linux-kernel - Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem rework

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Date:   Wed, 15 May 2019 18:28:58 +0200
From:   Fredrik Noring <noring@...rew.org>
To:     Laurentiu Tudor <laurentiu.tudor@....com>
Cc:     Robin Murphy <robin.murphy@....com>, "hch@....de" <hch@....de>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "marex@...x.de" <marex@...x.de>,
        "JuergenUrban@....de" <JuergenUrban@....de>,
        Leo Li <leoyang.li@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem
 rework

Hi Lauretniu,

> I think that any recent kernel will do, so I'd say your current branch 
> should be fine.

The kernel oopses with "unable to handle kernel paging request at virtual
address 000aba0b" in hcd_alloc_coherent via usb_hcd_map_urb_for_dma. This
relates to patch 2/3 that I didn't quite understand, where

-	retval = dma_declare_coherent_memory(dev, mem->start,
-					 mem->start - mem->parent->start,
-					 resource_size(mem));

becomes

+	retval = gen_pool_add_virt(hcd->localmem_pool,
+				   (unsigned long)mem->start -
+					mem->parent->start,
+				   mem->start, resource_size(mem),

so that arguments two and three switch places. Given

int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
				dma_addr_t device_addr, size_t size);

and

int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys
		 size_t size, int nid)

it seems that the device address (dma_addr_t device_addr) now becomes a
virtual address (unsigned long virt). Is that intended?

My corresponding patch is below for reference. I applied your 1/3 patch
to test it.

Fredrik

diff --git a/drivers/usb/host/ohci-ps2.c b/drivers/usb/host/ohci-ps2.c
--- a/drivers/usb/host/ohci-ps2.c
+++ b/drivers/usb/host/ohci-ps2.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/genalloc.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/usb.h>
@@ -92,12 +93,12 @@ static irqreturn_t ohci_ps2_irq(struct usb_hcd *hcd)
 	return ohci_irq(hcd); /* Call normal IRQ handler. */
 }
 
-static int iopheap_alloc_coherent(struct platform_device *pdev,
-	size_t size, int flags)
+static int iopheap_alloc_coherent(struct platform_device *pdev, size_t size)
 {
 	struct device *dev = &pdev->dev;
 	struct usb_hcd *hcd = platform_get_drvdata(pdev);
 	struct ps2_hcd *ps2priv = hcd_to_priv(hcd);
+	int err;
 
 	if (ps2priv->iop_dma_addr != 0)
 		return 0;
@@ -112,28 +113,37 @@ static int iopheap_alloc_coherent(struct platform_device *pdev,
 		return -ENOMEM;
 	}
 
-	if (dma_declare_coherent_memory(dev,
-			iop_bus_to_phys(ps2priv->iop_dma_addr),
-			ps2priv->iop_dma_addr, size, flags)) {
-		dev_err(dev, "dma_declare_coherent_memory failed\n");
-		iop_free(ps2priv->iop_dma_addr);
-		ps2priv->iop_dma_addr = 0;
-		return -ENOMEM;
+	hcd->localmem_pool = devm_gen_pool_create(dev,
+		PAGE_SHIFT, dev_to_node(dev), DRV_NAME);
+	if (IS_ERR(hcd->localmem_pool)) {
+		err = PTR_ERR(hcd->localmem_pool);
+		goto out_err;
+	}
+
+	err = gen_pool_add_virt(hcd->localmem_pool, ps2priv->iop_dma_addr,
+		iop_bus_to_phys(ps2priv->iop_dma_addr), size, dev_to_node(dev));
+	if (err < 0) {
+		dev_err(dev, "gen_pool_add_virt failed with %d\n", err);
+		goto out_err;
 	}
 
 	return 0;
+
+out_err:
+	iop_free(ps2priv->iop_dma_addr);
+	ps2priv->iop_dma_addr = 0;
+
+	return err;
 }
 
 static void iopheap_free_coherent(struct platform_device *pdev)
 {
-	struct device *dev = &pdev->dev;
 	struct usb_hcd *hcd = platform_get_drvdata(pdev);
 	struct ps2_hcd *ps2priv = hcd_to_priv(hcd);
 
 	if (ps2priv->iop_dma_addr == 0)
 		return;
 
-	dma_release_declared_memory(dev);
 	iop_free(ps2priv->iop_dma_addr);
 	ps2priv->iop_dma_addr = 0;
 }
@@ -177,8 +187,7 @@ static int ohci_hcd_ps2_probe(struct platform_device *pdev)
 		goto err;
 	}
 
-	ret = iopheap_alloc_coherent(pdev,
-		DMA_BUFFER_SIZE, DMA_MEMORY_EXCLUSIVE);
+	ret = iopheap_alloc_coherent(pdev, DMA_BUFFER_SIZE);
 	if (ret != 0)
 		goto err_alloc_coherent;