Jaehoon,
On Fri, Mar 13, 2015 at 4:19 AM, Jaehoon Chung <jh80.ch...@samsung.com> wrote:
> Hi Doug.
>
> This patch is a right process. Just i wonder something.
>
> On 03/10/2015 08:18 AM, Doug Anderson wrote:
>> In the Designware databook's description of the "Voltage Switch Normal
>> Scenario" it instructs us to set a timer and fail the voltage change
>> if we don't see the voltage change interrupt within 2ms. Let's
>> implement that. Without implementing this I have often been able to
>> reproduce a hang while trying to send CMD11 on an rk3288-based board
>> while constantly ejecting and inserting UHS cards.
>>
>> Signed-off-by: Doug Anderson <diand...@chromium.org>
>> ---
>> drivers/mmc/host/dw_mmc.c | 26 ++++++++++++++++++++++++++
>> include/linux/mmc/dw_mmc.h | 2 ++
>> 2 files changed, 28 insertions(+)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 47dfd0e..d259662 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -1020,6 +1020,15 @@ static void __dw_mci_start_request(struct dw_mci
>> *host,
>>
>> dw_mci_start_command(host, cmd, cmdflags);
>>
>> + if (cmd->opcode == SD_SWITCH_VOLTAGE) {
>> + /*
>> + * Databook says to fail after 2ms w/ no response; give an
>> + * extra jiffy just in case we're about to roll over.
>> + */
>> + mod_timer(&host->cmd11_timer,
>> + jiffies + msecs_to_jiffies(2) + 1);
>
> What's "plus one"?
I tried to briefly describe it in the comment above with the "in case
we're about to roll over". ...but more detail...
* I expect HZ to be something like 100. ...so a jiffy will be 10ms.
2ms will be rounded up to 1 jiffy.
* It's entirely possible that we're about to roll over jiffies. That
is, we might make the mod_timer call when we're 1 nanosecond away from
moving from 999 to 1000 jiffies. We'll still read "jiffies" as 999
and add "msecs_to_jiffies(2)" to get 1000 jiffies. ...but then it
will roll over and we'll make the call mod_timer(1000) when jiffies is
already 1000. That means that we really got a 1ns delay--not so good.
...if we add the extra 1 jiffy then we'll probably really delay for
10-20ms, but that should be fine in this case.
If I misunderstood the above, please correct me.
>> + }
>> +
>> if (mrq->stop)
>> host->stop_cmdr = dw_mci_prepare_command(slot->mmc, mrq->stop);
>> else
>> @@ -2158,6 +2167,8 @@ static irqreturn_t dw_mci_interrupt(int irq, void
>> *dev_id)
>> /* Check volt switch first, since it can look like an error */
>> if ((host->state == STATE_SENDING_CMD11) &&
>> (pending & SDMMC_INT_VOLT_SWITCH)) {
>> + del_timer(&host->cmd11_timer);
>> +
>> mci_writel(host, RINTSTS, SDMMC_INT_VOLT_SWITCH);
>> pending &= ~SDMMC_INT_VOLT_SWITCH;
>> dw_mci_cmd_interrupt(host, pending);
>> @@ -2571,6 +2582,18 @@ ciu_out:
>> return ret;
>> }
>>
>> +static void dw_mci_cmd11_timer(unsigned long arg)
>> +{
>> + struct dw_mci *host = (struct dw_mci *)arg;
>> +
>> + if (host->state != STATE_SENDING_CMD11)
>> + dev_info(host->dev, "Unexpected CMD11 timeout\n");
>
> If Unexpected CMD11 timeout, can it do just" return"?
> Well, I think Unexpected CMD11 timeout is an rare case.
Duh, of course. I'm happy to respin this or I'm happy if you want to
just add a "return;" Please let me know.
-Doug
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