| Message ID | 20200421165059.19394-7-s.nawrocki@samsung.com |
|---|---|
| State | New |
| Headers | show |
| Series | USB host support for Raspberry Pi 4 board | expand |
Hi Sylwester, On Wed, Apr 22, 2020 at 12:51 AM Sylwester Nawrocki <s.nawrocki at samsung.com> wrote: > > This patch adds a Kconfig option which allows accessing 64-bit xHCI > IO registers only with 2 double word accesses rather than using > a single quad word access. There might be HW configurations where > single quad word access doesn't work, even though the CPU is 64-bit. > That seems to be the case on rpi4 board with Broadcom BCM2711 SoC, > where the VL805 USB xHCI hub is connected to the PCIe controller > behind the SCB bridge. > > Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com> > --- > So far I couldn't come up with anything better to make the xHCI host > controller working on the rpi4 board. For some reason dereferencing > a 64-bit pointer to access 64-bit registers doesn't work there, > might be a limitation of the PCIe bridge behind the SCB. In Linux > always 2 double word accesses are used. If Linux always uses 2 double word accesses, let's simply do the same in U-Boot by removing the readq/writeq. > --- > drivers/usb/host/Kconfig | 7 +++++++ > include/usb/xhci.h | 4 ++-- > 2 files changed, 9 insertions(+), 2 deletions(-) > Regards, Bin
On Tue, 2020-04-21 at 18:50 +0200, Sylwester Nawrocki wrote: > This patch adds a Kconfig option which allows accessing 64-bit xHCI > IO registers only with 2 double word accesses rather than using > a single quad word access. There might be HW configurations where > single quad word access doesn't work, even though the CPU is 64-bit. > That seems to be the case on rpi4 board with Broadcom BCM2711 SoC, > where the VL805 USB xHCI hub is connected to the PCIe controller > behind the SCB bridge. > > Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com> > --- > So far I couldn't come up with anything better to make the xHCI host > controller working on the rpi4 board. For some reason dereferencing > a 64-bit pointer to access 64-bit registers doesn't work there, > might be a limitation of the PCIe bridge behind the SCB. In Linux > always 2 double word accesses are used. Out of curiosity, what are the benefits of using 64bit accesses anyway? I'm under the impression that 64 bit accesses are not used that much in xHCI anyway. We could simply default Linux's behavior and save some maintenance burden. Regards, Nicolas -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 488 bytes Desc: This is a digitally signed message part URL: <https://lists.denx.de/pipermail/u-boot/attachments/20200422/f6d926d7/attachment.sig>
Hi Bin, On 22.04.2020 08:00, Bin Meng wrote: > On Wed, Apr 22, 2020 at 12:51 AM Sylwester Nawrocki > <s.nawrocki at samsung.com> wrote: [...] >> So far I couldn't come up with anything better to make the xHCI host >> controller working on the rpi4 board. For some reason dereferencing >> a 64-bit pointer to access 64-bit registers doesn't work there, >> might be a limitation of the PCIe bridge behind the SCB. In Linux >> always 2 double word accesses are used. > > If Linux always uses 2 double word accesses, let's simply do the same > in U-Boot by removing the readq/writeq. Thanks for your review. That sounds good to me, I will do it that way in next iteration. -- Regards, Sylwester
diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig index 0987ff2..3990b8a 100644 --- a/drivers/usb/host/Kconfig +++ b/drivers/usb/host/Kconfig @@ -15,6 +15,13 @@ config USB_XHCI_HCD if USB_XHCI_HCD +config XHCI_64BIT_DWORD_ACCESS_ONLY + bool "Access xHCI 64-bit registers with double word accesses only" + help + Choose this option if your hardware does not support quad word accesses + for registers with 64-bit address pointers. + If unsure, say Y. + config USB_XHCI_DWC3 bool "DesignWare USB3 DRD Core Support" help diff --git a/include/usb/xhci.h b/include/usb/xhci.h index 6017504..459e76b 100644 --- a/include/usb/xhci.h +++ b/include/usb/xhci.h @@ -1111,7 +1111,7 @@ static inline void xhci_writel(uint32_t volatile *regs, const unsigned int val) */ static inline u64 xhci_readq(__le64 volatile *regs) { -#if BITS_PER_LONG == 64 +#if BITS_PER_LONG == 64 && !defined(CONFIG_XHCI_64BIT_DWORD_ACCESS_ONLY) return readq(regs); #else __u32 *ptr = (__u32 *)regs; @@ -1123,7 +1123,7 @@ static inline u64 xhci_readq(__le64 volatile *regs) static inline void xhci_writeq(__le64 volatile *regs, const u64 val) { -#if BITS_PER_LONG == 64 +#if BITS_PER_LONG == 64 && !defined(CONFIG_XHCI_64BIT_DWORD_ACCESS_ONLY) writeq(val, regs); #else __u32 *ptr = (__u32 *)regs;
This patch adds a Kconfig option which allows accessing 64-bit xHCI IO registers only with 2 double word accesses rather than using a single quad word access. There might be HW configurations where single quad word access doesn't work, even though the CPU is 64-bit. That seems to be the case on rpi4 board with Broadcom BCM2711 SoC, where the VL805 USB xHCI hub is connected to the PCIe controller behind the SCB bridge. Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com> --- So far I couldn't come up with anything better to make the xHCI host controller working on the rpi4 board. For some reason dereferencing a 64-bit pointer to access 64-bit registers doesn't work there, might be a limitation of the PCIe bridge behind the SCB. In Linux always 2 double word accesses are used. --- drivers/usb/host/Kconfig | 7 +++++++ include/usb/xhci.h | 4 ++-- 2 files changed, 9 insertions(+), 2 deletions(-)