On Mon, Sep 27, 2010 at 5:33 PM, David Vrabel <david.vrabel@xxxxxxx> wrote:
> zhangfei gao wrote:
>> On Mon, Sep 20, 2010 at 10:34 AM, David Vrabel <david.vrabel@xxxxxxx> wrote:
>>> zhangfei gao wrote:
>>>> index 5db49b1..9114c87 100644
>>>> --- a/drivers/mmc/core/core.c
>>>> +++ b/drivers/mmc/core/core.c
>>>> @@ -910,9 +910,9 @@ static void mmc_power_up(struct mmc_host *host)
>>>> if (host->f_min > 400000) {
>>>> pr_warning("%s: Minimum clock frequency too high for "
>>>> "identification mode\n", mmc_hostname(host));
>>>> - host->ios.clock = host->f_min;
>>>> - } else
>>>> host->ios.clock = 400000;
>>>> + } else
>>>> + host->ios.clock = host->f_min;
>>> NAK.
>>>
>>> The code is already correctly requesting 400 kHz (unless the controller
>>> can't go that slow).
>>
>> Original code
>> if (host->f_min > 400000) {
>> pr_warning("%s: Minimum clock frequency too high for "
>> "identification mode\n", mmc_hostname(host));
>> host->ios.clock = host->f_min;
>> } else
>> host->ios.clock = 400000;
>>
>> With this code, the init clock is would be at lease 400 kHz, and no
>> matter how bigger the host->f_min it is, is this really correct?
>
> It's not clear what you're saying or why you think the original code is
> wrong. Consider a host controller that reports a minimum frequency of 1
> Hz. Obviously we wouldn't want to do the card identification at this
> clock rate, yes?
Thanks for your explanation.
The issue you met is f_min is too slow.
The issue we met is f_min is too high which also cause init fail,
But it is OK, we could prevent in other place, duringinit set
mmc->f_min = host->max_clk/256 in sdc 2.0 and mmc->f_min =
host->max_clk/2046 in sdc 3.0
Just curious how to get 400000, which is slowest speed for
initializaion, is this OK for all card?
>
> David
> --
> David Vrabel, Senior Software Engineer, Drivers
> CSR, Churchill House, Cambridge Business Park, Tel: +44 (0)1223 692562
> Cowley Road, Cambridge, CB4 0WZ http://www.csr.com/
>
>
> Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
>
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