From 71ba043e5c5575f3d86536acade70dab6599489b Mon Sep 17 00:00:00 2001
From: Vincent Fazio <vfazio@xes-inc.com>
Date: Mon, 13 Sep 2021 11:22:30 -0500
Subject: [PATCH] arm: rpi: fallback to max clock rate for MMC clock
In rpi-firmware 25e2b597ebfb2495eab4816a276758dcc6ea21f1 and later,
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
U-Boot does not call SET_CLOCK_RATE so bcm2835_get_mmc_clock will
return zero and can cause degraded MMC performance.
Calling SET_CLOCK_RATE fixes the frequency of the clock to a specific
value and disables the firmware's clock scaling so is not an option.
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>
---
arch/arm/mach-bcm283x/include/mach/mbox.h | 2 ++
arch/arm/mach-bcm283x/msg.c | 20 +++++++++++++++++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-bcm283x/include/mach/mbox.h b/arch/arm/mach-bcm283x/include/mach/mbox.h
index 2ae2d3d97c3..7dcac583cc4 100644
--- a/arch/arm/mach-bcm283x/include/mach/mbox.h
+++ b/arch/arm/mach-bcm283x/include/mach/mbox.h
@@ -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
diff --git a/arch/arm/mach-bcm283x/msg.c b/arch/arm/mach-bcm283x/msg.c
index 347aece3cd8..e2badfecb09 100644
--- a/arch/arm/mach-bcm283x/msg.c
+++ b/arch/arm/mach-bcm283x/msg.c
@@ -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 +91,24 @@ 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)