linux-kernel - Re: [PATCH v2 16/28] spi: s3c64xx: simplify s3c64xx_wait_for

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Message-ID: <CAPLW+4mLWU-8H=qESe9csXm=e_ByvP=nc7MEJzknv+XAUjqUZg@mail.gmail.com>
Date: Thu, 25 Jan 2024 14:43:57 -0600
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: broonie@...nel.org, andi.shyti@...nel.org, arnd@...db.de, 
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, 
	alim.akhtar@...sung.com, linux-spi@...r.kernel.org, 
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-arch@...r.kernel.org, andre.draszik@...aro.org, 
	peter.griffin@...aro.org, kernel-team@...roid.com, willmcvicker@...gle.com
Subject: Re: [PATCH v2 16/28] spi: s3c64xx: simplify s3c64xx_wait_for_pio()

On Thu, Jan 25, 2024 at 8:50 AM Tudor Ambarus <tudor.ambarus@...aroorg> wrote:
>
> s3c64xx_spi_transfer_one() makes sure that for PIO the xfer->len is
> always smaller than the fifo size. Since we can't receive more that the
> FIFO size, droop the loop handling, the code becomes less misleading.

Drop (spelling)?

For the patch: how exactly it was tested to make sure there is no regression?

>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
>  drivers/spi/spi-s3c64xx.c | 75 +++++++++------------------------------
>  1 file changed, 17 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index d2dd28ff00c6..00a0878aeb80 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -485,26 +485,6 @@ static int s3c64xx_enable_datapath(struct s3c64xx_spi_driver_data *sdd,
>         return 0;
>  }
>
> -static u32 s3c64xx_spi_wait_for_timeout(struct s3c64xx_spi_driver_data *sdd,
> -                                       int timeout_ms)
> -{
> -       void __iomem *regs = sdd->regs;
> -       unsigned long val = 1;
> -       u32 status;
> -       u32 max_fifo = FIFO_DEPTH(sdd);
> -
> -       if (timeout_ms)
> -               val = msecs_to_loops(timeout_ms);
> -
> -       do {
> -               status = readl(regs + S3C64XX_SPI_STATUS);
> -       } while (FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status) < max_fifo &&
> -                --val);
> -
> -       /* return the actual received data length */
> -       return FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status);
> -}
> -
>  static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
>                                 struct spi_transfer *xfer)
>  {
> @@ -553,13 +533,11 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>                                 struct spi_transfer *xfer, bool use_irq)
>  {
>         void __iomem *regs = sdd->regs;
> +       u8 *buf = xfer->rx_buf;
> +       unsigned long time_us;
>         unsigned long val;
> -       u32 status;
> -       int loops;
> -       u32 cpy_len;
> -       u8 *buf;
> +       u32 status, len;
>         int ms;
> -       unsigned long time_us;
>
>         /* microsecs to xfer 'len' bytes @ 'cur_speed' */
>         time_us = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed;
> @@ -582,48 +560,29 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>                 status = readl(regs + S3C64XX_SPI_STATUS);
>         } while (FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status) < xfer->len &&
>                  --val);
> -
>         if (!val)
>                 return -EIO;
>
>         /* If it was only Tx */
> -       if (!xfer->rx_buf) {
> +       if (!buf) {
>                 sdd->state &= ~TXBUSY;
>                 return 0;
>         }
>
> -       /*
> -        * If the receive length is bigger than the controller fifo
> -        * size, calculate the loops and read the fifo as many times.
> -        * loops = length / max fifo size (calculated by using the
> -        * fifo mask).
> -        * For any size less than the fifo size the below code is
> -        * executed atleast once.
> -        */
> -       loops = xfer->len / FIFO_DEPTH(sdd);
> -       buf = xfer->rx_buf;
> -       do {
> -               /* wait for data to be received in the fifo */
> -               cpy_len = s3c64xx_spi_wait_for_timeout(sdd,
> -                                                      (loops ? ms : 0));
> -
> -               switch (sdd->cur_bpw) {
> -               case 32:
> -                       ioread32_rep(regs + S3C64XX_SPI_RX_DATA,
> -                                    buf, cpy_len / 4);
> -                       break;
> -               case 16:
> -                       ioread16_rep(regs + S3C64XX_SPI_RX_DATA,
> -                                    buf, cpy_len / 2);
> -                       break;
> -               default:
> -                       ioread8_rep(regs + S3C64XX_SPI_RX_DATA,
> -                                   buf, cpy_len);
> -                       break;
> -               }
> +       len = FIELD_GET(S3C64XX_SPI_ST_RX_FIFO_LVL, status);
> +
> +       switch (sdd->cur_bpw) {
> +       case 32:
> +               ioread32_rep(regs + S3C64XX_SPI_RX_DATA, buf, len / 4);
> +               break;
> +       case 16:
> +               ioread16_rep(regs + S3C64XX_SPI_RX_DATA, buf, len / 2);
> +               break;
> +       default:
> +               ioread8_rep(regs + S3C64XX_SPI_RX_DATA, buf, len);
> +               break;
> +       }
>
> -               buf = buf + cpy_len;
> -       } while (loops--);
>         sdd->state &= ~RXBUSY;
>
>         return 0;
> --
> 2.43.0.429.g432eaa2c6b-goog
>