| Message ID | 20170410040400.5509-1-joel@jms.id.au |
|---|---|
| Headers | show |
| Series | drivers: serial: Aspeed VUART driver | expand |
On Mon, Apr 10, 2017 at 7:04 AM, Joel Stanley <joel@jms.id.au> wrote: > From: Jeremy Kerr <jk@ozlabs.org> > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 11, 2017 at 9:45 PM, Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Mon, Apr 10, 2017 at 7:04 AM, Joel Stanley <joel@jms.id.au> wrote: >> From: Jeremy Kerr <jk@ozlabs.org> >> >> 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. I have made these ordering changes you requested. > >> + 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. It's an of driver, and this function does exactly what we require. I have left it in for v4. Cheers, Joel -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html