Re: [PATCH v4 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

[Ramuthevar, Vadivel MuruganX]

Hi Boris,

On 30/4/2020 9:01 pm, Boris Brezillon wrote:
> On Thu, 30 Apr 2020 14:36:00 +0200
> Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote:
>
> > On Thu, 30 Apr 2020 17:07:03 +0800
> > "Ramuthevar, Vadivel MuruganX"
> > <vadivel.muruganx.ramuthevar@xxxxxxxxxxxxxxx> wrote:
> >
> > > > > > The question is, is it the same value we have in nand_pa or it is
> > > > > > different?
> > > > > >         
> > > > > Different address which is 0xE1400000 NAND_BASE_PHY address.
> > > >
> > > > Then why didn't you tell me they didn't match when I suggested to pass
> > >
> > > sorry, because you keep asking nand_pa after that only I realized that.
> > >    
> > > > nand_pa? So now the question is, what does this address represent?
> > >
> > >                  EBU-MODULE
> > >    _________     _______________________
> > > |         |   |            |NAND CTRL  |
> > > | FPI BUS |==>| CS0(0x174) | 0xE100    ( 0xE14/0xE1C) NAND_PHY_BASE
> > > |_________|   |_CS1(0x17C)_|__________ |
> > >
> > > EBU_CONRTROLLER_BASE : 0xE0F0_0000
> > > HSNAND_BASE: 0xE100_0000
> > > NAND_CS0: 0xE140_0000
> > > NAND_CS1: 0xE1C0_0000
> > >
> > > MEM_REGION_BASE_CS0: 0x17400 (internal to ebu controller )
> > > MEM_REGION_BASE_CS1: 0x17C00
> > >    
> >
> > Hm, I wonder if we shouldn't use a 'ranges' property to describe this
> > address translation. Something like
> >
> > 	ebu@xxx {
> > 		ranges = <0x17400000 0xe1400000 0x1000>,
> > 			 <0x17c00000 0xe1c00000 0x1000>;
> > 		reg = <0x17400000>, <0x17c00000>;
> > 		reg-names = "cs-0", "cs-1";
> > 	}
> >
> > The translated address (0xE1X00000) will be available in res->start,
> > and the non-translated one (0x17X00000) can be retrieved with
> > of_get_address(). All you'd have to do then would be calculate the
> > mask:
> >
> > 	mask = (translated_address & original_address) >> 22;
> > 	num_comp_bits = fls(mask);
> > 	WARN_ON(mask != GENMASK(num_comp_bits - 1, 0));
> >
> > Which allows you to properly set the ADDR_SEL() register without
> > relying on some hardcoded values:
> >
> > 	writel(original_address | EBU_ADDR_SEL_REGEN |
> > 	       EBU_ADDR_COMP_BITS(num_comp_bits),
> > 	       ebu_host->ebu + EBU_ADDR_SEL(csid));
> >
> > That's quite important if we want to merge the xway NAND driver with
> > this one.
>
> Looks like the translation is done at the FPI bus declaration level (see
> [1]). We really need to see the big picture to take a wise decision
> about the bindings. Would you mind pasting your dsti/dts files
> somewhere? It feels like the NAND controller is a sub-part of a more
> generic 'memory' controller, in which case the NAND controller should be
> declared as a child of this generic memory bus (called localbus in [1],
> but maybe EBU is more accurate).
>
> [1]https://github.com/xieyaxiongfly/Atheros_CSI_tool_OpenWRT_src/blob/master/target/linux/lantiq/files-4.14/arch/mips/boot/dts/vr9.dtsi#L162


 ebu_nand: ebu_nand@e0f00000 {
                 compatible = "intel,lgm-ebu-nand";
                 reg = <0xe0f00000 0x100
                 0xe1000000 0x300
                 0xe1400000 0x80000
                 0xe1c00000 0x10000>;
                 reg-names = "ebunand", "hsnand", "nand_cs0", nand_cs1";
                 dmas = <&dma0 8>, <&dma0 9>;
                 dma-names = "ebu_rx", "ebu_tx";
                 clocks =  <&cgu0 LGM_GCLK_EBU>;
         };


	 &ebu_nand {
	         status = "disabled";
	        nand,cs = <1>;
	        nand-ecc-mode = "hw";
	        pinctrl-names = "default";
	        pinctrl-0 = <&ebu_nand_base &ebu_cs1>;
	};

>