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Commit 19d614a4 authored by Michał Mirosław's avatar Michał Mirosław Committed by Chris Ball
Browse files

mmc: cb710: partially demystify clock selection 



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

Signed-off-by: default avatarMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent 703aae3d

drivers/mmc/host/cb710-mmc.c

+12 −7
Original line number Diff line number Diff line
@@ -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),