Re: [PATCH v2 1/1] omap: serial: fix non-empty uart fifo read abort

[Kevin Hilman <khilman@deeprootsystems.com>]

Vikram Pandita <vikram.pandita@ti.com> writes:

> OMAP3630 and OMAP4430 UART IP blocks have a restriction wrt RX FIFO.
> Empty RX fifo read causes an abort. OMAP1/2/3 do not have this restriction.
>
> Overrigt the default 8250 read handler: mem_serial_in()
> by a custom handler: serial_in_8250()
>
> serial_in_8250() makes sure that RX fifo is not read when empty,
> on omap4 and 3630 silicons only
>
> tested on zoom3(3630) board
>
> Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
> ---
> v1: initial implementation
> 	http://patchwork.kernel.org/patch/60785/
> 	http://patchwork.kernel.org/patch/60786/
>
> v2: incorporate review comments from Alan Cox
> 	http://patchwork.kernel.org/patch/60785/
> 	No 8250 driver change required now
>
>  arch/arm/mach-omap2/serial.c |   28 ++++++++++++++++++++++++++++
>  1 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
> index 2e17b57..362cb82 100644
> --- a/arch/arm/mach-omap2/serial.c
> +++ b/arch/arm/mach-omap2/serial.c
> @@ -71,6 +71,30 @@ struct omap_uart_state {
>  
>  static LIST_HEAD(uart_list);
>  
> +static struct omap_uart_state omap_uart[];
> +static inline unsigned int serial_read_reg(struct plat_serial8250_port *, int);
> +
> +/*
> + * Overrigt the default 8250 read handler: mem_serial_in()
> + * Empty RX fifo read causes an abort on omap3630 and omap4
> + * This function makes sure that an empty rx fifo is not read on these silicons
> + * (OMAP1/2/3 are not affected)
> + */
> +static unsigned int serial_in_8250(struct uart_port *up, int offset)
> +{
> +	/* Do not read empty UART fifo on omap3630/44xx */
> +	if ((UART_RX == offset) &&
> +		(cpu_is_omap3630() || cpu_is_omap44xx())) {

Rather than the cpu_is_* here, why not just override the function 
for these platforms and leave the default for 34xx/35xx.

Kevin