linux-kernel - [RFC PATCH 1/3] ohci-hcd: use genalloc for USB HCs with local memory

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Date:   Fri, 10 May 2019 17:56:44 +0300
From:   laurentiu.tudor@....com
To:     hch@....de, stern@...land.harvard.edu, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, marex@...x.de
Cc:     leoyang.li@....com, linux-kernel@...r.kernel.org,
        robin.murphy@....com, Laurentiu Tudor <laurentiu.tudor@....com>
Subject: [RFC PATCH 1/3] ohci-hcd: use genalloc for USB HCs with local memory

From: Laurentiu Tudor <laurentiu.tudor@....com>

For HCs that have local memory, replace the current DMA API usage
with a genalloc generic allocator to manage the mappings for these
devices.
This is in preparation for dropping the existing "coherent" dma
mem declaration APIs. Current implementation was relying on a short
circuit in the DMA API that in the end, was acting as an allocator
for these type of devices.

For context, see thread here: https://lkml.org/lkml/2019/4/22/357

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
---
 drivers/usb/host/ohci-hcd.c | 23 ++++++++++++++++++-----
 drivers/usb/host/ohci.h     |  3 +++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 210181fd98d2..c739d55901b3 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/drivers/usb/host/ohci-hcd.c
@@ -40,6 +40,7 @@
 #include <linux/dmapool.h>
 #include <linux/workqueue.h>
 #include <linux/debugfs.h>
+#include <linux/genalloc.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -505,8 +506,15 @@ static int ohci_init (struct ohci_hcd *ohci)
 	timer_setup(&ohci->io_watchdog, io_watchdog_func, 0);
 	ohci->prev_frame_no = IO_WATCHDOG_OFF;
 
-	ohci->hcca = dma_alloc_coherent (hcd->self.controller,
-			sizeof(*ohci->hcca), &ohci->hcca_dma, GFP_KERNEL);
+	if (hcd->driver->flags & HCD_LOCAL_MEM)
+		ohci->hcca = gen_pool_dma_alloc(ohci->localmem_pool,
+						sizeof(*ohci->hcca),
+						&ohci->hcca_dma);
+	else
+		ohci->hcca = dma_alloc_coherent(hcd->self.controller,
+						sizeof(*ohci->hcca),
+						&ohci->hcca_dma,
+						GFP_KERNEL);
 	if (!ohci->hcca)
 		return -ENOMEM;
 
@@ -990,9 +998,14 @@ static void ohci_stop (struct usb_hcd *hcd)
 	remove_debug_files (ohci);
 	ohci_mem_cleanup (ohci);
 	if (ohci->hcca) {
-		dma_free_coherent (hcd->self.controller,
-				sizeof *ohci->hcca,
-				ohci->hcca, ohci->hcca_dma);
+		if (hcd->driver->flags & HCD_LOCAL_MEM)
+			gen_pool_free(ohci->localmem_pool,
+				      (unsigned long)ohci->hcca,
+				      sizeof(*ohci->hcca));
+		else
+			dma_free_coherent(hcd->self.controller,
+					  sizeof(*ohci->hcca),
+					  ohci->hcca, ohci->hcca_dma);
 		ohci->hcca = NULL;
 		ohci->hcca_dma = 0;
 	}
diff --git a/drivers/usb/host/ohci.h b/drivers/usb/host/ohci.h
index ef4813bfc5bf..cd196172c6fd 100644
--- a/drivers/usb/host/ohci.h
+++ b/drivers/usb/host/ohci.h
@@ -367,6 +367,9 @@ struct ohci_hcd {
 	 */
 	struct ohci_regs __iomem *regs;
 
+	/* allocator for HCs having local memory */
+	struct gen_pool         *localmem_pool;
+
 	/*
 	 * main memory used to communicate with the HC (dma-consistent).
 	 * hcd adds to schedule for a live hc any time, but removals finish
-- 
2.17.1