linux-kernel - Re: [PATCH 2/4] edac: mpc85xx add mpc83xx support

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Date:	Wed, 15 Jul 2009 12:52:49 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	dougthompson@...ssion.com
Cc:	bluesmoke-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] edac: mpc85xx add mpc83xx support

On Wed, 15 Jul 2009 11:38:49 -0600
dougthompson@...ssion.com wrote:

> 
> Add support for the Freescale MPC83xx memory controller to the existing
> driver for the Freescale MPC85xx memory controller. The only difference
> between the two processors are in the CS_BNDS register parsing code, which
> has been changed so it will work on both processors.
> 
> The L2 cache controller does not exist on the MPC83xx, but the OF subsystem
> will not use the driver if the device is not present in the OF device tree.
> 
> 
> Kumar, I had to change the nr_pages calculation to make the math work
> out. I checked it on my board and did the math by hand for a 64GB 85xx
> using 64K pages. In both cases, nr_pages * PAGE_SIZE comes out to the
> correct value. Thanks for the help.
> 
> v1 -> v2:
>   * Use PAGE_SHIFT to parse cs_bnds regardless of board type
>   * Remove special-casing for the 83xx processor
> 
> ...
>
> @@ -789,19 +791,20 @@ static void __devinit mpc85xx_init_csrow
>  		csrow = &mci->csrows[index];
>  		cs_bnds = in_be32(pdata->mc_vbase + MPC85XX_MC_CS_BNDS_0 +
>  				  (index * MPC85XX_MC_CS_BNDS_OFS));
> -		start = (cs_bnds & 0xfff0000) << 4;
> -		end = ((cs_bnds & 0xfff) << 20);
> -		if (start)
> -			start |= 0xfffff;
> -		if (end)
> -			end |= 0xfffff;
> +
> +		start = (cs_bnds & 0xffff0000) >> 16;
> +		end   = (cs_bnds & 0x0000ffff);
>  
>  		if (start == end)
>  			continue;	/* not populated */
>  
> +		start <<= (24 - PAGE_SHIFT);
> +		end   <<= (24 - PAGE_SHIFT);
> +		end    |= (1 << (24 - PAGE_SHIFT)) - 1;

<stares for a while>

That looks like the original code was really really wrong.

The setting of all the lower bits in `end' is funny-looking.  What's
happening here?  Should it be commented?


>  		csrow->first_page = start >> PAGE_SHIFT;
>  		csrow->last_page = end >> PAGE_SHIFT;
> -		csrow->nr_pages = csrow->last_page + 1 - csrow->first_page;
> +		csrow->nr_pages = end + 1 - start;
>  		csrow->grain = 8;
>  		csrow->mtype = mtype;
>  		csrow->dtype = DEV_UNKNOWN;
> @@ -985,6 +988,7 @@ static struct of_device_id mpc85xx_mc_er
>  	{ .compatible = "fsl,mpc8560-memory-controller", },
>  	{ .compatible = "fsl,mpc8568-memory-controller", },
>  	{ .compatible = "fsl,mpc8572-memory-controller", },
> +	{ .compatible = "fsl,mpc8349-memory-controller", },
>  	{ .compatible = "fsl,p2020-memory-controller", },
>  	{},
>  };
> @@ -1001,13 +1005,13 @@ static struct of_platform_driver mpc85xx
>  		   },
>  };
>  
> -
> +#ifdef CONFIG_MPC85xx
>  static void __init mpc85xx_mc_clear_rfxe(void *data)
>  {
>  	orig_hid1[smp_processor_id()] = mfspr(SPRN_HID1);
>  	mtspr(SPRN_HID1, (orig_hid1[smp_processor_id()] & ~0x20000));
>  }
> -
> +#endif
>  
>  static int __init mpc85xx_mc_init(void)
>  {
> @@ -1040,26 +1044,32 @@ static int __init mpc85xx_mc_init(void)
>  		printk(KERN_WARNING EDAC_MOD_STR "PCI fails to register\n");
>  #endif
>  
> +#ifdef CONFIG_MPC85xx
>  	/*
>  	 * need to clear HID1[RFXE] to disable machine check int
>  	 * so we can catch it
>  	 */
>  	if (edac_op_state == EDAC_OPSTATE_INT)
>  		on_each_cpu(mpc85xx_mc_clear_rfxe, NULL, 0);
> +#endif
>  
>  	return 0;
>  }

The patch adds lots of ifdefs :(

>  module_init(mpc85xx_mc_init);
>  
> +#ifdef CONFIG_MPC85xx
>  static void __exit mpc85xx_mc_restore_hid1(void *data)
>  {
>  	mtspr(SPRN_HID1, orig_hid1[smp_processor_id()]);
>  }
> +#endif

afacit this will run smp_processor_id() from within preemptible code,
which is often buggy on preemptible kernels and will cause runtime
warnings on at least some architectures.

>  static void __exit mpc85xx_mc_exit(void)
>  {
> +#ifdef CONFIG_MPC85xx
>  	on_each_cpu(mpc85xx_mc_restore_hid1, NULL, 0);
> +#endif
>  #ifdef CONFIG_PCI
>  	of_unregister_platform_driver(&mpc85xx_pci_err_driver);
>  #endif
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