On Mon, Apr 10, 2017 at 7:04 AM, Joel Stanley <joel@xxxxxxxxx> wrote:
> From: Jeremy Kerr <jk@xxxxxxxxxx>
>
> This change adds a driver for the 16550-based Aspeed virtual UART
> device. We use a similar process to the of_serial driver for device
> probe, but expose some VUART-specific functions through sysfs too.
>
> The VUART is two UART 'front ends' connected by their FIFO (no actual
> serial line in between). One is on the BMC side (management controller)
> and one is on the host CPU side.
>
> This driver is for the BMC side. The sysfs files allow the BMC
> userspace, which owns the system configuration policy, to specify at
> what IO port and interrupt number the host side will appear to the host
> on the Host <-> BMC LPC bus. It could be different on a different system
> (though most of them use 3f8/4).
>
> OpenPOWER host firmware doesn't like it when the host-side of the
> VUART's FIFO is not drained. This driver only disables host TX discard
> mode when the port is in use. We set the VUART enabled bit when we bind
> to the device, and clear it on unbind.
>
> We don't want to do this on open/release, as the host may be using this
> bit to configure serial output modes, which is independent of whether
> the devices has been opened by BMC userspace.
> +static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled)
> +{
> + u8 reg;
> +
> + reg = readb(vuart->regs + ASPEED_VUART_GCRA);
> + reg &= ~ASPEED_VUART_GCRA_VUART_EN;
> + if (enabled)
> + reg |= ASPEED_VUART_GCRA_VUART_EN;
Usually the pattern is
if (something)
set x bit;
else
clear x bit;
It would make it one operation in any case and a bit more understandable.
> + writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
> +}
> +
> +static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,
> + bool discard)
> +{
> + u8 reg;
> +
> + reg = readb(vuart->regs + ASPEED_VUART_GCRA);
> +
> + /* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */
> + reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
> + if (!discard)
> + reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;
Ditto.
> +
> + writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
> +}
> + /* The 8510 core creates the mapping, which we grab a reference to
> + * for VUART-specific registers */
Hmm... What about multi-line style?
> + port.port.irq = irq_of_parse_and_map(np, 0);
The benefit of use platform_get_irq() is to get rid of some OF specific headers.
--
With Best Regards,
Andy Shevchenko
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