| Message ID | 201411111910.34231.juergen@kreuzholzen.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Nov 11, 2014 at 07:10:33PM +0100, Juergen Borleis wrote: > 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. I assume the system uses a device tree? This is the dm9000 driver? It doesn't seem to use clk stuff, but it should be possible to add an optional clk entry. Best regards Uwe
diff --git a/drivers/clk/samsung/clk-s3c64xx.c b/drivers/clk/samsung/clk-s3c64xx.c index 0f590e5..f7d2d57 100644 --- a/drivers/clk/samsung/clk-s3c64xx.c +++ b/drivers/clk/samsung/clk-s3c64xx.c @@ -404,6 +404,7 @@ static struct samsung_clock_alias s3c64xx_clock_aliases[] = { ALIAS(PCLK_IIS0, "samsung-i2s.0", "iis"), ALIAS(PCLK_AC97, "samsung-ac97", "ac97"), ALIAS(PCLK_TSADC, "s3c64xx-adc", "adc"), + ALIAS(MEM0_NFCON, NULL, "nand"), ALIAS(PCLK_KEYPAD, "samsung-keypad", "keypad"), ALIAS(PCLK_PCM1, "samsung-pcm.1", "pcm"), ALIAS(PCLK_PCM0, "samsung-pcm.0", "pcm"),
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. How to prevent this? Can we keep the "hclk_mem0" enabled without an active consumer? Or do we need a dummy consumer? Or do we need to request for "hclk_mem0" when at least one external device is attached? Or should we remove the "clock stop" feature for at least the S3C6410 SoC? With the patch below I was able to reproduce the behavior: Author: Juergen Borleis <juergen@kreuzholzen.de> Date: Mon Nov 10 23:35:06 2014 +0100 ARM/S3C6410/NAND: add clock alias to keep an old driver alive This change enables the existing S3c2410.c driver for the S3C6410. But keep in mind to disable the CONFIG_MTD_NAND_S3C2410_CLKSTOP when using this driver! Why? The access to external devices depends on a running "hclk_mem0" clock. As the NAND controller was the only single user of it, it disables it, when it disables its owm clock to save power. This locks the system. m( Signed-off-by: Juergen Borleis <juergen@kreuzholzen.de> jbe [1] drivers/mtd/nand/s3c2410.c