On Tue, Sep 28, 2010 at 12:05 AM, Philip Rakity <prakity@xxxxxxxxxxx> wrote:
>
> The code snippet
>> + for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
>> if ((host->max_clk / div) <= clock)
>> break;
>
> is not correct. In sdio 3.0 the value is not a power of 2 for the divider but the value to be divided down-- all the bits count
That's the reason using div += 2 instead of div *= 2
> 2) 10-bit Divided Clock
> Host Controller Version 3.00 supports this mandatory mode instead of the
> 8-bit Divided Clock Mode. The length of the divider is extended to 10 bits and all
> divider values shall be supported.
> 3FFh 1/2046 Divided Clock
>
> Philip
>
> Hi Zhangfei,
>
> On Sat, Sep 25, 2010 at 12:23:33AM -0400, zhangfei gao wrote:
>> From: Zhangfei Gao <zhangfei.gao@xxxxxxxxxxx>
>> Date: Mon, 20 Sep 2010 15:15:18 -0400
>> Subject: [PATCH] sdhci: correct f_min in sd 3.0
>>
>> Signed-off-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxxx>
>> ---
>> drivers/mmc/host/sdhci.c | 8 +++++---
>> drivers/mmc/host/sdhci.h | 3 +++
>> 2 files changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 5928b0a..829e78a 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -1007,14 +1007,14 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>> if (host->max_clk <= clock)
>> div = 1;
>> else {
>> - for (div = 2; div < 2046; div += 2) {
>> + for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
>> if ((host->max_clk / div) <= clock)
>> break;
>> }
>> }
>> } else {
>> /* Version 2.00 divisors must be a power of 2. */
>> - for (div = 1; div < 256; div *= 2) {
>> + for (div = 1; div < SDHCI_MAX_DIV_SPEC_200; div *= 2) {
>> if ((host->max_clk / div) <= clock)
>> break;
>> }
>> @@ -1836,8 +1836,10 @@ int sdhci_add_host(struct sdhci_host *host)
>> mmc->ops = &sdhci_ops;
>> if (host->ops->get_min_clock)
>> mmc->f_min = host->ops->get_min_clock(host);
>> + else if (host->version >= SDHCI_SPEC_300)
>> + mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
>> else
>> - mmc->f_min = host->max_clk / 256;
>> + mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;
>> mmc->f_max = host->max_clk;
>> mmc->caps |= MMC_CAP_SDIO_IRQ;
>>
>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>> index ae28a31..d35fb3d 100644
>> --- a/drivers/mmc/host/sdhci.h
>> +++ b/drivers/mmc/host/sdhci.h
>> @@ -185,6 +185,9 @@
>> #define SDHCI_SPEC_200 1
>> #define SDHCI_SPEC_300 2
>>
>> +#define SDHCI_MAX_DIV_SPEC_200 256
>> +#define SDHCI_MAX_DIV_SPEC_300 2046
>> +
>> struct sdhci_ops;
>>
>> struct sdhci_host {
>
> Thanks very much, I've applied this to mmc-next now.
>
> - Chris.
> --
> Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/>
> One Laptop Per Child
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