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

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>

diff --git a/arch/arm/mach-bcm283x/include/mach/mbox.h b/arch/arm/mach-bcm283x/include/mach/mbox.h
index 2ae2d3d..7dcac58 100644 (file)
--- 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 fe243e2..68b2773 100644 (file)
--- 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 +91,23 @@ 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)