Re: [PATCH] OMAP: fix gpmc nand setup when no timings supplied

[Mike Rapoport <mike@compulab.co.il>]

Tony Lindgren wrote:
> * Mike Rapoport <mike@compulab.co.il> [100422 01:41]:
>> Ghorai, Sukumar wrote:
>>
>> CM-T35, for instance can be assembled with different NAND flash
>> chips. Besides, boards that use NAND as primary boot device, we
>> anyway depend on proper GPMC configuration in the bootloader chain.
>> Having ability to define GPMC timings in the kernel and keep the
>> settings made by the bootloader adds flexibility level for board
>> designers.
> 
> Not implementing the retime function for GPMC will cause issues
> with PM as you cannot scale the L3 frequency without breaking
> your GPMC timings.

I agree that without retime function scaling the frequency will break 
the GPMC timings. But my point was that there should be an _option_ to 
keep the timings defined by the bootloader rather than enforce board 
files to specify timings.
Since skipping the retime function will break gpmc timings in PM-enabled 
  kernel, we need to implement this option in smarter way. E.g. 
something like:

diff --git a/arch/arm/mach-omap2/gpmc-nand.c 
b/arch/arm/mach-omap2/gpmc-nand.c
index 64d74f0..65ac0d0 100644
--- a/arch/arm/mach-omap2/gpmc-nand.c
+++ b/arch/arm/mach-omap2/gpmc-nand.c
@@ -34,6 +34,12 @@ static struct platform_device gpmc_nand_device = {
  	.resource	= &gpmc_nand_resource,
  };

+static int gpmc_nand_detect_timings(void)
+{
+	/* FIXME: implement timings detection */
+	return -EINVAL;
+}
+
  static int omap2_nand_gpmc_retime(void)
  {
  	struct gpmc_timings t;
@@ -109,6 +115,14 @@ int __init gpmc_nand_init(struct 
omap_nand_platform_data *_nand_data)
  		return err;
  	}

+	if (gpmc_nand_data->keep_timings) {
+		err = gpmc_nand_detect_timings();
+		if (err < 0) {
+			dev_err(dev, "Cannot detect GPMC timings\n");
+			return err;
+		}
+	}
+
  	err = gpmc_nand_setup();
  	if (err < 0) {
  		dev_err(dev, "NAND platform setup failed: %d\n", err);
diff --git a/arch/arm/plat-omap/include/plat/nand.h 
b/arch/arm/plat-omap/include/plat/nand.h
index 6ba88d2..cf05d2d 100644
--- a/arch/arm/plat-omap/include/plat/nand.h
+++ b/arch/arm/plat-omap/include/plat/nand.h
@@ -24,6 +24,7 @@ struct omap_nand_platform_data {
  	void __iomem		*gpmc_cs_baseaddr;
  	void __iomem		*gpmc_baseaddr;
  	int			devsize;
+	bool			keep_timings;
  };

  /* size (4 KiB) for IO mapping */



> Tony


-- 
Sincerely yours,
Mike.