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Date: Thu, 6 May 2010 11:44:44 +0100 From: Ian Abbott <abbotti@....co.uk> To: "nios2-dev@...c.et.ntust.edu.tw" <nios2-dev@...c.et.ntust.edu.tw> CC: "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>, "gregkh@...e.de" <gregkh@...e.de>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "alan@...rguk.ukuu.org.uk" <alan@...rguk.ukuu.org.uk> Subject: Re: [Nios2-dev] [PATCH 2/2] serial: Add driver for the Altera UART On Wed, 2010-05-05 at 09:35 +0100, Tobias Klauser wrote: > Add an UART driver for the UART component available as a SOPC (System on > Programmable Chip) component for Altera FPGAs. [...] > +static void altera_uart_start_tx(struct uart_port *port) > +{ > + struct altera_uart *pp = container_of(port, struct altera_uart, port); > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + pp->imr |= ALTERA_UART_CONTROL_TRDY_MSK; > + writel(pp->imr, port->membase + ALTERA_UART_CONTROL_REG); > + spin_unlock_irqrestore(&port->lock, flags); > +} > + > +static void altera_uart_stop_tx(struct uart_port *port) > +{ > + struct altera_uart *pp = container_of(port, struct altera_uart, port); > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + pp->imr &= ~ALTERA_UART_CONTROL_TRDY_MSK; > + writel(pp->imr, port->membase + ALTERA_UART_CONTROL_REG); > + spin_unlock_irqrestore(&port->lock, flags); > +} > + > +static void altera_uart_stop_rx(struct uart_port *port) > +{ > + struct altera_uart *pp = container_of(port, struct altera_uart, port); > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + pp->imr &= ~ALTERA_UART_CONTROL_RRDY_MSK; > + writel(pp->imr, port->membase + ALTERA_UART_CONTROL_REG); > + spin_unlock_irqrestore(&port->lock, flags); > +} Those four functions shouldn't grab port->lock because the caller in serial_core.c grabs it before calling them. > +static irqreturn_t altera_uart_interrupt(int irq, void *data) > +{ > + struct uart_port *port = data; > + struct altera_uart *pp = container_of(port, struct altera_uart, port); > + unsigned int isr; > + > + isr = readl(port->membase + ALTERA_UART_STATUS_REG) & pp->imr; > + if (isr & ALTERA_UART_STATUS_RRDY_MSK) > + altera_uart_rx_chars(pp); > + if (isr & ALTERA_UART_STATUS_TRDY_MSK) > + altera_uart_tx_chars(pp); > + return IRQ_RETVAL(isr); > +} Either the interrupt routine should grab port->lock (see equivalent function in altera_jtaguart.c for an example), or this could be done lower down in altera_uart_rx_chars() and altera_uart_tx_chars(). (It's less messing about to do it here in the interrupt routine though.) > +static void altera_uart_console_putc(struct console *co, const char c) > +{ > + struct uart_port *port = &(altera_uart_ports + co->index)->port; > + int i; > + > + for (i = 0; i < 0x10000; i++) { > + if (readl(port->membase + ALTERA_UART_STATUS_REG) & > + ALTERA_UART_STATUS_TRDY_MSK) > + break; > + } > + writel(c, port->membase + ALTERA_UART_TXDATA_REG); > + for (i = 0; i < 0x10000; i++) { > + if (readl(port->membase + ALTERA_UART_STATUS_REG) & > + ALTERA_UART_STATUS_TRDY_MSK) > + break; > + } > +} I'd suggest calling udelay(1) in each iteration of the loop. Perhaps the second loop is overkill. I was also going to suggest using the port->lock spin lock, but I'm not sure about the policy regarding that for console output (the 8250 driver console output doesn't use the spin lock for example). -- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@....co.uk> )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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