[PATCH v7 2/3] mmc: dw_mmc: Honor requests to set the clock to 0 (turn off clock)

From: Doug Anderson
Date: Thu Aug 29 2013 - 12:39:38 EST


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 <dianders@xxxxxxxxxxxx>
---
Changes in v7:
- Avoid printing the same clock over and over again w/ MMC_CLKGATE.

Changes in v6:
- Replaces previous pathes that ensured saving/restoring clocks.

drivers/mmc/host/dw_mmc.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index ee5f167..1584705 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -88,6 +88,8 @@ struct idmac_desc {
* @queue_node: List node for placing this node in the @queue list of
* &struct dw_mci.
* @clock: Clock rate configured by set_ios(). Protected by host->lock.
+ * @last_printed_clock: The last clock we printed. Keeping track of this helps
+ * us to avoid spamming the console with CONFIG_MMC_CLKGATE.
* @flags: Random state bits associated with the slot.
* @id: Number of this slot.
* @last_detect_state: Most recently observed card detect state.
@@ -105,6 +107,7 @@ struct dw_mci_slot {
struct list_head queue_node;

unsigned int clock;
+ unsigned int last_printed_clock;
unsigned long flags;
#define DW_MMC_CARD_PRESENT 0
#define DW_MMC_CARD_NEED_INIT 1
@@ -635,7 +638,11 @@ 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)
/*
@@ -646,10 +653,14 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)

div = (host->bus_hz != slot->clock) ? DIV_ROUND_UP(div, 2) : 0;

- dev_info(&slot->mmc->class_dev,
- "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ"
- " div = %d)\n", slot->id, host->bus_hz, slot->clock,
- div ? ((host->bus_hz / div) >> 1) : host->bus_hz, div);
+ if (slot->clock != slot->last_printed_clock || force_clkinit) {
+ dev_info(&slot->mmc->class_dev,
+ "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n",
+ slot->id, host->bus_hz, slot->clock,
+ div ? ((host->bus_hz / div) >> 1) :
+ host->bus_hz, div);
+ slot->last_printed_clock = slot->clock;
+ }

/* disable clock */
mci_writel(host, CLKENA, 0);
@@ -675,9 +686,8 @@ 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 +817,11 @@ 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);
--
1.8.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/