Cristi
> thanks, > > greg k-h
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