[PATCH] usb: xhci: Use only 32-bit accesses in nvme_writeq/nvme_readq

[Stefan Roese]

Hi Stefan,

On 29.12.20 20:37, Stefan Agner wrote:
> There might be hardware configurations where 64-bit data accesses
> to NVMe registers are not supported properly.  This patch removes
> the readq/writeq so always two 32-bit accesses are used to read/write
> 64-bit NVMe registers, similarly as it is done in Linux kernel.
> 
> This patch fixes operation of NVMe devices on RPi4 Broadcom
> BCM2711 SoC based board, where the VL805 USB XHCI controller is
> connected to the PCIe Root Complex, which is attached to the system
> through the SCB bridge.
> 
> Even though the architecture is 64-bit the PCIe BAR is 32-bit and likely
> the 64-bit wide register accesses initiated by the CPU are not properly
> translated to a sequence of 32-bit PCIe accesses.
> nvme_readq(), for example, always returns same value in upper and lower
> 32-bits, e.g. 0x3c033fff3c033fff which lead to NVMe devices to fail
> probing.
> 
> This fix is analogous to commit 8e2ab05000ab ("usb: xhci: Use only
> 32-bit accesses in xhci_writeq/xhci_readq").

I see. This is where you cloned the patch subject line from then. ;)

Please change the subject line and add my:

Reviewed-by: Stefan Roese <sr at denx.de>

Thanks,
Stefan

> Cc: Sylwester Nawrocki <s.nawrocki at samsung.com>
> Cc: Zhikang Zhang <zhikang.zhang at nxp.com>
> Cc: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>
> Cc: Matthias Brugger <mbrugger at suse.com>
> Signed-off-by: Stefan Agner <stefan at agner.ch>
> ---
> 
>   drivers/nvme/nvme.h | 8 --------
>   1 file changed, 8 deletions(-)
> 
> diff --git a/drivers/nvme/nvme.h b/drivers/nvme/nvme.h
> index 0e8cb221a7..aa4b3bac67 100644
> --- a/drivers/nvme/nvme.h
> +++ b/drivers/nvme/nvme.h
> @@ -535,28 +535,20 @@ struct nvme_completion {
>    */
>   static inline u64 nvme_readq(__le64 volatile *regs)
>   {
> -#if BITS_PER_LONG == 64
> -	return readq(regs);
> -#else
>   	__u32 *ptr = (__u32 *)regs;
>   	u64 val_lo = readl(ptr);
>   	u64 val_hi = readl(ptr + 1);
>   
>   	return val_lo + (val_hi << 32);
> -#endif
>   }
>   
>   static inline void nvme_writeq(const u64 val, __le64 volatile *regs)
>   {
> -#if BITS_PER_LONG == 64
> -	writeq(val, regs);
> -#else
>   	__u32 *ptr = (__u32 *)regs;
>   	u32 val_lo = lower_32_bits(val);
>   	u32 val_hi = upper_32_bits(val);
>   	writel(val_lo, ptr);
>   	writel(val_hi, ptr + 1);
> -#endif
>   }
>   
>   struct nvme_bar {
> 


Viele Grüße,
Stefan

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