Re: [PATCH] mmc: meson-gx: use memcpy_to/fromio for dram-access-quirk

[Ulf Hansson]

On Wed, 9 Jun 2021 at 17:02, Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
>
> It has been reported that usage of memcpy() to/from an iomem mapping is invalid,
> and a recent arm64 memcpy update [1] triggers a memory abort when dram-access-quirk
> is used on the G12A/G12B platforms.
>
> This adds a local sg_copy_to_buffer which makes usage of io versions of memcpy
> when dram-access-quirk is enabled.
>
> Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
> Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> [1] 285133040e6c ("arm64: Import latest memcpy()/memmove() implementation")

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe

> ---
>  drivers/mmc/host/meson-gx-mmc.c | 50 +++++++++++++++++++++++++++++----
>  1 file changed, 45 insertions(+), 5 deletions(-)
>
>
> Changes since RFC:
> - moved iomem address to bounce_iomem_buf otherwise sparse screamed when feeding memcpy_to/fromio with non iomem pointer
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index b8b771b643cc..3e9b28f18c70 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -165,6 +165,7 @@ struct meson_host {
>
>         unsigned int bounce_buf_size;
>         void *bounce_buf;
> +       void __iomem *bounce_iomem_buf;
>         dma_addr_t bounce_dma_addr;
>         struct sd_emmc_desc *descs;
>         dma_addr_t descs_dma_addr;
> @@ -742,6 +743,47 @@ static void meson_mmc_desc_chain_transfer(struct mmc_host *mmc, u32 cmd_cfg)
>         writel(start, host->regs + SD_EMMC_START);
>  }
>
> +/* local sg copy to buffer version with _to/fromio usage for dram_access_quirk */
> +static void meson_mmc_copy_buffer(struct meson_host *host, struct mmc_data *data,
> +                                 size_t buflen, bool to_buffer)
> +{
> +       unsigned int sg_flags = SG_MITER_ATOMIC;
> +       struct scatterlist *sgl = data->sg;
> +       unsigned int nents = data->sg_len;
> +       struct sg_mapping_iter miter;
> +       unsigned int offset = 0;
> +
> +       if (to_buffer)
> +               sg_flags |= SG_MITER_FROM_SG;
> +       else
> +               sg_flags |= SG_MITER_TO_SG;
> +
> +       sg_miter_start(&miter, sgl, nents, sg_flags);
> +
> +       while ((offset < buflen) && sg_miter_next(&miter)) {
> +               unsigned int len;
> +
> +               len = min(miter.length, buflen - offset);
> +
> +               /* When dram_access_quirk, the bounce buffer is a iomem mapping */
> +               if (host->dram_access_quirk) {
> +                       if (to_buffer)
> +                               memcpy_toio(host->bounce_iomem_buf + offset, miter.addr, len);
> +                       else
> +                               memcpy_fromio(miter.addr, host->bounce_iomem_buf + offset, len);
> +               } else {
> +                       if (to_buffer)
> +                               memcpy(host->bounce_buf + offset, miter.addr, len);
> +                       else
> +                               memcpy(miter.addr, host->bounce_buf + offset, len);
> +               }
> +
> +               offset += len;
> +       }
> +
> +       sg_miter_stop(&miter);
> +}
> +
>  static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>  {
>         struct meson_host *host = mmc_priv(mmc);
> @@ -785,8 +827,7 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>                 if (data->flags & MMC_DATA_WRITE) {
>                         cmd_cfg |= CMD_CFG_DATA_WR;
>                         WARN_ON(xfer_bytes > host->bounce_buf_size);
> -                       sg_copy_to_buffer(data->sg, data->sg_len,
> -                                         host->bounce_buf, xfer_bytes);
> +                       meson_mmc_copy_buffer(host, data, xfer_bytes, true);
>                         dma_wmb();
>                 }
>
> @@ -955,8 +996,7 @@ static irqreturn_t meson_mmc_irq_thread(int irq, void *dev_id)
>         if (meson_mmc_bounce_buf_read(data)) {
>                 xfer_bytes = data->blksz * data->blocks;
>                 WARN_ON(xfer_bytes > host->bounce_buf_size);
> -               sg_copy_from_buffer(data->sg, data->sg_len,
> -                                   host->bounce_buf, xfer_bytes);
> +               meson_mmc_copy_buffer(host, data, xfer_bytes, false);
>         }
>
>         next_cmd = meson_mmc_get_next_command(cmd);
> @@ -1176,7 +1216,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
>                  * instead of the DDR memory
>                  */
>                 host->bounce_buf_size = SD_EMMC_SRAM_DATA_BUF_LEN;
> -               host->bounce_buf = host->regs + SD_EMMC_SRAM_DATA_BUF_OFF;
> +               host->bounce_iomem_buf = host->regs + SD_EMMC_SRAM_DATA_BUF_OFF;
>                 host->bounce_dma_addr = res->start + SD_EMMC_SRAM_DATA_BUF_OFF;
>         } else {
>                 /* data bounce buffer */
> --
> 2.25.1
>