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arm: rpi: fallback to max clock rate for MMC clock

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In rpi-firmware 25e2b597ebfb2495eab4816a276758dcc6ea21f1,
the GET_CLOCK_RATE mailbox property was changed to return the last
value set by SET_CLOCK_RATE.

https://github.com/raspberrypi/firmware/issues/1619#issuecomment-917025502

Due to this change in firmware behavior, bcm2835_get_mmc_clock now
returns a clock rate of zero since we do not issue SET_CLOCK_RATE.
This results in degraded MMC performance.

SET_CLOCK_RATE fixes the clock to a specific value and disables scaling
so is not an ideal solution.

Instead, fallback to GET_MAX_CLOCK_RATE in bcm2835_get_mmc_clock if
GET_CLOCK_RATE returns zero.

Signed-off-by: Vincent Fazio <vfazio@xes-inc.com>
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
This commit is contained in:
Vincent Fazio 2021-09-14 13:19:18 -05:00 • committed by Peter Robinson
parent 0e8c94054f
commit 0a36afa823
2 changed files with 20 additions and 1 deletions
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2
arch/arm/mach-bcm283x/include/mach/mbox.h
View file

@ -224,6 +224,8 @@ struct bcm2835_mbox_tag_set_power_state {
};
#define BCM2835_MBOX_TAG_GET_CLOCK_RATE 0x00030002
#define BCM2835_MBOX_TAG_GET_MAX_CLOCK_RATE 0x00030004
#define BCM2835_MBOX_TAG_GET_MIN_CLOCK_RATE 0x00030007
#define BCM2835_MBOX_CLOCK_ID_EMMC 1
#define BCM2835_MBOX_CLOCK_ID_UART 2

19
arch/arm/mach-bcm283x/msg.c
View file

@ -75,6 +75,7 @@ int bcm2835_get_mmc_clock(u32 clock_id)
{
ALLOC_CACHE_ALIGN_BUFFER(struct msg_get_clock_rate, msg_clk, 1);
int ret;
u32 clock_rate = 0;
ret = bcm2835_power_on_module(BCM2835_MBOX_POWER_DEVID_SDHCI);
if (ret)
@ -90,7 +91,23 @@ int bcm2835_get_mmc_clock(u32 clock_id)
return -EIO;
}
return msg_clk->get_clock_rate.body.resp.rate_hz;
clock_rate = msg_clk->get_clock_rate.body.resp.rate_hz;
if (clock_rate == 0) {
BCM2835_MBOX_INIT_HDR(msg_clk);
BCM2835_MBOX_INIT_TAG(&msg_clk->get_clock_rate, GET_MAX_CLOCK_RATE);
msg_clk->get_clock_rate.body.req.clock_id = clock_id;
ret = bcm2835_mbox_call_prop(BCM2835_MBOX_PROP_CHAN, &msg_clk->hdr);
if (ret) {
printf("bcm2835: Could not query max eMMC clock rate\n");
return -EIO;
}
clock_rate = msg_clk->get_clock_rate.body.resp.rate_hz;
}
return clock_rate;
}
int bcm2835_get_video_size(int *widthp, int *heightp)