On Wed, Sep 03, 2014 at 01:00:51PM +0100, Daniel Thompson wrote:
> The architectures where this peripheral exists (ARM and SH) have expensive
> implementations of writel(), reliant on spin locks and explicit L2 cache
> management. These architectures provide a cheaper writel_relaxed() which
> is much better suited to peripherals that do not perform DMA. The
> situation with readl()/readl_relaxed()is similar although less acute.
>
> This driver does not use DMA and will be more power efficient and more
> robust (due to absense of spin locks during console I/O) if it uses the
> relaxed variants.
>
> This change means the driver is no longer portable and therefore no
> longer suitable for compile testing.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxx>
> Cc: Patrice Chotard <patrice.chotard@xxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Jiri Slaby <jslaby@xxxxxxx>
> Cc: kernel@xxxxxxxxxxx
> Cc: linux-serial@xxxxxxxxxxxxxxx
> Acked-by: Maxime Coquelin <maxime.coquelin@xxxxxx>
> Acked-by: Peter Griffin <peter.griffin@xxxxxxxxxx>
> ---
> drivers/tty/serial/Kconfig | 2 +-
> drivers/tty/serial/st-asc.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 26cec64d..e9b1735 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1527,7 +1527,7 @@ config SERIAL_FSL_LPUART_CONSOLE
> config SERIAL_ST_ASC
> tristate "ST ASC serial port support"
> select SERIAL_CORE
> - depends on ARM || COMPILE_TEST
> + depends on ARM
I really don't like stuff that does this, sorry. I want to test build
as many drivers as I can. COMPILE_TEST does not mean that the driver is
"portable", only that it builds properly on all platforms.
> help
> This driver is for the on-chip Asychronous Serial Controller on
> STMicroelectronics STi SoCs.
> diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
> index 8b2d735..adadbc1 100644
> --- a/drivers/tty/serial/st-asc.c
> +++ b/drivers/tty/serial/st-asc.c
> @@ -151,12 +151,12 @@ static inline struct asc_port *to_asc_port(struct uart_port *port)
>
> static inline u32 asc_in(struct uart_port *port, u32 offset)
> {
> - return readl(port->membase + offset);
> + return readl_relaxed(port->membase + offset);
What plaforms do not provide readl_relaxed()?
thanks,
greg k-h
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