Re: [PATCH 0/6] RISC-V: Add eMMC support for TH1520 boards

[Robert Nelson]

On Fri, Sep 22, 2023 at 2:08 PM Robert Nelson <robertcnelson@xxxxxxxxx> wrote:
>
> On Thu, Sep 21, 2023 at 8:51 PM Drew Fustini <dfustini@xxxxxxxxxxxx> wrote:
> >
> > This series adds support for the eMMC on the BeagleV Ahead and the
> > Sipeed LicheePi 4A. This allows the kernel to boot with the rootfs on
> > eMMC.
> >
> > I tested on top of v6.6-rc2 with this config [1]. I was able to boot
> > both the Ahead [2] and LPi4a [3] from eMMC. The following prerequisites
> > are required:
> >
> >   [PATCH v2] riscv: dts: thead: set dma-noncoherent to soc bus [4]
> >
> > I pushed a branch [5] with this patch series and the above patch for
> > those that find a git branch easier to test.
> >
> > Please note that only the MMC controller connected to the eMMC device
> > is enabled in the device trees for these two boards. I did not yet
> > attempt to configure and use the microSD card slot. My preference is to
> > address that in a future patch series.
> >
> > References:
> > [1] https://gist.github.com/pdp7/5fbdcf2a65eb1abdd3a29d519c19cdd2
> > [2] https://gist.github.com/pdp7/91a801a5f8d1070c53509eda9800ad78
> > [3] https://gist.github.com/pdp7/1445c3c991e88fd69c60165cef65726a
> > [4] https://lore.kernel.org/linux-riscv/20230912072232.2455-1-jszhang@xxxxxxxxxx/
> > [5] https://github.com/pdp7/linux/tree/b4/th1520-mmc
>
> This patchset came out very nice!
>
> v6.6-rc2 with Last RFC v2:
>
> [    4.066630] mmc0: SDHCI controller on ffe7080000.mmc
> [ffe7080000.mmc] using PIO
>
> debian@BeagleV:~$ sudo hdparm -tT /dev/mmcblk0
>
> /dev/mmcblk0:
>  Timing cached reads:   1516 MB in  2.00 seconds = 758.09 MB/sec
>  Timing buffered disk reads:  84 MB in  3.01 seconds =  27.94 MB/sec
>
> vs v6.6-rc2 with this patchset:
>
>  [    4.096837] mmc0: SDHCI controller on ffe7080000.mmc
> [ffe7080000.mmc] using DMA
>
> debian@BeagleV:~$ sudo hdparm -tT /dev/mmcblk0
>
> /dev/mmcblk0:
>  Timing cached reads:   1580 MB in  2.00 seconds = 790.97 MB/sec
>  Timing buffered disk reads: 418 MB in  3.00 seconds = 139.11 MB/sec

Drew pointed out on Slack, this was not quite right.. After more
digging by Drew, CONFIG_DMA_GLOBAL_POOL is causing a DMA limitation
with the multiplatform defconfig. so with,

./scripts/config --disable CONFIG_ARCH_R9A07G043

(to remove CONFIG_DMA_GLOBAL_POOL)... another 2x in buffered reads..

[    4.059242] mmc0: SDHCI controller on ffe7080000.mmc
[ffe7080000.mmc] using ADMA 64-bit

debian@BeagleV:~$ sudo hdparm -tT /dev/mmcblk0

/dev/mmcblk0:
 Timing cached reads:   1600 MB in  2.00 seconds = 800.93 MB/sec
 Timing buffered disk reads: 892 MB in  3.00 seconds = 297.06 MB/sec

Regards,

-- 
Robert Nelson
https://rcn-ee.com/