lkml.org 
[lkml]   [2019]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] mmc: sdhci: sdhci-pci-o2micro: Check if controller supports 8-bit width
On Wed, Jun 12, 2019 at 04:09:47PM +0300, Adrian Hunter wrote:
> On 10/06/19 9:53 PM, Raul E Rangel wrote:
> > The O2 controller supports 8-bit EMMC access. mmc_select_bus_width()
> > will be used to determine if the MMC supports 8-bit or 4-bit access.
>
> The problem is that the bit indicates a host controller capability, not how
> many data lines there actually are on the board. Will this break something
> that does not have 8 lines?

So I asked the controller vendor about that:
> The capability shows the host controller can support 1,4,and 8 bit bus
> data transfer but it also depends on if HW can support it. Driver or FW
> should implement the bus testing procedure that is defined in A.6.3.a
> in JESD84-B51 spec to decide the real bus width that is supported in HW.

This seems to be what `mmc_select_bus_width()` is doing.

I don't actually have any 4-bit hardware to test with though.

Thanks for the review!

\
 
 \ /
  Last update: 2019-06-12 17:09    [W:0.051 / U:16.388 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site