Date:	Mon, 15 Nov 2010 19:45:45 +0900
From:	"Tomoya MORINAGA" <tomoya-linux@....okisemi.com>
To:	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	"Alan Cox" <alan@...ux.intel.com>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	"Ben Dooks" <ben-linux@...ff.org>,
	"Kukjin Kim" <kgene.kim@...sung.com>,
	"Mike Frysinger" <vapier@...too.org>,
	"Feng Tang" <feng.tang@...el.com>,
	"Tobias Klauser" <tklauser@...tanz.ch>,
	"LKML" <linux-kernel@...r.kernel.org>, <yong.y.wang@...el.com>,
	<qi.wang@...el.com>, <kok.howg.ewe@...el.com>,
	<andrew.chih.howe.khor@...el.com>
Subject: Re: [PATCH v2] EG20T: Update PCH_UART driver to 2.6.36

On Friday, November 12, 2010 7:07 PM, Alan Cox wrote:

> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +
> +#ifdef CONFIG_PCH_DMA
> +#include <linux/dmaengine.h>
> +#include <linux/pch_dma.h>
> +#endif
> 
> You do not need this ifdef. Even if you are not using the DMA feature it
> will still compile. DMA/non-DMA needs to be runtime. See below
> 
> +enum {
> + PCH_UART_HAL_INVALID_PARAM = EINVAL,
> + PCH_UART_HAL_NOT_INITIALIZED = 256,
> + PCH_UART_HAL_NOT_REQUESTED,
> + PCH_UART_HAL_BASE_NOT_SET,
> + PCH_UART_HAL_INVALID_BAUD,
> + PCH_UART_HAL_INVALID_PARITY,
> + PCH_UART_HAL_INVALID_WLS,
> + PCH_UART_HAL_INVALID_FIFO_CLR,
> + PCH_UART_HAL_INVALID_DMAMODE,
> + PCH_UART_HAL_INVALID_FIFOSIZE,
> + PCH_UART_HAL_INVALID_TRIGGER,
> + PCH_UART_HAL_INVALID_STB,
> + PCH_UART_HAL_READ_ERROR,
> +};
> 
> These should be replaced with ordinary Linux error codes in the functions.

I agree.

> 
> +struct eg20t_port {
> + struct uart_port port;
> + int port_type;
> + void __iomem *membase;
> + resource_size_t mapbase;
> + unsigned int iobase;
> + struct pci_dev *pdev;
> + int fifo_size;
> + int base_baud;
> + int start_tx;
> + int start_rx;
> + int tx_empty;
> + int int_dis_flag;
> + int trigger;
> + int trigger_level;
> + struct pch_uart_buffer rxbuf;
> + unsigned int dmsr;
> + unsigned int fcr;
> +#ifdef CONFIG_PCH_DMA
> + struct dma_async_tx_descriptor *desc_tx;
> + struct dma_async_tx_descriptor *desc_rx;
> + struct pch_dma_slave param_tx;
> + struct pch_dma_slave param_rx;
> + struct dma_chan *chan_tx;
> + struct dma_chan *chan_rx;
> + struct scatterlist sg_tx;
> + struct scatterlist sg_rx;
> + int tx_dma_use;
> + void *rx_buf_virt;
> + dma_addr_t rx_buf_dma;
> +#endif
> +};
> 
> +static unsigned int get_msr(struct eg20t_port *priv, void __iomem *base)
> +{
> + unsigned int msr = ioread8(base + PCH_UART_MSR);
> + priv->dmsr |= msr & PCH_UART_MSR_DELTA;
> +
> + return msr;
> 
> msr should be a u8 ? Is there a reason priv->dmsr is unsigned int ?

There is no reason.
I will modify.

> 
> +static void pch_uart_hal_enable_interrupt(struct eg20t_port *priv,
> +   unsigned int flag)
> +{
> + unsigned int ier = ioread8(priv->membase + PCH_UART_IER);
> + ier |= flag & PCH_UART_IER_MASK;
> + iowrite8(ier, priv->membase + PCH_UART_IER);
> +}
> 
> Same for ier and fcr ?

I will modify.

> 
> +static int pch_uart_hal_read(struct eg20t_port *priv, unsigned char *buf,
> +      int rx_size)
> +{
> + int i;
> + unsigned int rbr, lsr;
> +
> + lsr = ioread8(priv->membase + PCH_UART_LSR);
> + for (i = 0, lsr = ioread8(priv->membase + PCH_UART_LSR);
> +      i < rx_size && lsr & PCH_UART_LSR_DR;
> +      lsr = ioread8(priv->membase + PCH_UART_LSR)) {
> + rbr = ioread8(priv->membase + PCH_UART_RBR);
> + buf[i++] = (unsigned char)rbr;
> + }
> 
> Same again here - which would also lose the cast

I will modify.

> 
> +static int pch_uart_hal_get_line_status(struct eg20t_port *priv)
> +{
> + unsigned int lsr;
> + int ret;
> +
> + lsr = ioread8(priv->membase + PCH_UART_LSR);
> + ret = (int)lsr;
> 
> And here

I will.

> 
> +static int push_rx(struct eg20t_port *priv, const unsigned char *buf,
> +    int size)
> +{
> + struct uart_port *port;
> + struct tty_struct *tty;
> + int sz, i, j;
> + int loop;
> + int pushed;
> +
> + port = &priv->port;
> + tty = tty_port_tty_get(&port->state->port);
> + if (!tty) {
> + pr_info("%s:tty is busy now", __func__);
> + return -EBUSY;
> + }
> 
> Don't log this. It is a perfectly normal situation - no pr_info needed
> (pr_debug if testing perhaps)

I agree.
I will modify.

> 
> +
> + for (pushed = 0, i = 0, loop = 1; (pushed < size) && loop;
> +      pushed += sz, i++) {
> + sz = tty_insert_flip_string(tty, &buf[pushed], size - pushed);
> + for (j = 0; (j < 100000) && (sz == 0); j++) {
> + tty_flip_buffer_push(tty);
> + sz = tty_insert_flip_string(tty, &buf[pushed],
> +     size - pushed);
> + }
> + if (sz == 0)
> + loop = 0;
> + }
> 
> This should not be needed. tty_insert_flip_string tries to insert as much as
> it can. Except when tty->low_latency is set, which requires the call is not
> from an interrupt handler the flip_buffer_push will queue data to the line
> discipline it will not make space.

I will delete the above (if (sz == 0) ~)


> 
> + room = tty_buffer_request_room(tty, size);
> +
> + if (room < size)
> + dev_warn(port->dev, "Rx overrun: dropping %u bytes\n",
> + size - room);
> + if (!room)
> + return room;
> +
> + for (i = 0; i < room; i++) {
> + tty_insert_flip_char(tty, ((u8 *)sg_virt(&priv->sg_rx))[i],
> +      TTY_NORMAL);
> + }
> 
> You can replace all of that with a single call to tty_insert_flip_string ?

I will replace.

> 
> + struct tty_struct *tty = tty_port_tty_get(&port->state->port);
> + if (!tty) {
> + pr_info("%s:tty is busy now", __func__);
> 
> Again don't log this.
> 
> +static void pch_uart_send_xchar(struct uart_port *port, char ch)
> +{
> +}
> 
> ??

I will delete.

> 
> + ret = pch_uart_hal_set_fifo(priv, PCH_UART_HAL_DMA_MODE0,
> +     fifo_size, priv->trigger);
> 
> Is this missing check intentional ?

I will add checking processing of returned value.

> +
> + ret = request_irq(priv->port.irq, pch_uart_interrupt, IRQF_SHARED,
> + KBUILD_MODNAME, priv);
> +
> + if (ret < 0)
> + return ret;
> 
> 
> +static int pch_uart_verify_port(struct uart_port *port,
> +                               struct serial_struct *serinfo)
> +{
> +       return 0;
> +}
> 
> 
> As you don't support low latency you want to do
> 
> static int pch_uart_verify_port(struct uart_port *port,
>                                struct serial_struct *serinfo)
> {
> if (serinfo->flags & UPF_LOW_LATENCY)
> return -EOPNOTSUPP;
> return 0;
> }
> 
> (A few other drivers also miss this)
> 
> 
> What you could also consider doing is
> 
> 
> static int pch_uart_verify_port(struct uart_port *port,
>                                struct serial_struct *serinfo)
> {
> if (serinfo->flags & UPF_LOW_LATENCY)
> use_pio_modes;
> /* Avoid tty->low_latency being set as we do not support it */
> serinfo->flags &= ~UPF_LOW_LATENCY;
> } else
> use_dma_modes;
> return 0;
> }
> 
> I think that would make "setserial /dev/ttyPCH0 low_latency" select PIO
> and the reverse "setserial /dev/ttyPCH0 ^low_latency" select DMA mode but it
> would need testing to make sure that it is all that is needed.

I will modify like above so that it can switch w/wo DMA dynamically.

I have a question.
Does our driver care CONFIG_PCH_DMA configuration ?

Thanks,

Tomoya MORINAGA
OKI SEMICONDUCTOR CO., LTD.
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