> On Feb 13, 2024, at 18:40, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> 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?
Yes, you are correct, and the second case - with no DTS, when emmc is
connected to PC via cardreader, but via 1bit connection only
>
> 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.
I’m ok with that, is it ok to put it here or I need to send a patch again?
Signed-off-by: Ivan Semenov <ivan@xxxxxxxxxxx>
>
>> ---
>> 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.
In my case, platform supports only High-Speed mode, so I can’t test in
with HS200 mode.
>
> [...]
>
> Kind regards
> Uffe
