Re: [PATCH v2] mmc: meson-gx: do not use memcpy_to/fromio for dram-access-quirk

[Ulf Hansson]

On Tue, 28 Sept 2021 at 09:37, Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
>
> The memory at the end of the controller only accepts 32bit read/write
> accesses, but the arm64 memcpy_to/fromio implementation only uses 64bit
> (which will be split into two 32bit access) and 8bit leading to incomplete
> copies to/from this memory when the buffer is not multiple of 8bytes.
>
> Add a local copy using writel/readl accesses to make sure we use the right
> memory access width.
>
> The switch to memcpy_to/fromio was done because of 285133040e6c
> ("arm64: Import latest memcpy()/memmove() implementation"), but using memcpy
> worked before since it mainly used 32bit memory acceses.
>
> Fixes: 103a5348c22c ("mmc: meson-gx: use memcpy_to/fromio for dram-access-quirk")
> Reported-by: Christian Hewitt <christianshewitt@xxxxxxxxx>
> Suggested-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Tested-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>

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

Kind regards
Uffe


> ---
> Changes since v1:
> - added sg pre-validation at meson_mmc_request and dropped checks in meson_mmc_copy_buffer
>
>  drivers/mmc/host/meson-gx-mmc.c | 73 ++++++++++++++++++++++++++-------
>  1 file changed, 59 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 3f28eb4d17fe..8f36536cb1b6 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -746,7 +746,7 @@ 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 */
> +/* local sg copy for dram_access_quirk */
>  static void meson_mmc_copy_buffer(struct meson_host *host, struct mmc_data *data,
>                                   size_t buflen, bool to_buffer)
>  {
> @@ -764,21 +764,27 @@ static void meson_mmc_copy_buffer(struct meson_host *host, struct mmc_data *data
>         sg_miter_start(&miter, sgl, nents, sg_flags);
>
>         while ((offset < buflen) && sg_miter_next(&miter)) {
> -               unsigned int len;
> +               unsigned int buf_offset = 0;
> +               unsigned int len, left;
> +               u32 *buf = miter.addr;
>
>                 len = min(miter.length, buflen - offset);
> +               left = len;
>
> -               /* 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);
> +               if (to_buffer) {
> +                       do {
> +                               writel(*buf++, host->bounce_iomem_buf + offset + buf_offset);
> +
> +                               buf_offset += 4;
> +                               left -= 4;
> +                       } while (left);
>                 } else {
> -                       if (to_buffer)
> -                               memcpy(host->bounce_buf + offset, miter.addr, len);
> -                       else
> -                               memcpy(miter.addr, host->bounce_buf + offset, len);
> +                       do {
> +                               *buf++ = readl(host->bounce_iomem_buf + offset + buf_offset);
> +
> +                               buf_offset += 4;
> +                               left -= 4;
> +                       } while (left);
>                 }
>
>                 offset += len;
> @@ -830,7 +836,11 @@ 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);
> -                       meson_mmc_copy_buffer(host, data, xfer_bytes, true);
> +                       if (host->dram_access_quirk)
> +                               meson_mmc_copy_buffer(host, data, xfer_bytes, true);
> +                       else
> +                               sg_copy_to_buffer(data->sg, data->sg_len,
> +                                                 host->bounce_buf, xfer_bytes);
>                         dma_wmb();
>                 }
>
> @@ -849,12 +859,43 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
>         writel(cmd->arg, host->regs + SD_EMMC_CMD_ARG);
>  }
>
> +static int meson_mmc_validate_dram_access(struct mmc_host *mmc, struct mmc_data *data)
> +{
> +       struct scatterlist *sg;
> +       int i;
> +
> +       /* Reject request if any element offset or size is not 32bit aligned */
> +       for_each_sg(data->sg, sg, data->sg_len, i) {
> +               if (!IS_ALIGNED(sg->offset, sizeof(u32)) ||
> +                   !IS_ALIGNED(sg->length, sizeof(u32))) {
> +                       dev_err(mmc_dev(mmc), "unaligned sg offset %u len %u\n",
> +                               data->sg->offset, data->sg->length);
> +                       return -EINVAL;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  static void meson_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
>  {
>         struct meson_host *host = mmc_priv(mmc);
>         bool needs_pre_post_req = mrq->data &&
>                         !(mrq->data->host_cookie & SD_EMMC_PRE_REQ_DONE);
>
> +       /*
> +        * The memory at the end of the controller used as bounce buffer for
> +        * the dram_access_quirk only accepts 32bit read/write access,
> +        * check the aligment and length of the data before starting the request.
> +        */
> +       if (host->dram_access_quirk && mrq->data) {
> +               mrq->cmd->error = meson_mmc_validate_dram_access(mmc, mrq->data);
> +               if (mrq->cmd->error) {
> +                       mmc_request_done(mmc, mrq);
> +                       return;
> +               }
> +       }
> +
>         if (needs_pre_post_req) {
>                 meson_mmc_get_transfer_mode(mmc, mrq);
>                 if (!meson_mmc_desc_chain_mode(mrq->data))
> @@ -999,7 +1040,11 @@ 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);
> -               meson_mmc_copy_buffer(host, data, xfer_bytes, false);
> +               if (host->dram_access_quirk)
> +                       meson_mmc_copy_buffer(host, data, xfer_bytes, false);
> +               else
> +                       sg_copy_from_buffer(data->sg, data->sg_len,
> +                                           host->bounce_buf, xfer_bytes);
>         }
>
>         next_cmd = meson_mmc_get_next_command(cmd);
> --
> 2.25.1
>