[PATCH] ARM: i.MX6: boot: detect USB serial downloader more reliable

[Ahmad Fatoum]

On 11.08.21 19:36, Marco Felsch wrote:
> The problem with the BootROM is that the SCR registers are not set

s/SCR/SRC/ ?

> accordingly in case of a failed primary boot. E.g. if the device is
> configured to boot from an eMMC and the eMMC is empty or image is
> corrupt, the BootROM goes into 'recovery boot mode' (reference manual
> Figure 8-1) and the last possible recovery option is the serial
> downloader. In such case the SRC registers still indicate that the
> device was booted from an eMMC instead of serial-download.
> 
> This commit ports the U-Boot commit [1] with slightly adaptions suggested
> by Ahmad to Barebox. Also we need to reorder the imx6_init() else we
> reset the otg-controller to early.
> 
> [1] https://source.denx.de/u-boot/u-boot/-/commit/e203dcf23e9eabc2e4f3d0b079457cd1516f2081
> 
> Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> ---
>  arch/arm/mach-imx/boot.c  | 27 +++++++++++++++++++++++++++
>  arch/arm/mach-imx/imx6.c  |  4 ++--
>  include/soc/fsl/fsl_udc.h | 11 +++++++++++
>  3 files changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mach-imx/boot.c b/arch/arm/mach-imx/boot.c
> index 2b66bbf71e..fcb3c10064 100644
> --- a/arch/arm/mach-imx/boot.c
> +++ b/arch/arm/mach-imx/boot.c
> @@ -8,6 +8,7 @@
>  #include <magicvar.h>
>  
>  #include <io.h>
> +#include <mach/clock-imx6.h>
>  #include <mach/generic.h>
>  #include <mach/imx25-regs.h>
>  #include <mach/imx27-regs.h>
> @@ -23,6 +24,7 @@
>  #include <mach/imx8mq.h>
>  #include <mach/imx6.h>
>  
> +#include <soc/fsl/fsl_udc.h>
>  
>  static void
>  imx_boot_save_loc(void (*get_boot_source)(enum bootsource *, int *))
> @@ -397,6 +399,11 @@ static u32 imx6_get_src_boot_mode(void __iomem *src_base)
>  	return readl(src_base + IMX6_SRC_SBMR1);
>  }
>  
> +static inline bool imx6_usboh3_clk_active(void)
> +{
> +	return (readl(MXC_CCM_CCGR6) & 0x3) == 0x3;
> +}
> +
>  void imx6_get_boot_source(enum bootsource *src, int *instance)
>  {
>  	void __iomem *src_base = IOMEM(MX6_SRC_BASE_ADDR);
> @@ -410,6 +417,26 @@ void imx6_get_boot_source(enum bootsource *src, int *instance)
>  
>  	bootsrc = imx53_bootsource_internal(bootmode);
>  
> +	/*
> +	 * imx6_bootsource_serial() can't detect cases where the boot ROM
> +	 * decided to use the serial downloader as a fall back (primary
> +	 * boot source failed).
> +	 *
> +	 * Infer that the boot ROM used the USB serial downloader by
> +	 * checking whether both the UDC and the clock enabling access
> +	 * to its MMIO region are currently active...
> +	 * This assumes:
> +	 * - On fresh boots, PBL doesn't itself start a stopped UDC
> +	 * - In barebox proper, boot source is saved before the UDC driver
> +	 *   may enable the UDC
> +	 */
> +
> +	if (imx6_usboh3_clk_active() &&
> +	    is_chipidea_udc_running(IOMEM(MX6_OTG_BASE_ADDR))) {
> +		*src = BOOTSOURCE_SERIAL;
> +		return;
> +	}
> +
>  	if (imx6_bootsource_serial(sbmr2) ||
>  	    imx6_bootsource_serial_forced(bootsrc)) {
>  		*src = BOOTSOURCE_SERIAL;
> diff --git a/arch/arm/mach-imx/imx6.c b/arch/arm/mach-imx/imx6.c
> index 9ccb391384..fa4cb093c3 100644
> --- a/arch/arm/mach-imx/imx6.c
> +++ b/arch/arm/mach-imx/imx6.c
> @@ -205,10 +205,10 @@ int imx6_init(void)
>  	void __iomem *src = IOMEM(MX6_SRC_BASE_ADDR);
>  	u64 mx6_uid;
>  
> -	imx6_init_lowlevel();
> -
>  	imx6_boot_save_loc();
>  
> +	imx6_init_lowlevel();

A comment inside imx6_init_lowlevel hinting at the dependency w.r.t 
imx6_boot_save_loc would be nice.

Apart from these nitpicks:

Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>

> +
>  	mx6_silicon_revision = imx6_cpu_revision();
>  	mx6_uid = imx6_uid();
>  
> diff --git a/include/soc/fsl/fsl_udc.h b/include/soc/fsl/fsl_udc.h
> index b983f714c5..0b409a9f6b 100644
> --- a/include/soc/fsl/fsl_udc.h
> +++ b/include/soc/fsl/fsl_udc.h
> @@ -1,6 +1,9 @@
>  #ifndef __FSL_UDC_H
>  #define __FSL_UDC_H
>  
> +#include <linux/types.h>
> +#include <io.h>
> +
>  /* USB DR device mode registers (Little Endian) */
>  struct usb_dr_device {
>  	/* Capability register */
> @@ -380,4 +383,12 @@ int imx_barebox_start_usb(void __iomem *dr, void *dest);
>  int imx8mm_barebox_load_usb(void *dest);
>  int imx8mm_barebox_start_usb(void *dest);
>  
> +static inline bool is_chipidea_udc_running(void __iomem *dr)
> +{
> +	struct usb_dr_device __iomem *dr_regs = dr;
> +
> +	return (readl(&dr_regs->usbmode) & USB_MODE_CTRL_MODE_DEVICE)
> +		&& (readl(&dr_regs->usbcmd) & USB_CMD_RUN_STOP);
> +}
> +
>  #endif /* __FSL_UDC_H */
> 


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