Re: [Patch v6 1/4] memory: tegra: Add memory controller channels support

From: Ashish Mhetre
Date: Mon Apr 11 2022 - 03:28:55 EST




On 4/11/2022 12:03 PM, Dmitry Osipenko wrote:
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On 4/11/22 09:05, Ashish Mhetre wrote:


On 4/10/2022 7:48 PM, Dmitry Osipenko wrote:
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06.04.2022 08:24, Ashish Mhetre пишет:
+ num_dt_channels =
of_property_count_elems_of_size(pdev->dev.of_node, "reg",
+ reg_cells *
sizeof(u32));
+ /*
+ * On tegra186 onwards, memory controller support multiple
channels.
+ * Apart from regular memory controller channels, there is one
broadcast
+ * channel and one for stream-id registers.
+ */
+ if (num_dt_channels < mc->soc->num_channels + 2) {
+ dev_warn(&pdev->dev, "MC channels are missing, please
update memory controller DT node with MC channels\n");
+ return 0;
+ }
+
+ mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev,
"mc-broadcast");
+ if (IS_ERR(mc->bcast_ch_regs))
+ return PTR_ERR(mc->bcast_ch_regs);

Looks to me that you don't need to use of_property_count_elems_of_size()
and could only check the "mc-broadcast" presence to decide whether this
is an older DT.

Now that we are using reg-names in new DT, yes it'd be fine to just
check mc-broadcast to decide it's a new or old DT.

mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev,
"broadcast");
if (IS_ERR(mc->bcast_ch_regs)) {
dev_warn(&pdev->dev, "Broadcast channel is missing, please
update your
device-tree\n");
return PTR_ERR(mc->bcast_ch_regs);
}

return 0;

to avoid DT ABI break, right?

Yes, it should be "return 0".

But if we "return 0" from here, then what about the case when ioremap()
actually fails with new DT i.e. when broadcast reg is present in DT?
In that case error should be returned and probe should be failed, right?