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mmc: cb710: partially demystify clock selection

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Clock divider selection in partially verified, so document known facts
in code.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Michał Mirosław 2010-03-21 07:33:08 +01:00 committed by Chris Ball
parent 703aae3d09
commit 19d614a45a
1 changed files with 12 additions and 7 deletions
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19
drivers/mmc/host/cb710-mmc.c
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@ -25,7 +25,7 @@ static const u8 cb710_src_freq_mhz[16] = {
50, 55, 60, 65, 70, 75, 80, 85
};
static void cb710_mmc_set_clock(struct mmc_host *mmc, int hz)
static void cb710_mmc_select_clock_divider(struct mmc_host *mmc, int hz)
{
struct cb710_slot *slot = cb710_mmc_to_slot(mmc);
struct pci_dev *pdev = cb710_slot_to_chip(slot)->pdev;
@ -33,8 +33,11 @@ static void cb710_mmc_set_clock(struct mmc_host *mmc, int hz)
u32 divider_idx;
int src_hz;
/* this is magic, unverifiable for me, unless I get
* MMC card with cables connected to bus signals */
/* on CB710 in HP nx9500:
* src_freq_idx == 0
* indexes 1-7 work as written in the table
* indexes 0,8-15 give no clock output
*/
pci_read_config_dword(pdev, 0x48, &src_freq_idx);
src_freq_idx = (src_freq_idx >> 16) & 0xF;
src_hz = cb710_src_freq_mhz[src_freq_idx] * 1000000;
@ -46,13 +49,15 @@ static void cb710_mmc_set_clock(struct mmc_host *mmc, int hz)
if (src_freq_idx)
divider_idx |= 0x8;
else if (divider_idx == 0)
divider_idx = 1;
cb710_pci_update_config_reg(pdev, 0x40, ~0xF0000000, divider_idx << 28);
dev_dbg(cb710_slot_dev(slot),
"clock set to %d Hz, wanted %d Hz; flag = %d\n",
"clock set to %d Hz, wanted %d Hz; src_freq_idx = %d, divider_idx = %d|%d\n",
src_hz >> cb710_clock_divider_log2[divider_idx & 7],
hz, (divider_idx & 8) != 0);
hz, src_freq_idx, divider_idx & 7, divider_idx & 8);
}
static void __cb710_mmc_enable_irq(struct cb710_slot *slot,
@ -512,7 +517,7 @@ static int cb710_mmc_powerup(struct cb710_slot *slot)
#endif
int err;
/* a lot of magic; see comment in cb710_mmc_set_clock() */
/* a lot of magic for now */
dev_dbg(cb710_slot_dev(slot), "bus powerup\n");
cb710_dump_regs(chip, CB710_DUMP_REGS_MMC);
err = cb710_wait_while_busy(slot, CB710_MMC_S2_BUSY_20);
@ -572,7 +577,7 @@ static void cb710_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
struct cb710_mmc_reader *reader = mmc_priv(mmc);
int err;
cb710_mmc_set_clock(mmc, ios->clock);
cb710_mmc_select_clock_divider(mmc, ios->clock);
if (!cb710_mmc_is_card_inserted(slot)) {
dev_dbg(cb710_slot_dev(slot),