Issues with SPI NOR flash

[Andrew Jeffery]

Hi Aaron,

On Tue, 8 Jan 2019, at 21:52, Aaron Williams wrote:
> Hi all,
> 
> I'm running into a problem with the SPI NOR connected to our host processor. 
> We're using a Macronix MX25L25645GMI-08G connected to the spi1 device on an 
> AST2500. This device is muxed between our host processor and the BMC. When our 
> host processor is powered off, the BMC has exclusive access to it.
> 
> Anyway, the behavior is that I can read the SPI NOR without any difficulty, 
> however, when I write to it the SPI nor appears to be filled with garbage. If 
> I had to guess, I'd guess that the SPI driver is not waiting for the SPI NOR 
> to complete the write operation before moving to the next block.
> 
> Here is the relevant section from our device tree:
> 
> &spi1 {
> 	status = "okay";
> 	flash at 0 {
> 		status = "okay";
> 		compatible = "jedec,spi-nor", "spi-nor";
> 		label = "host";
> 		m25p,fast-read;
> 		spi-tx-bus-width = <1>;
> 		spi-rx-bus-width = <1>;
> 		spi-max-frequency = <50000000>;
> 		partitions {
> 			compatible = "fixed-partitions";
> 			#address-cells = <1>;
> 			#size-cells = <1>;
> 
> 			bootloader at 0 {
> 				reg = <0x0 0x1000000>;
> 				label = "host-
> bootloader";
> 			};
> 			kernel at 1000000 {
> 				reg = <0x1000000 
> 0x1000000>;
> 				label = "host-kernel";
> 			};
> 		};
> 	};
> };
> 
> Note that our host is also running 4.19 and has no trouble writing to the SPI 
> NOR. The corruption seems worse when flashcp is used compared to just cp. I 
> noticed that flashcp writes in 4K blocks. The Macronix device has a 256 byte 
> page buffer. I have tried slowing down the bus to 5MHz and that made no 
> difference. Note that we are currently using single bit mode for both the host 
> and BMC processors for this flash, though we plan to move to move to QPI on 
> the host processor later.
> 
> Before the write operation the host processor has not had any access to the 
> SPI NOR. The host is powered down and the BMC is rebooted to force a clean 
> state.
> 

Did you find the problem? I've added Cédric to Cc in case you haven't - he
should be able to answer questions about the flash stack.

Andrew