Messages in this thread | | | Subject | Re: [PATCH v9 01/17] memory: tegra30: Support interconnect framework | From | Georgi Djakov <> | Date | Wed, 18 Nov 2020 17:30:22 +0200 |
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On 18.11.20 0:02, Dmitry Osipenko wrote: > 17.11.2020 23:24, Georgi Djakov пишет: >> Hi Dmitry, >> >> Thank you working on this! >> >> On 15.11.20 23:29, Dmitry Osipenko wrote: >>> Now Internal and External memory controllers are memory interconnection >>> providers. This allows us to use interconnect API for tuning of memory >>> configuration. EMC driver now supports OPPs and DVFS. MC driver now >>> supports tuning of memory arbitration latency, which needs to be done >>> for ISO memory clients, like a Display client for example. >>> >>> Tested-by: Peter Geis <pgwipeout@gmail.com> >>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com> >>> --- >>> drivers/memory/tegra/Kconfig | 1 + >>> drivers/memory/tegra/tegra30-emc.c | 349 +++++++++++++++++++++++++++-- >>> drivers/memory/tegra/tegra30.c | 173 +++++++++++++- >>> 3 files changed, 501 insertions(+), 22 deletions(-) >>> >> [..]> diff --git a/drivers/memory/tegra/tegra30.c >> b/drivers/memory/tegra/tegra30.c >>> index d0314f29608d..ea849003014b 100644 >>> --- a/drivers/memory/tegra/tegra30.c >>> +++ b/drivers/memory/tegra/tegra30.c >> [..] >>> + >>> +static int tegra30_mc_icc_set(struct icc_node *src, struct icc_node >>> *dst) >>> +{ >>> + struct tegra_mc *mc = icc_provider_to_tegra_mc(src->provider); >>> + const struct tegra_mc_client *client = &mc->soc->clients[src->id]; >>> + u64 peak_bandwidth = icc_units_to_bps(src->peak_bw); >>> + >>> + /* >>> + * Skip pre-initialization that is done by icc_node_add(), which >>> sets >>> + * bandwidth to maximum for all clients before drivers are loaded. >>> + * >>> + * This doesn't make sense for us because we don't have drivers >>> for all >>> + * clients and it's okay to keep configuration left from bootloader >>> + * during boot, at least for today. >>> + */ >>> + if (src == dst) >>> + return 0; >> >> Nit: The "proper" way to express this should be to implement the >> .get_bw() callback to return zero as initial average/peak bandwidth. >> I'm wondering if this will work here? >> >> The rest looks good to me! > > Hello Georgi, > > Returning zeros doesn't allow us to skip the initialization that is done > by provider->set(node, node) in icc_node_add(). It will reconfigure > memory latency in accordance to a zero memory bandwidth, which is wrong > to do. > > It actually should be more preferred to preset bandwidth to a maximum > before all drivers are synced, but this should be done only once we will > wire up all drivers to use ICC framework. For now it's safer to keep the > default hardware configuration untouched.
Ok, thanks for clarifying! Is there a way to read this hardware configuration and convert it to initial bandwidth? That's the idea of the get_bw() callback actually. I am just curious and trying to get a better understanding how this works and if it would be useful for Tegra.
Thanks, Georgi
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