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SubjectRe: [PATCH 2/2] usb: host: Fix excessive alignment restriction for local memory allocations
On Tue, Jun 25, 2019 at 05:08:23PM +0200, Fredrik Noring wrote:
> The PAGE_SHIFT alignment restriction to devm_gen_pool_create() quickly
> exhaust local memory because most allocations are much smaller than
> PAGE_SIZE. This causes USB device failures such as
>
> usb 1-2.1: reset full-speed USB device number 4 using sm501-usb
> sd 1:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x03 driverbyte=0x00
> sd 1:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 00 00 08 7c 00 00 f0 00
> print_req_error: I/O error, dev sda, sector 2172 flags 80700
>
> when trying to boot from the SM501 USB controller on SH4 with QEMU.
>
> Align allocations as required but not necessarily much more than that.
> The HCCA, TD and ED structures align with 256, 32 and 16 byte memory
> boundaries, as specified by the Open HCI[1]. The min_alloc_order argument
> to devm_gen_pool_create is now somewhat arbitrarily set to 4 (16 bytes).
> Perhaps it could be somewhat lower for general buffer allocations.
>
> Reference:
>
> [1] "Open Host Controller Interface Specification for USB",
> release 1.0a, Compaq, Microsoft, National Semiconductor, 1999,
> pp. 16, 19, 33.
>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Fredrik Noring <noring@nocrew.org>

Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
> drivers/usb/core/hcd.c | 2 +-
> drivers/usb/host/ohci-hcd.c | 4 ++--
> drivers/usb/host/ohci-mem.c | 6 ++++--
> 3 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index b2362303d32f..48483fa71854 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -3014,7 +3014,7 @@ int usb_hcd_setup_local_mem(struct usb_hcd *hcd, phys_addr_t phys_addr,
> int err;
> void __iomem *local_mem;
>
> - hcd->localmem_pool = devm_gen_pool_create(hcd->self.sysdev, PAGE_SHIFT,
> + hcd->localmem_pool = devm_gen_pool_create(hcd->self.sysdev, 4,
> dev_to_node(hcd->self.sysdev),
> dev_name(hcd->self.sysdev));
> if (IS_ERR(hcd->localmem_pool))
> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
> index 5801858d867e..b457fdaff297 100644
> --- a/drivers/usb/host/ohci-hcd.c
> +++ b/drivers/usb/host/ohci-hcd.c
> @@ -507,9 +507,9 @@ static int ohci_init (struct ohci_hcd *ohci)
> ohci->prev_frame_no = IO_WATCHDOG_OFF;
>
> if (hcd->localmem_pool)
> - ohci->hcca = gen_pool_dma_alloc(hcd->localmem_pool,
> + ohci->hcca = gen_pool_dma_alloc_align(hcd->localmem_pool,
> sizeof(*ohci->hcca),
> - &ohci->hcca_dma);
> + &ohci->hcca_dma, 256);
> else
> ohci->hcca = dma_alloc_coherent(hcd->self.controller,
> sizeof(*ohci->hcca),
> diff --git a/drivers/usb/host/ohci-mem.c b/drivers/usb/host/ohci-mem.c
> index 4afe27cc7e46..1425335c6baf 100644
> --- a/drivers/usb/host/ohci-mem.c
> +++ b/drivers/usb/host/ohci-mem.c
> @@ -94,7 +94,8 @@ td_alloc (struct ohci_hcd *hc, gfp_t mem_flags)
> struct usb_hcd *hcd = ohci_to_hcd(hc);
>
> if (hcd->localmem_pool)
> - td = gen_pool_dma_zalloc(hcd->localmem_pool, sizeof(*td), &dma);
> + td = gen_pool_dma_zalloc_align(hcd->localmem_pool,
> + sizeof(*td), &dma, 32);
> else
> td = dma_pool_zalloc(hc->td_cache, mem_flags, &dma);
> if (td) {
> @@ -137,7 +138,8 @@ ed_alloc (struct ohci_hcd *hc, gfp_t mem_flags)
> struct usb_hcd *hcd = ohci_to_hcd(hc);
>
> if (hcd->localmem_pool)
> - ed = gen_pool_dma_zalloc(hcd->localmem_pool, sizeof(*ed), &dma);
> + ed = gen_pool_dma_zalloc_align(hcd->localmem_pool,
> + sizeof(*ed), &dma, 16);
> else
> ed = dma_pool_zalloc(hc->ed_cache, mem_flags, &dma);
> if (ed) {
> --
> 2.21.0
>

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