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
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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