Re: huge emmc speed regression

On 06/11/2021 12:58, Andriy Gapon wrote:
> 
> Upfront, I haven't tested the latest main / current yet.
> I should really test it but that's porbably for the next weekend.
> 
> I see a huge emmc speed difference between the current from April 2021 and 
> September 2021 (commit 5e79bba562bc303eed669dbd0d391b6c6a9c289b) on Orange Pi PC 
> Plus using on-board eMMC card.  I use MMCCAM in both cases.
> 
> In the old environment I see expected read speeds (with sequential dd) of around 
> 40 MB/s.
> In the new environment the speeds are around 300 KB/s (like a very good floppy 
> disk of old).
> 
> Some info from the old environment:
> # camcontrol mmcsdcmd 2:0:0 -I
> Host controller information
> Host OCR: 0x300000
> Min frequency: 400 KHz
> Max frequency: 52 MHz
[snip]

> Same command in the new environment looks a bit strange:
> # camcontrol mmcsdcmd 2:0:0 -I
> Host controller information
> Host OCR: 0x300000
> Min frequency: 400 KHz
> Max frequency: 0 MHz
[snip]

It seems that this is because the FDT does not have max-frequency property.
The old mmc_fdt_parse() code would leave f_max alone in that case and it was set 
to 52 MHz by the driver.
However, the new code in mmc_fdt_parse(), or rather mmc_parse(), would reset 
f_max to zero (despite the comment that was carried over):

         /*
          * max-frequency is optional, drivers should tweak this value
          * if it's not present based on the clock that the mmc controller
          * operates on
          */
         max_freq = 0;
         device_get_property(dev, "max-frequency", &max_freq, sizeof(uint64_t));
         host->f_max = max_freq;


-- 
Andriy Gapon