linux-kernel - Re: [PATCH] spi: fsi: Remove multiple sequenced ops for restricted chips

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Message-ID: <CACPK8XeO7Oan+xBwOJ6VUfEF_gMs=NJ=rvVZjrFXczb4-YtCdA@mail.gmail.com>
Date:   Thu, 25 Mar 2021 02:20:16 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-spi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] spi: fsi: Remove multiple sequenced ops for restricted chips

On Wed, 24 Mar 2021 at 22:05, Eddie James <eajames@...ux.ibm.com> wrote:
>
> Updated restricted chips have trouble processing multiple sequenced
> operations. So remove the capability to sequence multiple operations and
> reduce the maximum transfer size to 8 bytes.
>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>

Reviewed-by: Joel Stanley <joel@....id.au>

> ---
>  drivers/spi/spi-fsi.c | 27 +++++++--------------------
>  1 file changed, 7 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
> index 3920cd3286d8..de359718e816 100644
> --- a/drivers/spi/spi-fsi.c
> +++ b/drivers/spi/spi-fsi.c
> @@ -26,7 +26,7 @@
>  #define SPI_FSI_BASE                   0x70000
>  #define SPI_FSI_INIT_TIMEOUT_MS                1000
>  #define SPI_FSI_MAX_XFR_SIZE           2048
> -#define SPI_FSI_MAX_XFR_SIZE_RESTRICTED        32
> +#define SPI_FSI_MAX_XFR_SIZE_RESTRICTED        8
>
>  #define SPI_FSI_ERROR                  0x0
>  #define SPI_FSI_COUNTER_CFG            0x1
> @@ -265,14 +265,12 @@ static int fsi_spi_sequence_transfer(struct fsi_spi *ctx,
>                                      struct fsi_spi_sequence *seq,
>                                      struct spi_transfer *transfer)
>  {
> -       bool docfg = false;
>         int loops;
>         int idx;
>         int rc;
>         u8 val = 0;
>         u8 len = min(transfer->len, 8U);
>         u8 rem = transfer->len % len;
> -       u64 cfg = 0ULL;
>
>         loops = transfer->len / len;
>
> @@ -292,28 +290,17 @@ static int fsi_spi_sequence_transfer(struct fsi_spi *ctx,
>                 return -EINVAL;
>         }
>
> -       if (ctx->restricted) {
> -               const int eidx = rem ? 5 : 6;
> -
> -               while (loops > 1 && idx <= eidx) {
> -                       idx = fsi_spi_sequence_add(seq, val);
> -                       loops--;
> -                       docfg = true;
> -               }
> -
> -               if (loops > 1) {
> -                       dev_warn(ctx->dev, "No sequencer slots; aborting.\n");
> -                       return -EINVAL;
> -               }
> +       if (ctx->restricted && loops > 1) {
> +               dev_warn(ctx->dev,
> +                        "Transfer too large; no branches permitted.\n");
> +               return -EINVAL;
>         }
>
>         if (loops > 1) {
> +               u64 cfg = SPI_FSI_COUNTER_CFG_LOOPS(loops - 1);
> +
>                 fsi_spi_sequence_add(seq, SPI_FSI_SEQUENCE_BRANCH(idx));
> -               docfg = true;
> -       }
>
> -       if (docfg) {
> -               cfg = SPI_FSI_COUNTER_CFG_LOOPS(loops - 1);
>                 if (transfer->rx_buf)
>                         cfg |= SPI_FSI_COUNTER_CFG_N2_RX |
>                                 SPI_FSI_COUNTER_CFG_N2_TX |
> --
> 2.27.0
>