On Wed, Mar 30, 2022 at 03:20:36PM +0200, Miquel Raynal wrote:
> From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>
> DW based controllers like the one on Renesas RZ/N1 must be programmed as
> flow controllers when using DMA.
>
> * Table 11.45 of the system manual, "Flow Control Combinations", states
> that using UART with DMA requires setting the DMA in the peripheral
> flow controller mode regardless of the direction.
>
> * Chapter 11.6.1.3 of the system manual, "Basic Interface Definitions",
> explains that the burst size in the above case must be configured in
> the peripheral's register DEST/SRC_BURST_SIZE.
>
> Experiments shown that upon Rx timeout, the DMA transaction needed to be
> manually cleared as well.
One comment below, after addressing,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
> Co-developed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_dw.c | 64 +++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> index a156c6d2f866..977a473535e8 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -34,14 +34,26 @@
>
> /* Offsets for the DesignWare specific registers */
> #define DW_UART_USR 0x1f /* UART Status Register */
> +#define DW_UART_DMASA 0xa8 /* DMA Software Ack */
> +
> +#define RZN1_UART_TDMACR 0x10c /* DMA Control Register Transmit Mode */
> +#define RZN1_UART_RDMACR 0x110 /* DMA Control Register Receive Mode */
>
> /* DesignWare specific register fields */
> #define DW_UART_MCR_SIRE BIT(6)
>
> +/* Renesas specific register fields */
> +#define RZN1_UART_xDMACR_DMA_EN BIT(0)
> +#define RZN1_UART_xDMACR_1_WORD_BURST (0 << 1)
> +#define RZN1_UART_xDMACR_4_WORD_BURST (1 << 1)
> +#define RZN1_UART_xDMACR_8_WORD_BURST (3 << 1)
> +#define RZN1_UART_xDMACR_BLK_SZ(x) ((x) << 3)
> +
> /* Quirks */
> #define DW_UART_QUIRK_OCTEON BIT(0)
> #define DW_UART_QUIRK_ARMADA_38X BIT(1)
> #define DW_UART_QUIRK_SKIP_SET_RATE BIT(2)
> +#define DW_UART_QUIRK_IS_DMA_FC BIT(3)
>
> static inline struct dw8250_data *clk_to_dw8250_data(struct notifier_block *nb)
> {
> @@ -224,6 +236,7 @@ static int dw8250_handle_irq(struct uart_port *p)
> struct dw8250_data *d = to_dw8250_data(p->private_data);
> unsigned int iir = p->serial_in(p, UART_IIR);
> bool rx_timeout = (iir & 0x3f) == UART_IIR_RX_TIMEOUT;
> + unsigned int quirks = d->pdata->quirks;
> unsigned int status;
> unsigned long flags;
>
> @@ -247,6 +260,15 @@ static int dw8250_handle_irq(struct uart_port *p)
> spin_unlock_irqrestore(&p->lock, flags);
> }
>
> + /* Manually stop the Rx DMA transfer when acting as flow controller */
> + if (up->dma && up->dma->rx_running && rx_timeout && quirks & DW_UART_QUIRK_IS_DMA_FC) {
> + status = p->serial_in(p, UART_LSR);
> + if (status & (UART_LSR_DR | UART_LSR_BI)) {
> + writel(0, p->membase + RZN1_UART_RDMACR);
> + writel(1, p->membase + DW_UART_DMASA);
> + }
> + }
> +
> if (serial8250_handle_irq(p, iir))
> return 1;
>
> @@ -370,6 +392,42 @@ static bool dw8250_idma_filter(struct dma_chan *chan, void *param)
> return param == chan->device->dev;
> }
>
> +static u32 dw8250_rzn1_get_dmacr_burst(int max_burst)
> +{
> + if (max_burst >= 8)
> + return RZN1_UART_xDMACR_8_WORD_BURST;
> + else if (max_burst >= 4)
> + return RZN1_UART_xDMACR_4_WORD_BURST;
> + else
> + return RZN1_UART_xDMACR_1_WORD_BURST;
> +}
> +
> +static void dw8250_prepare_tx_dma(struct uart_8250_port *p)
> +{
> + struct uart_port *up = &p->port;
> + struct uart_8250_dma *dma = p->dma;
> + u32 val;
> +
> + writel(0, up->membase + RZN1_UART_TDMACR);
> + val = dw8250_rzn1_get_dmacr_burst(dma->txconf.dst_maxburst) |
> + RZN1_UART_xDMACR_BLK_SZ(dma->tx_size) |
> + RZN1_UART_xDMACR_DMA_EN;
> + writel(val, up->membase + RZN1_UART_TDMACR);
> +}
> +
> +static void dw8250_prepare_rx_dma(struct uart_8250_port *p)
> +{
> + struct uart_port *up = &p->port;
> + struct uart_8250_dma *dma = p->dma;
> + u32 val;
> +
> + writel(0, up->membase + RZN1_UART_RDMACR);
> + val = dw8250_rzn1_get_dmacr_burst(dma->rxconf.src_maxburst) |
> + RZN1_UART_xDMACR_BLK_SZ(dma->rx_size) |
> + RZN1_UART_xDMACR_DMA_EN;
> + writel(val, up->membase + RZN1_UART_RDMACR);
> +}
> +
> static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
> {
> struct device_node *np = p->dev->of_node;
> @@ -403,6 +461,12 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
> p->serial_out = dw8250_serial_out38x;
> if (quirks & DW_UART_QUIRK_SKIP_SET_RATE)
> p->set_termios = dw8250_do_set_termios;
> + if (quirks & DW_UART_QUIRK_IS_DMA_FC) {
> + data->data.dma.txconf.device_fc = 1;
> + data->data.dma.rxconf.device_fc = 1;
> + data->data.dma.prepare_tx_dma = dw8250_prepare_tx_dma;
> + data->data.dma.prepare_rx_dma = dw8250_prepare_rx_dma;
> + }
>
> } else if (acpi_dev_present("APMC0D08", NULL, -1)) {
> p->iotype = UPIO_MEM32;
> --
> 2.27.0
>
--
With Best Regards,
Andy Shevchenko
