On Tue, Jan 05, 2010 at 05:07:21AM +0800, Hein_Tibosch wrote: > On 3-1-2010 07:38, Pierre Ossman wrote: >> >> <cut> >> We all use the same pool of cards so we >> should all be using the same init sequence. If there isn't a single >> frequency where all cards will work, then we'll have to make something >> more advanced where the kernel will try the init several times with >> different clocking. > > On 4-1-2010 20:15, Sascha Hauer wrote: >> The problem was that in some setups the mxcmmc driver allows frequencies >> as low as a few Hz and the card initialization took ages. Increasing the >> frequency to 400kHz seemed sensible since it's the value the spec >> describes. 50kHz should be fine as well. >> > > I tried out several main-stream sd-cards and with the Atmel (AP7) controller > they all initialize with F between 138 (=f_min) and 280 Khz. > > Below a patch which tries mmc-initialization using several frequencies > from an array 400, 300, 200 and 100. When it comes to 200 Khz, it works. > The two failed attempts lasted about 10 ms together. > > It looks like a hell-of-a-patch but that's because the indentation changes. > > Note that the new mmc_host member f_init will be used later in power_restore > and resume. As power_up always comes first, it should have a descend value > by then. > > But I still wonder, why not just keep using Sascha's patch, changing 400000 > to 50000? Has anyone ever had problems with mmc-init on 50 Khz? I already wrote it to Hein in private, once again for the rest: The original reason to increase the minimum frequency was that the Freescale i.MX MMC core allows minimum frequencies of just a few Hz. With this the card initialisation took ages, so we increased the minimum frequency. 400kHz seemed like a good value since all cards should support this, but I'm also fine with any other value between 50kHz and 400kHz. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
