From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaehoon Chung Subject: Re: [PATCH v6 2/3] mmc: dw_mmc: Honor requests to set the clock to 0 (turn off clock) Date: Fri, 23 Aug 2013 22:21:53 +0900 Message-ID: <521761F1.60203@samsung.com> References: <1377188348-3418-1-git-send-email-dianders@chromium.org> <1377188348-3418-3-git-send-email-dianders@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mailout1.samsung.com ([203.254.224.24]:47940 "EHLO mailout1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754588Ab3HWNVq (ORCPT ); Fri, 23 Aug 2013 09:21:46 -0400 In-reply-to: <1377188348-3418-3-git-send-email-dianders@chromium.org> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Doug Anderson Cc: Chris Ball , Seungwon Jeon , James Hogan , Grant Grundler , Alim Akhtar , Abhilash Kesavan , Tomasz Figa , Olof Johansson , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org Hi Doug, If the clock-gating is enabled, then maybe it's continuously printed the kernel message for Bus_speed. Best Regards, Jaehoon Chung On 08/23/2013 01:19 AM, Doug Anderson wrote: > Previously the dw_mmc driver would ignore any requests to disable the > card's clock. This doesn't seem like a good thing in general, but had > one extra bad side effect in the following situtation: > * mmc core would set clk to 400kHz at boot time while initting > * mmc core would set clk to 0 since no card, but it would be ignored. > * suspend to ram and resume; clocks in the dw_mmc IP block are now 0 > but dw_mmc thinks that they're 400kHz (it ignored the set to 0). > * insert card > * mmc core would set clk to 400kHz which would be considered a no-op. > > Note that if there is no card in the slot and we do a suspend/resume > cycle, we _do_ still end up with differences in a dw_mmc register > dump, but the differences are clock related and we've got the clock > disabled both before and after, so this should be OK. > > Signed-off-by: Doug Anderson > --- > Changes in v6: > - Replaces previous pathes that ensured saving/restoring clocks. > > drivers/mmc/host/dw_mmc.c | 21 +++++++++++---------- > 1 file changed, 11 insertions(+), 10 deletions(-) > > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c > index ee5f167..f6c7545 100644 > --- a/drivers/mmc/host/dw_mmc.c > +++ b/drivers/mmc/host/dw_mmc.c > @@ -635,7 +635,11 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit) > u32 div; > u32 clk_en_a; > > - if (slot->clock != host->current_speed || force_clkinit) { > + if (slot->clock == 0) { > + mci_writel(host, CLKENA, 0); > + mci_send_cmd(slot, > + SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0); > + } else if (slot->clock != host->current_speed || force_clkinit) { > div = host->bus_hz / slot->clock; > if (host->bus_hz % slot->clock && host->bus_hz > slot->clock) > /* > @@ -675,9 +679,8 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit) > /* inform CIU */ > mci_send_cmd(slot, > SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0); > - > - host->current_speed = slot->clock; > } > + host->current_speed = slot->clock; > > /* Set the current slot bus width */ > mci_writel(host, CTYPE, (slot->ctype << slot->id)); > @@ -807,13 +810,11 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) > > mci_writel(slot->host, UHS_REG, regs); > > - if (ios->clock) { > - /* > - * Use mirror of ios->clock to prevent race with mmc > - * core ios update when finding the minimum. > - */ > - slot->clock = ios->clock; > - } > + /* > + * Use mirror of ios->clock to prevent race with mmc > + * core ios update when finding the minimum. > + */ > + slot->clock = ios->clock; > > if (drv_data && drv_data->set_ios) > drv_data->set_ios(slot->host, ios); >