On Tue, 6 Feb 2024 at 18:28, Ivan Semenov <ivan@xxxxxxxxxxx> wrote:
>
> The Linux mmc driver currently encounters a problem with eMMC chips connected via a 1-bit bus, when the chip supports a 4-bit bus. This regression was introduced in commit 577fb13 after functioning correctly in kernel version 3.15.
>
> In the function mmc_select_bus_width, the driver attempts to switch to 8-bit and 4-bit modes, but if the 4-bit bus test fails, it does not fall back to 1-bit mode and leaves eMMC in broken 4-bit mode. This results in I/O errors and failure to read the partition table.
>
> This patch addresses the issue by ensuring that the driver fallback to 1-bit bus mode if the attempt to switch to 4-bit mode fails.
>
> dmesg log for Samsung eMMC 5.1 chip connected via 1bit bus (only D0 pin) before patch:
Wow, that was an old bug you found there.
Just to make sure I understand correctly, the platform only supports
1-bit bus, but the DTS doesn't reflect that correctly as it instead
indicates that 4 and 8-bit modes are supported?
Don't get me wrong, I think the initialization-error-path should be
able to cope with that, so we should certainly fix it!
>
> [134509.044225] mmc0: switch to bus width 4 failed
> [134509.044509] mmc0: new high speed MMC card at address 0001
> [134509.054594] mmcblk0: mmc0:0001 BGUF4R 29.1 GiB
> [134509.281602] mmc0: switch to bus width 4 failed
> [134509.282638] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.282657] Buffer I/O error on dev mmcblk0, logical block 0, async page read
> [134509.284598] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.284602] Buffer I/O error on dev mmcblk0, logical block 0, async page read
> [134509.284609] ldm_validate_partition_table(): Disk read failed.
> [134509.286495] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.286500] Buffer I/O error on dev mmcblk0, logical block 0, async page read
> [134509.288303] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.288308] Buffer I/O error on dev mmcblk0, logical block 0, async page read
> [134509.289540] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.289544] Buffer I/O error on dev mmcblk0, logical block 0, async page read
> [134509.289553] mmcblk0: unable to read partition table
> [134509.289728] mmcblk0boot0: mmc0:0001 BGUF4R 31.9 MiB
> [134509.290283] mmcblk0boot1: mmc0:0001 BGUF4R 31.9 MiB
> [134509.294577] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
> [134509.295835] I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
> [134509.295841] Buffer I/O error on dev mmcblk0, logical block 0, async page read
>
> After patch:
>
> [134551.089613] mmc0: switch to bus width 4 failed
> [134551.090377] mmc0: new high speed MMC card at address 0001
> [134551.102271] mmcblk0: mmc0:0001 BGUF4R 29.1 GiB
> [134551.113365] mmcblk0: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12 p13 p14 p15 p16 p17 p18 p19 p20 p21
> [134551.114262] mmcblk0boot0: mmc0:0001 BGUF4R 31.9 MiB
> [134551.114925] mmcblk0boot1: mmc0:0001 BGUF4R 31.9 MiB
To allow me to apply the patch, you need to provide your
Signed-off-by-tag. According to the below:
Signed-off-by: Ivan Semenov <ivan@xxxxxxxxxxx>
Please tell me if you are okay with that, then I can amend the patch
when applying. No need for you to post a new version.
> ---
> drivers/mmc/core/mmc.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index f410bee50132..58ed7193a3ca 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1015,10 +1015,12 @@ static int mmc_select_bus_width(struct mmc_card *card)
> static unsigned ext_csd_bits[] = {
> EXT_CSD_BUS_WIDTH_8,
> EXT_CSD_BUS_WIDTH_4,
> + EXT_CSD_BUS_WIDTH_1,
> };
> static unsigned bus_widths[] = {
> MMC_BUS_WIDTH_8,
> MMC_BUS_WIDTH_4,
> + MMC_BUS_WIDTH_1,
> };
> struct mmc_host *host = card->host;
> unsigned idx, bus_width = 0;
For my understanding, does your platform support HS200 mode too? Or
only high-speed mode?
The reason for my question is that it would be interesting to
understand whether we end up running the error path in
mmc_select_hs200() or not.
[...]
Kind regards
Uffe
