Hi Jiri, Thanks for the feedback. > Subject: Re: [PATCH] serial: 8250: dw: Fix the macro > RZN1_UART_xDMACR_8_WORD_BURST > > On 30. 06. 22, 10:39, Biju Das wrote: > > As per RZ/N1 peripheral user > > manual(r01uh0752ej0100-rzn1-peripheral.pdf) > > rev 1.0.0 Mar,2019, > > Is this public anywhere? Yes, It is available here[1] see page 72 and 73. [1] https://www.renesas.com/us/en/document/mah/rzn1d-group-rzn1s-group-rzn1l-group-users-manual-peripherals?language=en&r=1054561 > > > the value for 8_WORD_BURST is 4(b2,b1=2’b10). > > > > This patch fixes the macro as per the user manual. > > I'm curious, is the bottom bit from "3" ignored by the HW or does this > fix a real problem in behavior? Stating that might help backporters to > decide if to take the patch or not. See page 72 and 73. Yes, it fixes a real problem as by using a value of 8 , you are wrongly configuring DMA_BURST_SIZE of 1 instead of DMA_BURST_SIZE of 8. b2, b1 bUart_DEST_BURST _SIZE DEST_BURST_SIZE Destination Burst Transaction Size in Transmit FIFO. UART is the flow controller. Thus, the user must write this field before or at the same time the DMA mode is enabled. Number of data byte, to be written to the Transmit FIFO every time a transmit burst transaction request are made on DMA request. 2’b00 = 1 byte 2’b01 = 4 bytes 2’b10 = 8 bytes 2’b11 = Reserved, not used Cheers, Biju > > > Fixes: aa63d786cea2 ("serial: 8250: dw: Add support for DMA flow > > controlling devices") > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> > > --- > > drivers/tty/serial/8250/8250_dw.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/8250/8250_dw.c > > b/drivers/tty/serial/8250/8250_dw.c > > index f57bbd32ef11..931490b27d6b 100644 > > --- a/drivers/tty/serial/8250/8250_dw.c > > +++ b/drivers/tty/serial/8250/8250_dw.c > > @@ -47,7 +47,7 @@ > > #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_8_WORD_BURST (2 << 1) > > #define RZN1_UART_xDMACR_BLK_SZ(x) ((x) << 3) > > > > /* Quirks */ > > thanks, > -- > js
