[PATCH v2] mmc: dw_mmc: Fix the DTO timeout overflow calculation for 32-bit systems

[Shawn Lin]

[+ Jaehoon]

On 2018/2/22 21:34, Evgeniy Didin wrote:
> In commit 9d9491a7da2a ("mmc: dw_mmc: Fix the DTO timeout calculation") have been made
> changes which cause multiply overflow for 32-bit systems.
> The broken timeout calculations caused false interrupt latency warnings
> and stacktrace splat (such as below) when accessing the SD Card.
> 
> | Running :  4M-check-reassembly-tcp-cmykw2-rotatew2.out -v0 -w1
> | -  Info: Finished target initialization.
> | mmcblk0: error -110 transferring data, sector 320544, nr 2048, cmd response
> |  0x900, card status 0x0
> | mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 400000Hz, actual
> | 396825HZ div = 63)
> | mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 25000000Hz, actual
> |  25000000HZ div = 1)
> | ------------[ cut here ]------------
> | softirq: huh, entered softirq 6 TASKLET 6f6a9412 with preempt_count 00000101,
> | exited with 00000100?
> | WARNING: CPU: 2 PID: 0 at ../lib/scatterlist.c:652 sg_miter_next+0x28/0x20c
> | Modules linked in:
> | CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.15.0 #57
> |
> | Stack Trace:
> |  arc_unwind_core.constprop.1+0xd0/0xf4
> |  dump_stack+0x68/0x80
> |  warn_slowpath_null+0x4e/0xec
> |  sg_miter_next+0x28/0x20c
> |  dw_mci_read_data_pio+0x44/0x190
> |  dw_mmc f000a000.mmc: Unexpected interrupt latency

I think we tested SD cards but the main reason we missed
this is that we don't use pio mode since dw_mmc decides
the transfer mode via HCON register but we don't have one
platform at hand then to do that. Given the data-transfer-over
interrupt should come after the data hit the RAM, so pio mode
could probably consume more time than IDMAC.

> |   dw_mci_interrupt+0x3ee/0x530
> |  __handle_irq_event_percpu+0x56/0x150
> |  handle_irq_event+0x34/0x78
> |  handle_level_irq+0x8e/0x120
> |  generic_handle_irq+0x1c/0x2c
> |  idu_cascade_isr+0x30/0x6c
> |  __handle_domain_irq+0x72/0xc8
> |  ret_from_exception+0x0/0x8
> |---[ end trace 2a58c9af6c25fe51 ]---
> 
> Lets cast this multiply to u64 type which prevents overflow.
> 
> Tested-by: Vineet Gupta <Vineet.Gupta1 at synopsys.com>
> Fixes: ARC STAR 9001306872 HSDK, sdio: board crashes when copying big files
> 
> Signed-off-by: Evgeniy Didin <Evgeniy.Didin at synopsys.com>
> 
> CC: Alexey Brodkin <abrodkin at synopsys.com>
> CC: Eugeniy Paltsev <paltsev at synopsys.com>
> CC: Douglas Anderson <dianders at chromium.org>
> CC: Ulf Hansson <ulf.hansson at linaro.org>
> CC: linux-kernel at vger.kernel.org
> CC: linux-snps-arc at lists.infradead.org
> Cc: <stable at vger.kernel.org> #  9d9491a7da2a mmc: dw_mmc: Fix the DTO timeout calculation

The fix looks good to me, but the tags should be improved a bit:

Fixes: 9d9491a7da2a ("mmc: dw_mmc: Fix the DTO timeout calculation")
Cc: <stable at vger.kernel.org>

Otherwise,
Reviewed-by: Shawn Lin <shawn.lin at rock-chips.com>

BTW, would you mind cooking another patch for fixing cto_ms case?


> ---
> Changes since v1:
> -uint64_t switched to u64
> -changed commit message
>   drivers/mmc/host/dw_mmc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 0aa39975f33b..1a0b9751c67c 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1944,7 +1944,7 @@ static void dw_mci_set_drto(struct dw_mci *host)
>   	drto_div = (mci_readl(host, CLKDIV) & 0xff) * 2;
>   	if (drto_div == 0)
>   		drto_div = 1;
> -	drto_ms = DIV_ROUND_UP(MSEC_PER_SEC * drto_clks * drto_div,
> +	drto_ms = DIV_ROUND_UP((u64)MSEC_PER_SEC * drto_clks * drto_div,
>   			       host->bus_hz);
>   
>   	/* add a bit spare time */
> 


-- 
Best Regards
Shawn Lin