Re: [PATCH 2/2] firmware: socfpga: set APPLYCFG after loading bitstream

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 18.06.21 10:09, Steffen Trumtrar wrote:
> To make changes to the SDRAM controller effective, the APPLYCFG bit must
> be set after programming the bitstream to the FPGA. This has to be done
> without any SDRAM usage. Therefore copy the function to execute to the
> OCRAM and execute it from there.
> 
> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> ---

> +extern void socfpga_sdram_apply_static_cfg(void __iomem *sdrctrlgrp);
> +extern void socfpga_sdram_apply_static_cfg_end(void *);
> +
>  struct fpgamgr {
>  	struct firmware_handler fh;
>  	struct device_d dev;
> @@ -353,6 +359,9 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  {
>  	struct fpgamgr *mgr = container_of(fh, struct fpgamgr, fh);
>  	int status;
> +	unsigned int func_size = &socfpga_sdram_apply_static_cfg_end -
> +				 &socfpga_sdram_apply_static_cfg;

This is wildly undefined. Kernel users of fncpy I looked at as well as the fncpy
documentation itself suggest doing the arithmetic in assembly instead. See below.

> +	void (*ocram_func)(void __iomem *ocram_base);
>  
>  	/* Ensure the FPGA entering config done */
>  	status = fpgamgr_program_poll_cd(mgr);
> @@ -382,6 +391,18 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  		return status;
>  	}
>  
> +	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_CACHED);
> +
> +	dev_dbg(&mgr->dev, "Setting APPLYCFG bit...\n");
> +
> +	ocram_func = fncpy((void __iomem *)CYCLONE5_OCRAM_ADDRESS,
> +			   &socfpga_sdram_apply_static_cfg, func_size);
> +
> +	sync_caches_for_execution();
> +
> +	ocram_func((void __iomem *) (CYCLONE5_SDR_ADDRESS +
> +				     SDR_CTRLGRP_STATICCFG_ADDRESS));
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/firmware/socfpga_sdr.S b/drivers/firmware/socfpga_sdr.S
> new file mode 100644
> index 000000000000..d634d6362722
> --- /dev/null
> +++ b/drivers/firmware/socfpga_sdr.S
> @@ -0,0 +1,17 @@
> +#include <linux/linkage.h>
> +
> +	.arch	armv7-a
> +	.arm
> +
> +/*
> + * r0 : sdram controller staticcfg
> + */
> +
> +ENTRY(socfpga_sdram_apply_static_cfg)
> +	push {ip,lr}
> +	ldr r1, [r0]
> +	orr r1, r1, #8
> +	str r1, [r0]
> +	pop {ip,pc}
> +	.align
> +ENTRY(socfpga_sdram_apply_static_cfg_end)

Alternative:

ENDPROC(socfpga_sdram_apply_static_cfg)

ENTRY(socfpga_sdram_apply_static_sz)      
	.word . - socfpga_sdram_apply_static_cfg

And then size is accessible from C with
extern const u32 socfpga_sdram_apply_static_cfg_sz;

This makes for a clean disassembly and avoids the undefined
behavior above.

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
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