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

[Neil Armstrong]

Hi,

On 08/06/2021 17:50, Marek Szyprowski wrote:
> 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>

Thanks, I'll need to rework to pass an __iomem pointer to memcpy_to/fromio so sparse doesn't scream anymore.

Neil

> 
>> 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
>