platform/x86/amd/pmc: Detect when STB is not available

Loading the amd_pmc module as:

    amd_pmc enable_stb=1

...can result in the following messages in the kernel ring buffer:

    amd_pmc AMDI0009:00: SMU cmd failed. err: 0xff
    ioremap on RAM at 0x0000000000000000 - 0x0000000000ffffff
    WARNING: CPU: 10 PID: 2151 at arch/x86/mm/ioremap.c:217 __ioremap_caller+0x2cd/0x340

Further debugging reveals that this occurs when the requests for
S2D_PHYS_ADDR_LOW and S2D_PHYS_ADDR_HIGH return a value of 0,
indicating that the STB is inaccessible. To prevent the ioremap
warning and provide clarity to the user, handle the invalid address
and display an error message.

Link: https://lore.kernel.org/platform-driver-x86/[email protected]
Fixes: 3d7d407 ("platform/x86: amd-pmc: Add support for AMD Spill to DRAM STB feature")
Acked-by: Shyam Sundar S K <[email protected]>
Signed-off-by: Corey Hickey <[email protected]>
Reviewed-by: Ilpo Järvinen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Hans de Goede <[email protected]>
Signed-off-by: Hans de Goede <[email protected]>

Author: bugfood

drivers/platform/x86/amd/pmc/pmc.c

@@ -998,6 +998,11 @@ static int amd_pmc_s2d_init(struct amd_pmc_dev *dev)
 	amd_pmc_send_cmd(dev, S2D_PHYS_ADDR_LOW, &phys_addr_low, dev->s2d_msg_id, true);
 	amd_pmc_send_cmd(dev, S2D_PHYS_ADDR_HIGH, &phys_addr_hi, dev->s2d_msg_id, true);
 
+	if (!phys_addr_hi && !phys_addr_low) {
+		dev_err(dev->dev, "STB is not enabled on the system; disable enable_stb or contact system vendor\n");
+		return -EINVAL;
+	}
+
 	stb_phys_addr = ((u64)phys_addr_hi << 32 | phys_addr_low);
 
 	/* Clear msg_port for other SMU operation */