On Thu, Mar 17, 2022 at 06:46:25PM +0100, 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.
...
> +#define DW_UART_TDMACR 0x10c /* DMA Control Register Transmit Mode */
> +#define DW_UART_RDMACR 0x110 /* DMA Control Register Receive Mode */
These are not Synposys ones.
...
> +static u32 dw8250_rzn1_get_dmacr_burst(int max_burst)
> +{
> + if (max_burst >= 8)
> + return DW_UART_xDMACR_8_WORD_BURST;
> + else if (max_burst >= 4)
> + return DW_UART_xDMACR_4_WORD_BURST;
> + else
> + return DW_UART_xDMACR_1_WORD_BURST;
> +}
Redundant 'else' in all cases.
--
With Best Regards,
Andy Shevchenko
