On 25/10/2021 11:59, Bough Chen wrote:
> Hi Ulf, Adrian
>
> For mmc controllers with quirks SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC, it
> limit the max segment size as 64K-1.
> Currently, linux kernel support 4K/16K/64K PAGE_SIZE. If choose 64K
> PAGE_SIZE, sdhci in ADMA mode with the upper quirks will meet issue.
> Though mmc driver give block layer the max segment size through
> blk_queue_max_segment_size(), but in this function, it will compare the
> argument with PAGE_SIZE.
> In this case, finally the mmc request queue will get 64K as the max segment
> size. Once the sg data length=64K, ADMA will meet issue.
>
> Find this issue on i.MX8MM-evk board, and I just notice omap/tegra/s3c also
> contain this quirks, seems a common issue.
> Should sdhci driver detect this case, and change to use SDMA mode
> automatically? Any thoughts?
It seems sensible to clear SDHCI_USE_ADMA in sdhci_setup_host() if it is
not going to work because of >= 64K page size.
>
>
> /block/blk-settings.c
> void blk_queue_max_segment_size(struct request_queue *q, unsigned int
> max_size)
> {
> if (max_size < PAGE_SIZE) {
> max_size = PAGE_SIZE;
> printk(KERN_INFO "%s: set to minimum %d\n",
> __func__, max_size);
> }
>
> /* see blk_queue_virt_boundary() for the explanation */
> WARN_ON_ONCE(q->limits.virt_boundary_mask);
>
> q->limits.max_segment_size = max_size;
> }
> EXPORT_SYMBOL(blk_queue_max_segment_size);
>
>
>
> Best Regards
> Haibo Chen
>
>
