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authorDouglas Anderson <dianders@chromium.org>2017-04-11 15:55:43 -0700
committerUlf Hansson <ulf.hansson@linaro.org>2017-04-18 20:59:33 +0200
commita6db2c86033bc41329770e90c20d4f1fec3824e4 (patch)
parent5ef1ecf060f28ecef313b5723f1fd39bf5a35f56 (diff)
mmc: dw_mmc: Don't allow Runtime PM for SDIO cards
According to the SDIO standard interrupts are normally signalled in a very complicated way. They require the card clock to be running and require the controller to be paying close attention to the signals coming from the card. This simply can't happen with the clock stopped or with the controller in a low power mode. To that end, we'll disable runtime_pm when we detect that an SDIO card was inserted. This is much like with what we do with the special "SDMMC_CLKEN_LOW_PWR" bit that dw_mmc supports. NOTE: we specifically do this Runtime PM disabling at card init time rather than in the enable_sdio_irq() callback. This is _different_ than how SDHCI does it. Why do we do it differently? - Unlike SDHCI, dw_mmc uses the standard sdio_irq code in Linux (AKA dw_mmc doesn't set MMC_CAP2_SDIO_IRQ_NOTHREAD). - Because we use the standard sdio_irq code: - We see a constant stream of enable_sdio_irq(0) and enable_sdio_irq(1) calls. This is because the standard code disables interrupts while processing and re-enables them after. - While interrupts are disabled, there's technically a period where we could get runtime disabled while processing interrupts. - If we are runtime disabled while processing interrupts, we'll reset the controller at resume time (see dw_mci_runtime_resume), which seems like a terrible idea because we could possibly have another interrupt pending. To fix the above isues we'd want to put something in the standard sdio_irq code that makes sure to call pm_runtime get/put when interrupts are being actively being processed. That's possible to do, but it seems like a more complicated mechanism when we really just want the runtime pm disabled always for SDIO cards given that all the other bits needed to get Runtime PM vs. SDIO just aren't there. NOTE: at some point in time someone might come up with a fancy way to do SDIO interrupts and still allow (some) amount of runtime PM. Technically we could turn off the card clock if we used an alternate way of signaling SDIO interrupts (and out of band interrupt is one way to do this). We probably wouldn't actually want to fully runtime suspend in this case though--at least not with the current dw_mci_runtime_resume() which basically fully resets the controller at resume time. Fixes: e9ed8835e990 ("mmc: dw_mmc: add runtime PM callback") Cc: <stable@vger.kernel.org> Reported-by: Brian Norris <briannorris@chromium.org> Signed-off-by: Douglas Anderson <dianders@chromium.org> Acked-by: Jaehoon Chung <jh80.chung@samsung.com> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index a9ac0b457313..8718432751c5 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -22,6 +22,7 @@
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/stat.h>
@@ -1621,10 +1622,16 @@ static void dw_mci_init_card(struct mmc_host *mmc, struct mmc_card *card)
if (card->type == MMC_TYPE_SDIO ||
card->type == MMC_TYPE_SD_COMBO) {
- set_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
+ if (!test_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags)) {
+ pm_runtime_get_noresume(mmc->parent);
+ set_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
+ }
clk_en_a = clk_en_a_old & ~clken_low_pwr;
} else {
- clear_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
+ if (test_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags)) {
+ pm_runtime_put_noidle(mmc->parent);
+ clear_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
+ }
clk_en_a = clk_en_a_old | clken_low_pwr;