MIPS: BCM47XX: Setup struct device for the SoC

commit 321c46b91550adc03054125fa7a1639390608e1a upstream.

So far we never had any device registered for the SoC. This resulted in
some small issues that we kept ignoring like:
1) Not working GPIOLIB_IRQCHIP (gpiochip_irqchip_add_key() failing)
2) Lack of proper tree in the /sys/devices/
3) mips_dma_alloc_coherent() silently handling empty coherent_dma_mask

Kernel 4.19 came with a lot of DMA changes and caused a regression on
bcm47xx. Starting with the commit f8c55dc6e828 ("MIPS: use generic dma
noncoherent ops for simple noncoherent platforms") DMA coherent
allocations just fail. Example:
[    1.114914] bgmac_bcma bcma0:2: Allocation of TX ring 0x200 failed
[    1.121215] bgmac_bcma bcma0:2: Unable to alloc memory for DMA
[    1.127626] bgmac_bcma: probe of bcma0:2 failed with error -12
[    1.133838] bgmac_bcma: Broadcom 47xx GBit MAC driver loaded

The bgmac driver also triggers a WARNING:
[    0.959486] ------------[ cut here ]------------
[    0.964387] WARNING: CPU: 0 PID: 1 at ./include/linux/dma-mapping.h:516 bgmac_enet_probe+0x1b4/0x5c4
[    0.973751] Modules linked in:
[    0.976913] CPU: 0 PID: 1 Comm: swapper Not tainted 4.19.9 #0
[    0.982750] Stack : 804a0000 804597c4 00000000 00000000 80458fd8 8381bc2c 838282d4 80481a47
[    0.991367]         8042e3ec 00000001 804d38f0 00000204 83980000 00000065 8381bbe0 6f55b24f
[    0.999975]         00000000 00000000 80520000 00002018 00000000 00000075 00000007 00000000
[    1.008583]         00000000 80480000 000ee811 00000000 00000000 00000000 80432c00 80248db8
[    1.017196]         00000009 00000204 83980000 803ad7b0 00000000 801feeec 00000000 804d0000
[    1.025804]         ...
[    1.028325] Call Trace:
[    1.030875] [<8000aef8>] show_stack+0x58/0x100
[    1.035513] [<8001f8b4>] __warn+0xe4/0x118
[    1.039708] [<8001f9a4>] warn_slowpath_null+0x48/0x64
[    1.044935] [<80248db8>] bgmac_enet_probe+0x1b4/0x5c4
[    1.050101] [<802498e0>] bgmac_probe+0x558/0x590
[    1.054906] [<80252fd0>] bcma_device_probe+0x38/0x70
[    1.060017] [<8020e1e8>] really_probe+0x170/0x2e8
[    1.064891] [<8020e714>] __driver_attach+0xa4/0xec
[    1.069784] [<8020c1e0>] bus_for_each_dev+0x58/0xb0
[    1.074833] [<8020d590>] bus_add_driver+0xf8/0x218
[    1.079731] [<8020ef24>] driver_register+0xcc/0x11c
[    1.084804] [<804b54cc>] bgmac_init+0x1c/0x44
[    1.089258] [<8000121c>] do_one_initcall+0x7c/0x1a0
[    1.094343] [<804a1d34>] kernel_init_freeable+0x150/0x218
[    1.099886] [<803a082c>] kernel_init+0x10/0x104
[    1.104583] [<80005878>] ret_from_kernel_thread+0x14/0x1c
[    1.110107] ---[ end trace f441c0d873d1fb5b ]---

This patch setups a "struct device" (and passes it to the bcma) which
allows fixing all the mentioned problems. It'll also require a tiny bcma
patch which will follow through the wireless tree & its maintainer.

Fixes: f8c55dc6e828 ("MIPS: use generic dma noncoherent ops for simple noncoherent platforms")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-wireless@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/mips/bcm47xx/setup.c

@@ -173,6 +173,31 @@ void __init plat_mem_setup(void)
 	pm_power_off = bcm47xx_machine_halt;
 }
 
+#ifdef CONFIG_BCM47XX_BCMA
+static struct device * __init bcm47xx_setup_device(void)
+{
+	struct device *dev;
+	int err;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return NULL;
+
+	err = dev_set_name(dev, "bcm47xx_soc");
+	if (err) {
+		pr_err("Failed to set SoC device name: %d\n", err);
+		kfree(dev);
+		return NULL;
+	}
+
+	err = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
+	if (err)
+		pr_err("Failed to set SoC DMA mask: %d\n", err);
+
+	return dev;
+}
+#endif
+
 /*
  * This finishes bus initialization doing things that were not possible without
  * kmalloc. Make sure to call it late enough (after mm_init).
@@ -183,6 +208,10 @@ void __init bcm47xx_bus_setup(void)
 	if (bcm47xx_bus_type == BCM47XX_BUS_TYPE_BCMA) {
 		int err;
 
+		bcm47xx_bus.bcma.dev = bcm47xx_setup_device();
+		if (!bcm47xx_bus.bcma.dev)
+			panic("Failed to setup SoC device\n");
+
 		err = bcma_host_soc_init(&bcm47xx_bus.bcma);
 		if (err)
 			panic("Failed to initialize BCMA bus (err %d)", err);
@@ -235,6 +264,8 @@ static int __init bcm47xx_register_bus_complete(void)
 #endif
 #ifdef CONFIG_BCM47XX_BCMA
 	case BCM47XX_BUS_TYPE_BCMA:
+		if (device_register(bcm47xx_bus.bcma.dev))
+			pr_err("Failed to register SoC device\n");
 		bcma_bus_register(&bcm47xx_bus.bcma.bus);
 		break;
 #endif

include/linux/bcma/bcma_soc.h

@@ -6,6 +6,7 @@
 
 struct bcma_soc {
 	struct bcma_bus bus;
+	struct device *dev;
 };
 
 int __init bcma_host_soc_register(struct bcma_soc *soc);