Re: Samsung/S3C6410/Mini6410: how to handle NAND's "clock off"
From: Juergen Borleis <hidden>
Date: 2014-11-12 12:00:27
Also in:
linux-arm-kernel, linux-samsung-soc
On Wednesday 12 November 2014 10:14:58 Uwe Kleine-König wrote:
Hello again, [extending audience a bit] On Tue, Nov 11, 2014 at 07:42:26PM +0100, Uwe Kleine-König wrote:quoted
On Tue, Nov 11, 2014 at 07:10:33PM +0100, Juergen Borleis wrote:quoted
Hi, the S3C2410 NAND driver [1] can still be used for NANDs attached to an S3C6410 SoC. But this driver has a "nice" feature called "clock off" to save some power while not in use. I tried it here on my Mini6410 platform and it freezes the system. The clock tree is somehow: [...] hclk 4 4 133000000 0 0 hclk_mfc 0 0 133000000 0 0 hclk_mem0 2 2 133000000 0 0 mem0_srom 0 0 133000000 0 0 mem0_nfcon 1 1 133000000 0 0 mem0_onenand0 0 0 133000000 0 0 mem0_onenand1 0 0 133000000 0 0 mem0_cfcon 0 0 133000000 0 0 [...] On the Mini6410 the "mem0_nfcon" clock is the only single user of the "hclk_mem0". And this clock is required to keep the access to the external network device enabled. When the NAND driver disables its clock "mem0_nfcon", the "hclk_mem0" gets also disabled because there is no consumer anymore. The next time the network driver tries to access its device, the SoC freezes.Sounds like the network driver should hold a reference to hclk_mem0.After talking to Jürgen by phone, the solution that the dm9000 driver should handle the clock sounds wrong. The clk in question is needed by the SoC to operate the bus the dm9000 is connected to. So I think the right approach would include
I think we need the same here for the S3C6410 SoC, like the imx-weim driver is for i.MX SoCs. jbe -- Pengutronix e.K. | Juergen Borleis | Industrial Linux Solutions | Phone: +49-5121-206917-5128 | Peiner Str. 6-8, 31137 Hildesheim, Germany | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de/ |