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

From: laurentiu . tudor
Date: Fri May 10 2019 - 10:58:27 EST


From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>

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@xxxxxxx>
---
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