Re: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider

Chris Ball
2010-10-05T02:34:05Z

Hi David,

On Thu, Sep 30, 2010 at 08:03:14PM -0700, Philip Rakity wrote:
> From: Philip Rakity <prakity@marvell.com>
> Date: Thu, 30 Sep 2010 15:34:24 -0700
> Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
>
> The sd 3.0 host spec does not require the clock divider to be a power of 2.
>
> Signed-off-by: Philip Rakity <prakity@marvell.com>
> ---
> drivers/mmc/host/sdhci.c | 8 +++-----
> 1 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 96c7f60..73a94fe 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> goto out;
>
> if (host->version >= SDHCI_SPEC_300) {
> - /* Version 3.00 divisors must be a multiple of 2. */
> if (host->max_clk <= clock)
> div = 1;
> else {
> - for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
> - if ((host->max_clk / div) <= clock)
> - break;
> - }
> + div = host->max_clk/clock;
> + if (host->max_clk % clock)
> + div++;
> }
> } else {
> /* Version 2.00 divisors must be a power of 2. */
> --

Would you mind reviewing this, please? I don't have access to the 3.0
spec.

Thanks very much,

--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child