Re: WinLink E850-96: WARNING: at block/blk-settings.c:204 blk_validate_limits

On Thu, Feb 29, 2024 at 8:56 AM Arnd Bergmann arnd@arndb.de wrote:

On Thu, Feb 29, 2024, at 15:14, Naresh Kamboju wrote:

...

The arm64 WinLink E850-96 Board boot failed with 16K and 64K page size builds Please find the below warning log on Linux next-20240229. First noticed on the next-20240220 tag.

This issue arises only when one of these Kconfig options is enabled. CONFIG_ARM64_16K_PAGES=y CONFIG_ARM64_64K_PAGES=y

Reported-by: Linux Kernel Functional Testing lkft@linaro.org

Warning log:

[ 2.231008] mmc_host mmc0: Bus speed (slot 0) = 49968750Hz (slot req 52000000Hz, actual 49968750HZ div = 0) [ 2.231714] mmc_host mmc0: Bus speed (slot 0) = 399750000Hz (slot req 200000000Hz, actual 199875000HZ div = 1) [ 2.241961] mmc0: new HS400 Enhanced strobe MMC card at address 0001 [ 2.249182] ------------[ cut here ]------------ [ 2.252371] WARNING: CPU: 3 PID: 90 at block/blk-settings.c:204 blk_validate_limits (block/blk-settings.c:204 (discriminator 1))

The warning was added with commit d690cb8ae14b ("block: add an API to atomically update queue limits")

•           if (!lim->max_segment_size)
  

•                   lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
  

•           if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
  

•                   return -EINVAL;
  
  

Whereas mmc_alloc_disk sets the limit as

    /*
     * Setting a virt_boundary implicity sets a max_segment_size, so try
     * to set the hardware one here.
     */
    if (host->can_dma_map_merge) {
            lim.virt_boundary_mask = dma_get_merge_boundary(mmc_dev(host));
            lim.max_segments = MMC_DMA_MAP_MERGE_SEGMENTS;
    } else {
            lim.max_segment_size =
                    round_down(host->max_seg_size, lim.logical_block_size);
            lim.max_segments = host->max_segs;
    }

and max_seg_size gets initialized to either one less than 64k, or to exactly 4k in the dwmmc driver here:

    /* Useful defaults if platform data is unset. */
    if (host->use_dma == TRANS_MODE_IDMAC) {
            mmc->max_segs = host->ring_size;
            mmc->max_blk_size = 65535;

Changing this value here to PAGE_SIZE (instead of 65535) makes E850-96 functional again (tested with CONFIG_ARM64_16K_PAGES=y). I'm sure this is just a quick hack, but maybe it can be helpful in further analysis. If anybody wants me to run some tests on E850-96 -- please let me know.

[snip]