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Date: Thu, 17 Jun 2021 14:40:49 +0300
From: Mikko Perttunen <cyndis@...si.fi>
To: Greg KH <gregkh@...uxfoundation.org>,
Mikko Perttunen <mperttunen@...dia.com>
Cc: arnd@...db.de, ykaukab@...e.de, linux-tegra@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] misc: sram: Only map reserved areas in Tegra SYSRAM
On 6/17/21 2:00 PM, Greg KH wrote:
> On Thu, Jun 17, 2021 at 12:48:04PM +0300, Mikko Perttunen wrote:
>> On Tegra186 and later, a portion of the SYSRAM may be reserved for use
>> by TZ. Non-TZ memory accesses to this portion, including speculative
>> accesses, trigger SErrors that bring down the system. This does also
>> happen in practice occasionally (due to speculative accesses).
>>
>> To fix the issue, add a flag to the SRAM driver to only map the
>> device tree-specified reserved areas depending on a flag set
>> based on the compatibility string. This would not affect non-Tegra
>> systems that rely on the entire thing being memory mapped.
>>
>> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
>> ---
>> drivers/misc/sram.c | 108 +++++++++++++++++++++++++++++++-------------
>> drivers/misc/sram.h | 9 ++++
>> 2 files changed, 86 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
>> index 93638ae2753a..a27ffb3dbea8 100644
>> --- a/drivers/misc/sram.c
>> +++ b/drivers/misc/sram.c
>> @@ -97,7 +97,24 @@ static int sram_add_partition(struct sram_dev *sram, struct sram_reserve *block,
>> struct sram_partition *part = &sram->partition[sram->partitions];
>>
>> mutex_init(&part->lock);
>> - part->base = sram->virt_base + block->start;
>> +
>> + if (sram->config->map_only_reserved) {
>> + void *virt_base;
>> +
>> + if (sram->no_memory_wc)
>> + virt_base = devm_ioremap_resource(sram->dev, &block->res);
>> + else
>> + virt_base = devm_ioremap_resource_wc(sram->dev, &block->res);
>> +
>> + if (IS_ERR(virt_base)) {
>> + dev_err(sram->dev, "could not map SRAM at %pr\n", &block->res);
>> + return PTR_ERR(virt_base);
>> + }
>> +
>> + part->base = virt_base;
>> + } else {
>> + part->base = sram->virt_base + block->start;
>> + }
>>
>> if (block->pool) {
>> ret = sram_add_pool(sram, block, start, part);
>> @@ -198,6 +215,7 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
>>
>> block->start = child_res.start - res->start;
>> block->size = resource_size(&child_res);
>> + block->res = child_res;
>> list_add_tail(&block->list, &reserve_list);
>>
>> if (of_find_property(child, "export", NULL))
>> @@ -295,15 +313,17 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
>> */
>> cur_size = block->start - cur_start;
>>
>> - dev_dbg(sram->dev, "adding chunk 0x%lx-0x%lx\n",
>> - cur_start, cur_start + cur_size);
>> + if (sram->pool) {
>> + dev_dbg(sram->dev, "adding chunk 0x%lx-0x%lx\n",
>> + cur_start, cur_start + cur_size);
>>
>> - ret = gen_pool_add_virt(sram->pool,
>> - (unsigned long)sram->virt_base + cur_start,
>> - res->start + cur_start, cur_size, -1);
>> - if (ret < 0) {
>> - sram_free_partitions(sram);
>> - goto err_chunks;
>> + ret = gen_pool_add_virt(sram->pool,
>> + (unsigned long)sram->virt_base + cur_start,
>> + res->start + cur_start, cur_size, -1);
>> + if (ret < 0) {
>> + sram_free_partitions(sram);
>> + goto err_chunks;
>> + }
>> }
>>
>> /* next allocation after this reserved block */
>> @@ -331,40 +351,66 @@ static int atmel_securam_wait(void)
>> 10000, 500000);
>> }
>>
>> +static const struct sram_config default_config = {
>> +};
>
> No need for a "default" config, just do not provide one and then do not
> call it if it is not set. Much simpler and less code churn.
Sure, will do.
>
>
>> +
>> +static const struct sram_config atmel_securam_config = {
>> + .init = atmel_securam_wait
>
> Add a trailing , please.
Will do.
>
>> +};
>> +
>> +/*
>> + * SYSRAM contains areas that are not accessible by the
>> + * kernel, such as the first 256K that is reserved for TZ.
>> + * Accesses to those areas (including speculative accesses)
>> + * trigger SErrors. As such we must map only the areas of
>> + * SYSRAM specified in the device tree.
>> + */
>> +static const struct sram_config tegra_sysram_config = {
>> + .map_only_reserved = true,
>> +};
>> +
>> static const struct of_device_id sram_dt_ids[] = {
>> - { .compatible = "mmio-sram" },
>> - { .compatible = "atmel,sama5d2-securam", .data = atmel_securam_wait },
>> + { .compatible = "mmio-sram", .data = &default_config },
>> + { .compatible = "atmel,sama5d2-securam", .data = &atmel_securam_config },
>> + { .compatible = "nvidia,tegra186-sysram", .data = &tegra_sysram_config },
>> + { .compatible = "nvidia,tegra194-sysram", .data = &tegra_sysram_config },
>> {}
>> };
>>
>> static int sram_probe(struct platform_device *pdev)
>> {
>> + const struct sram_config *config;
>> struct sram_dev *sram;
>> int ret;
>> struct resource *res;
>> - int (*init_func)(void);
>> +
>> + config = of_device_get_match_data(&pdev->dev);
>>
>> sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
>> if (!sram)
>> return -ENOMEM;
>>
>> sram->dev = &pdev->dev;
>> + sram->no_memory_wc = of_property_read_bool(pdev->dev.of_node, "no-memory-wc");
>> + sram->config = config;
>> +
>> + if (!config->map_only_reserved) {
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + if (sram->no_memory_wc)
>> + sram->virt_base = devm_ioremap_resource(&pdev->dev, res);
>> + else
>> + sram->virt_base = devm_ioremap_resource_wc(&pdev->dev, res);
>> + if (IS_ERR(sram->virt_base)) {
>> + dev_err(&pdev->dev, "could not map SRAM registers\n");
>> + return PTR_ERR(sram->virt_base);
>> + }
>>
>> - res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> - if (of_property_read_bool(pdev->dev.of_node, "no-memory-wc"))
>> - sram->virt_base = devm_ioremap_resource(&pdev->dev, res);
>> - else
>> - sram->virt_base = devm_ioremap_resource_wc(&pdev->dev, res);
>> - if (IS_ERR(sram->virt_base)) {
>> - dev_err(&pdev->dev, "could not map SRAM registers\n");
>> - return PTR_ERR(sram->virt_base);
>> + sram->pool = devm_gen_pool_create(sram->dev, ilog2(SRAM_GRANULARITY),
>> + NUMA_NO_NODE, NULL);
>> + if (IS_ERR(sram->pool))
>> + return PTR_ERR(sram->pool);
>> }
>>
>> - sram->pool = devm_gen_pool_create(sram->dev, ilog2(SRAM_GRANULARITY),
>> - NUMA_NO_NODE, NULL);
>> - if (IS_ERR(sram->pool))
>> - return PTR_ERR(sram->pool);
>> -
>> sram->clk = devm_clk_get(sram->dev, NULL);
>> if (IS_ERR(sram->clk))
>> sram->clk = NULL;
>> @@ -378,15 +424,15 @@ static int sram_probe(struct platform_device *pdev)
>>
>> platform_set_drvdata(pdev, sram);
>>
>> - init_func = of_device_get_match_data(&pdev->dev);
>> - if (init_func) {
>> - ret = init_func();
>> + if (config->init) {
>> + ret = config->init();
>> if (ret)
>> goto err_free_partitions;
>> }
>>
>> - dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
>> - gen_pool_size(sram->pool) / 1024, sram->virt_base);
>> + if (sram->pool)
>> + dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
>> + gen_pool_size(sram->pool) / 1024, sram->virt_base);
>>
>> return 0;
>>
>> @@ -405,7 +451,7 @@ static int sram_remove(struct platform_device *pdev)
>>
>> sram_free_partitions(sram);
>>
>> - if (gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
>> + if (sram->pool && gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
>> dev_err(sram->dev, "removed while SRAM allocated\n");
>>
>> if (sram->clk)
>> diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
>> index 9c1d21ff7347..d2058d8c8f1d 100644
>> --- a/drivers/misc/sram.h
>> +++ b/drivers/misc/sram.h
>> @@ -5,6 +5,11 @@
>> #ifndef __SRAM_H
>> #define __SRAM_H
>>
>> +struct sram_config {
>> + int (*init)(void);
>> + bool map_only_reserved;
>> +};
>> +
>> struct sram_partition {
>> void __iomem *base;
>>
>> @@ -15,8 +20,11 @@ struct sram_partition {
>> };
>>
>> struct sram_dev {
>> + const struct sram_config *config;
>> +
>> struct device *dev;
>> void __iomem *virt_base;
>> + bool no_memory_wc;
>
> What does "wc" here mean?
Writecombine. The code in _probe checks for the "no-memory-wc" flag in
device tree and if it's set it uses devm_ioremap_resource instead of
devm_ioremap_resource_wc. Now that the ioremap call can happen outside
of _probe we need to save this property.
>
> thanks,
>
> greg k-h
>
Thank you, will send a v2 with changes.
Mikko
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