[U-Boot] [PATCH] mx6: fsl_esdhc: Fix waiting for DMA operation completion

From: Dirk Behme <dirk.behme@gmail.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH] mx6: fsl_esdhc: Fix waiting for DMA operation completion
Date: Tue, 02 Apr 2013 20:10:47 +0200	[thread overview]
Message-ID: <515B1F27.4010702@gmail.com> (raw)
In-Reply-To: <515AFE1E.801@boundarydevices.com>

Am 02.04.2013 17:49, schrieb Eric Nelson:
> Thanks Andrew,
>
> On 04/02/2013 03:04 AM, Andrew Gabbasov wrote:
>> On iMX6 sometimes the Transfer Complete interrupt occurs earlier
>> than the DMA part completes its operation. If immediately after that
>> the read data is used for some data verification, those obtained data
>> may be incomplete, which causes intermittent verification failures.
>>
>
> Can you describe how to repeat this?
>
>> For example, when the default environment command tries to load and run
>> boot script from FAT partition on SD/MMC card, it sometimes fails,
>> reporting invalid partition table, or unknown partition type, or
>> something else of that kind. Such errors disappear if the build
>> configuration has CONFIG_SYS_FSL_ESDHC_USE_PIO, or if some delay
>> is added after transfer completion.
>>
> We do this on every boot on SABRE Lite and Nitrogen6x boards,
> and haven't seen an issue.
>
> What board are you testing on?
>
> Do you have cache enabled?
>
> Is this with an SD card or eMMC?

Andrew will have the details, but to my understanding this implements 
in U-Boot what the Freescale kernel has in

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/mmc/host/sdhci-esdhc-imx.c?h=imx_3.0.35_12.09.01#n234

for TO 1.0.

Best regards

Dirk

>> Adding extra waiting for DMA completion after Transfer Complete
>> event fixes this issue.
>>
>> Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
>> ---
>>   drivers/mmc/fsl_esdhc.c |    6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
>> index d2a505e..806c6dd 100644
>> --- a/drivers/mmc/fsl_esdhc.c
>> +++ b/drivers/mmc/fsl_esdhc.c
>> @@ -402,6 +402,12 @@ esdhc_send_cmd(struct mmc *mmc, struct mmc_cmd
>> *cmd, struct mmc_data *data)
>>                   return COMM_ERR;
>>           } while (!(irqstat & IRQSTAT_TC) &&
>>                   (esdhc_read32(&regs->prsstat) & PRSSTAT_DLA));
>> +#ifdef CONFIG_MX6
>> +        /* In imx6 TC (data end) interrupt sometimes occur earlier
>> +           than DMA completes. In this case just wait a little
>> more. */
>> +        while (!(irqstat & (IRQSTAT_DINT | IRQSTAT_DMAE)))
>> +            irqstat = esdhc_read32(&regs->irqstat);
>> +#endif
>>   #endif
>>       }
>>
>>
>
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