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

[Marek Szyprowski]

Hi

On 08.06.2021 17:33, Neil Armstrong wrote:
> It has been reported that usage of memcpy() to/from an iomem mapping is invalid,
> and and 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>
>
> [1] 285133040e6c ("arm64: Import latest memcpy()/memmove() implementation")
>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> ---
> Hi Ulf, Marek, Mark,
>
> I haven't tested the patch yet, but should fix issue reported at [2].

Works fine here and fixed the issue.

Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

> Neil
>
> [2] https://lore.kernel.org/r/acb244ad-0759-5a96-c659-5c23003d3dcd@xxxxxxxxxxx
>
>   drivers/mmc/host/meson-gx-mmc.c | 48 ++++++++++++++++++++++++++++++---
>   1 file changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index b8b771b643cc..89ff6038092d 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -742,6 +742,48 @@ 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;
> +	void *buf = host->bounce_buf;
> +	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(buf + offset, miter.addr, len);
> +			else
> +				memcpy_fromio(miter.addr, buf + offset, len);
> +		} else {
> +			if (to_buffer)
> +				memcpy(buf + offset, miter.addr, len);
> +			else
> +				memcpy(miter.addr, 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);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland