[U-Boot] [PATCH 01/10] spi: sun4i: Poll for rxfifo empty

[André Przywara]

On Sat,  9 Feb 2019 18:44:51 +0530
Jagan Teki <jagan at amarulasolutions.com> wrote:

Hi,

> To drain rx fifo the fifo need to poll till the fifo
> count become empty.
> 
> The current code is using wait_for_bit logic on control
> register with exchange burst mode mask, which is not a
> proper way of waiting for draining fifo.
> 
> So, add code for polling fifo status register till rxfifo
> count become empty.
> 
> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
> ---
>  drivers/spi/sun4i_spi.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/spi/sun4i_spi.c b/drivers/spi/sun4i_spi.c
> index 38cc743c61..87b396a96e 100644
> --- a/drivers/spi/sun4i_spi.c
> +++ b/drivers/spi/sun4i_spi.c
> @@ -31,6 +31,8 @@
>  
>  #include <asm/arch/clock.h>
>  
> +#include <linux/iopoll.h>
> +
>  #define SUN4I_FIFO_DEPTH	64
>  
>  #define SUN4I_RXDATA_REG	0x00
> @@ -46,7 +48,6 @@
>  #define SUN4I_CTL_LMTF			BIT(6)
>  #define SUN4I_CTL_TF_RST		BIT(8)
>  #define SUN4I_CTL_RF_RST		BIT(9)
> -#define SUN4I_CTL_XCH_MASK		0x0400
>  #define SUN4I_CTL_XCH			BIT(10)
>  #define SUN4I_CTL_CS_MASK		0x3000
>  #define SUN4I_CTL_CS(cs)		(((cs) << 12) & SUN4I_CTL_CS_MASK)
> @@ -308,7 +309,7 @@ static int sun4i_spi_xfer(struct udevice *dev, unsigned int bitlen,
>  	struct dm_spi_slave_platdata *slave_plat = dev_get_parent_platdata(dev);
>  
>  	u32 len = bitlen / 8;
> -	u32 reg;
> +	u32 reg, rx_fifocnt;
>  	u8 nbytes;
>  	int ret;
>  
> @@ -343,10 +344,12 @@ static int sun4i_spi_xfer(struct udevice *dev, unsigned int bitlen,
>  		reg = readl(&priv->regs->ctl);
>  		writel(reg | SUN4I_CTL_XCH, &priv->regs->ctl);
>  
> -		/* Wait transfer to complete */
> -		ret = wait_for_bit_le32(&priv->regs->ctl, SUN4I_CTL_XCH_MASK,
> -					false, SUN4I_SPI_TIMEOUT_US, false);
> -		if (ret) {
> +		/* Wait till RX FIFO to be empty */
> +		ret = readl_poll_timeout(&priv->regs->ctl, rx_fifocnt,

That's not the right register, it should be regs->fifo_sta.

> +					 !(((rx_fifocnt & SUN4I_FIFO_STA_RF_CNT_MASK) >>
> +					 SUN4I_FIFO_STA_RF_CNT_BITS) < nbytes),

I think removing the negation and using ">=" instead is less confusing.

Cheers,
Andre.


> +					 SUN4I_SPI_TIMEOUT_US);
> +		if (ret < 0) {
>  			printf("ERROR: sun4i_spi: Timeout transferring data\n");
>  			sun4i_spi_set_cs(bus, slave_plat->cs, false);
>  			return ret;